HYP2018

Sunday, June 24, 2018

Monday, June 25, 2018

Continued Registration and Coffee

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  • In this opening talk at HYP2018 I will recall some old persistent problems in hypernuclear physics and related strange-particle physics that I encountered as a student, and how they have developed throughout the last 50 years in shaping one's contemporary perspective of Strangeness Nuclear Physics.
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Coffee break

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  • We extract hyperon forces from QCD on lattice by means of the HAL QCD method, and then apply them to hyperons in nuclear matter.

    Hyperon forces are interesting in many aspects. First, they are in the company of nuclear force. Therefor, it is necessary to know them in order to completely understand baryon- baryon interactions including nuclear force, e.g. why nuclear force has a strong repulsion at short distances and so on. However, hyperon forces are not revealed enough yet due to a shortage of experimental data.

    Second, hyperon forces are essential for physics of neutron star. High density baryonic matter is naturally expected to contain hyperons with a sizable fraction. However, recent discovery of massive neutron stars indicate a hard equation of state of neutron star matter, which is difficult to explain theoretically with a baryonic matter containing hyperons. This is one of the most challenging puzzle in modern physics.

    Conventionally, hyperon interactions are studied in models, e.g. meson exchange model. Though, there are uncertainties in the resulting interactions due to a deficiency of input data. A powerful method was invented in 2006 to extract nucleon-nucleon interaction from QCD on lattice. This HAL QCD method has been improved and widely extended to many other systems including general two-baryon systems. Namely, nowadays hyperon interactions can be derived from QCD without consulting experimental data.

    In my talk, first I will explain essence of the HAL QCD method. Then, I will show hyperon S-wave interaction potentials derived from QCD at almost the physical point. Finally, I will show some results of application of the QCD hyperon forces, including hyperon single-particle potentials in nuclear matter.

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  • Numerical evaluation of the quantum-mechanical correlation functions in the hypernuclear sector through the method of lattice QCD enables accessing scattering and transition amplitudes involving few nucleons and hyperons. Such studies constrain the low-energy effective interactions, and hence provide the input to ab initio many-body calculations of larger systems with phenomenological importance. Substantial progress has been achieved in lattice QCD studies of nuclei and hypernuclei in recent years, leading to the first predictions of a potentially bound H-dibaryon in nature, and the strength and nature of interactions in nucleon-hyperon channels of importance in dense matter - predictions that will be refined in upcoming years with the growth of computational resources devoted to these studies. In this talk, I report on recent results by the Nuclear Physics from Lattice QCD (NPLQCD) collaboration in constraining the hypernuclear interactions, albeit with quark that are heavier than those in nature, and will comment on the prospect and impact of calculations towards the physical point.

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  • The Nijmegen extended-soft-core ESC08c model for the baryon-baryon (BB) interactions of the SU(3) flavor-octet of baryons (N, Λ, Σ, and Ξ) is presented. In the spirit of the Yukawa-approach to the nuclear force problem, the interactions are studied from the meson-exchange picture viewpoint, using generalized soft-core Yukawa-functions. These interactions are supplemented with (i) multiple- gluon-exchange, and (ii) structural effects due to the quark-core of the baryons. The extended-soft- core (ESC) meson-exchange interactions consist of local- and non-local-potentials due to (i) One- boson-exchanges (OBE), which are the members of nonets of pseudoscalar, vector, scalar, and axial- vector mesons, (ii) diffractive (i.e. multiple-gluon) exchanges, (iii) two pseudo-scalar exchange (PS- PS), and (iv) meson-pair-exchange (MPE). The OBE- and MPE-vertices are regulated by gaussian form factors producing potentials with a soft behavior near the origin. The assignment of the cut-off masses for the BBM-vertices is dependent on the SU(3)-classification of the exchanged mesons for OBE, and a similar scheme for MPE. In addition to the ρ(770) and f0(620), also the kappa(861) has been treated as a broad meson.
    The ESC-model ESC16, as well as its predecessors ESC08 and ESC04, describe the nucleon- nucleon (NN), hyperon-nucleon (YN), and hyperon-hyperon (YY) interactions in a unified way using broken SU(3)-symmetry. Important non-standard ingredients in the OBE-sector in the ESC- models are (i) the axial-vector meson potentials, and (ii) a zero in the scalar- and axial-vector meson form factors. The meson couplings and F/(F+D)-ratio’s can be understood from the predictions of
    the 3P0-dominated quark-antiquark pair creation (QPC) model in the framework of the constituent quark model. SU(3)-symmetry serves to connect the N N with the Y N and the Y Y channels. In the fit to NN and YN many parameters are essentially fixed by the NN-data. A few, but severely constrained e.g. F/(F+D)-ratio’s, parameters are left for determination of the Y N -interactions and the  YYexperimental  indications.  In  particular,  the  meson-baryon  coupling  constants  are  SUf(3) symmetric. using the coupling constants of the N N ⊕ Y N -analysis as input.
    In establishing the parameters of the model a simultaneous fit to NN- and YN-channels has been
    performed. Here the information about ΛΛ, ΞN , and hypernuclei played an important role in the form of using constraints. In particular, the experimental indications for the ΛΛ-attraction, the Ξ-nuclear and the Σ-nuclear well-depth were directive. About 25 physical coupling parameters and 8 cut-off and diffractive masses, were searched. The obtained OBE-couplings and the F/(F + D)- ratio’s can be well understood in the context of the QPC-model.
    The simultaneous fit of the ESC-models to the NN- and YN- scattering data with a single set    of parameters has achieved excellent results for the NN- and YN-data, and for the YY-data in accordance with the experimental indications for ΛΛ and ΞN . In the case of the most recent ESC- model, called ESC16, the achievements are: (i) For the selected 4313 pp and np scattering data
    2
    with  energies  0  ≤  Tlab≤  350  MeV,  the  model  reaches  a  fit  having  χ  /Ndata=  1.10.   (ii)  The
    deuteron binding energy and all the NN scattering lengths are fitted very nicely. (iii) The YN-data
    are described very well with χ2/N      = 1.11, giving at the same time good descriptions of the Λ,
    data
    Σ, and Ξ nuclear well-depths. (iv) The model has no bound states for S=-1,-2,-3,-4. (v) The nuclear saturation, and well-depths UΣ, UΞ need important contributions from three-body forces.

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Lunch break - on your own

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  • Λ-Proton elastic scattering offers multiple insights on problems in nuclear physics. SU(3)-flavor symmetry implies a close agreement between the Λ-proton and proton- proton scattering cross sections. The Λ-Proton elastic scattering cross section can also illuminate the structure of neutron stars. A data-mining project was started using multiple CLAS data sets taken for other purposes with photon beams on a long liquid hydrogen target. A Λ produced in a process such as γ p → K+Λ can interact with a second proton inside the target before either decaying or leaving the target. The good angular acceptance and momentum resolution of CLAS make it well-suited for this type of analysis, even though it was not designed for a measurement such as this. The scattered Λ can be found in the π- + proton invariant mass. The four-vector of the initial Lambda is then reconstructed in the process Xp → Λp, which shows a strong peak at the Lambda mass with roughly twice the number of events as the existing world data sample. This observation opens up the possibility of other measurements using secondary beams of short-lived particles. This talk will discuss the current status of the analysis, and our plans for future work on this project.

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  • The study of hadron-hadron interactions can be best accessed via scattering experiments. This technique worked very well with nucleons and also secondary pion- and kaon-beams but becomes a real challenge for short-lived hadrons, in particular for hyperons. Since the hyperon-nucleon and also hyperon-nucleon-nucleon interaction is scarcely known and plays a fundamental role in the understanding of the equation of state of dense baryonic matter, new experimental techniques are called for. In this talk we review recent results from femtoscopy studies of pp and pΛ correlations measured in p-Nb reactions at 3.5 GeV and pp, p-Λ, Λ-Λ and pΞ correlations extracted from pp collisions at 7 and 13 TeV and p-Pb collisions at 5.02 TeV, measured by the HADES and ALICE collaboration, respectively. We will discuss the advantages of studying baryon-baryon correlations in small colliding systems, showing the feasibility and limits of the method and giving an overview of the newly developed tools capable of computing the exact correlation function for any colliding system. We will present current results and future perspective at the LHC and at FAIR.

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  • No published data on Λn scattering exist. A relativistic heavy-ion experiment has suggested that a Λnn bound state has been seen [1]. Were that the case, our knowledge of the nn interaction would permit us to use the Λnn bound state to provide strong constraints on the Λn interaction. JLab would be an ideal facility to obtain such data using the 3H(e,e’K+)3 n reaction. However, four theoretical analyses based upon pairwise nn and Λn interactions, including our own, have cast serious doubt on the bound-state assertion [2-5]. Nevertheless, there could exist a three-body resonance in the Λnn system. Such a resonance could also be used to rigorously constrain the Λn interaction.

    We will discuss calculations of the Λnn system using pairwise interactions of rank one, separable form that fit effective range parameters of the nn system and those predicted for the yet-to-be observed Λn system by two different Nijmegen one-boson exchange potentials [6,7], the Ju¨lich one-boson exchange potential [8] and a chiral ΛN potential [9] based upon the known Λp scattering data. The use of rank one separable potentials allows us to analytically continue the Λnn Faddeev equations into the second complex energy plane in search of resonance poles, by examining the eigenvalue spectrum of the kernel of the Faddeev equations.

    Although none of the potentials examined, based upon the nominal Λp scattering length and effective range, predict a true resonance pole, scaling of the Λn interaction by as little as 5% (well within the Λp scattering data uncertainties), would produce a resonance in the Λnn system. This suggests that one may use photo (electro) production of the Λnn system as a tool to examine the strength of the Λn interaction. In particular, K+ electro production from tritium at Jefferson Lab would be a means to explore the Λnn final state (resonance or sub-threshold resonance); modeling the position and width of the spectrum would provide significant constraints on the scattering length and effective range of the heretofore un-measured Λn interaction.

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Coffee break

Topical Session 1: Neutral Baryonic Systems with Strangenes

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  • Recently, the existence of two neutral bound baryonic systems has been suggested: signals for a bound or weakly unbound tetra-neutron were found at RIKEN, the HypHI experiment at GSI Darmstadt provided a hint for a bound strange nn-lambda system. In this introduction to the topical session bound neutral systems I will briefly recall the experimental results and the theoretical challenges which are posed by these observations. I will also address possibe consequences for doubly strange systems which may be searched for by the future PANDA experiment.
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  • The possible existence of neutral stable bound states composed of nucleons and strange particles will be discussed. In particular, putting special emphasis in the three- and four- body systems neutron-neutron-Lambda and neutron-neutron-Lambda-Lambda.
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  • Since the observation of Ξ hypernucleus, Kiso event, it is requested what kinds of Ξ hypernuclei should be observed as bound states in the future at J-PARC. As light Ξ hypernuclei, I propose to perform a search experiment of nnΞ and nnnΞ systems using 3He and 4He targets. In this conference, from the observation what kinds of ΞN part we can get to extract information.
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  • Study of few neutron systems is one of fundamental subjects in nuclear physics. We have found a candidate resonant tetraneutron in an exothermic double-charge exchange reaction 4He(8He, 8Be) at 190 A MeV. Production mechanism with kinematical consideration is introduced, where amounts of energy and momentum transfers in the reaction are emphasized. An analysis procedure on the four-body continuum system is presented and nuclear forces relevant for formation are discussed. Recent experimental results are also shown.
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  • We will review, from the theoretical point of view [3-13], the possible existence of bound or narrow resonant states in the three- and four-neutron systems, as suggested by a recent experimental result obtained at RIKEN [1] in the double charge exchange reaction 4He(8He, 8Be)4n at 186 MeV/u as well as in some preceding results [2].
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Tuesday, June 26, 2018

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  • One of the most important purposes of strange nuclear physics is to investigate the Baryon Baryon (BB) interaction. This is because the BB interaction is the basic interaction to describe a system including hyperons such as hypernuclei and high density matter in neutron stars. The understanding of the BB interaction also becomes a key to understand the origin of the short range repulsive cores in nuclear force and the BB interaction.
    In order to investigate ΣN interaction, we proposed a Σp scattering experiment (J-PARC  E40)  to measure differential cross sections of the Σ+p, Σ−p elastic scatterings and the Σ−p → Λn inelastic scattering in the momentum range of 400 < p (MeV/c) < 700. The physics motivation is to verify the large repulsive force due to Pauli effect in the  quark level in the Σ+p channel.  We also investigate the ΣN interaction systematically by separating isospin channels.
    The Σp scattering experiment (J-PARC E40) is just launched in the K1.8 beamline at J-PARC.  In the experiment, we detect two successive reactions of the Σ production by the πp → K+Σ reaction and the Σp scattering with  magnetic  spectrometers  (the  KURAMA  spectrometer) and recoiled proton detector (CATCH), respectively. CATCH is a key detector for E40 and consists of a cylindrical fiber tracker (CFT), BGO calorimeter and scintillation hodoscope.     The trajectory and kinetic energy of the recoiled proton are measured by CFT and BGO calorimeter, respectively, to identify the Σp scattering event. We have already completed the construction of CATCH and also have performed a commissioning experiment by using a 80 MeV proton beam at the cyclotron facility in Tohoku  university.  CATCH  could identify the    pp and pC scattering events from CH2 target successfully. In order to identify the πp → K+Σ reaction, the KURAMA spectrometer is utilized, which is suitable to detect a large number of K+ events thanks to its large acceptance and short flight length of ∼3 m. Present the KURAMA spectrometer has been rearranged to the E40 experimental configuration and CATCH has also been installed at the upstream of the KURAMA spectrometer.
    In January and February 2018, we have performed a commissioning experiment to check the detector system  in  a few  days of beam times.  Presently we  are analyzing data to  evaluate   the performance of both the KURAMA spectrometer  and  CATCH.  In  this  talk,  we would like to introduce our experiment at J-PARC and also report the results obtained from the commissioning experiment. Then we would like to talk the future prospects.

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  • In a physics world focused on dark matter, gravitational waves, and heavy photons, hadron processes and nuclear systems focusing on strangeness does not garner as much attention. However, the search for undiscovered states of the nucleon continues to yield interesting results. A large effort was done using the now defunct CEBAF Large Acceptance Spectrometer (CLAS) detector at the Thomas Jefferson National Accelerator Facility (JLab) to provide the database, which will allow for nearly model-independent partial wave analyses (PWA) to be carried out in the search for such states. Polarization observables provide a crucial role in the effort, as they are essential in disentangling the contributing resonanat and non-resonant amplitudes. Recent coupled-channel analyses have found strong sensitivity of the kaon hyperon channels to several higher mass nucleon resonances. Various experiments over the years were taken at JLab using circularly and linearly polarized tagged photons incident on a longitudinally and transversely polarized frozen spin butanol target (FROST), liquid hydrogen or deuterium, or a hydrogen deuteride target (HD-Ice) with the reaction products detected in CLAS. The works will be compared to predictions of recent multipole analyses. These results will significantly broaden the world database for these reactions.

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  • The mechanism of baryon-antibaryon photoproduction has not been extensively studied. Little is known about the dominant exchanges in the t-channel or the nature of baryon- like exchanges in the u-channel. At GlueX, we are studying the reactions γ p  BBp, where BB includes ΛΛ and pp. Kinematic fitting is used for the ΛΛ channel to extract the 5-body final states with Λ  π- p and Λ  π+ p. Data have been obtained from the respective reaction thresholds up to a beam energy of about 11 GeV. Photons in the energy range between 8.4 and 9 GeV were linearly polarized, allowing examination of observables like the beam spin asymmetry. Preliminary spectra from data obtained in Spring 2016 and Spring 2017 will be shown for the angular correlations among the produced particles. Our goal is to use spin correlations between the Λ hyperons to determine the angular momentum structure of the strangeness production mechanism.

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Coffee break

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  • Hypernuclei provide a natural and accessible laboratory to study hyperon-nucleon interaction and the impurity effect of hyperon in nuclear medium, which are relevant for understanding the structure of neutron stars. Building a connection between the accumulated data of γ-ray and reaction spectroscopic experiments on hypernuclei and the hyperon-nucleon interaction is our main task, even though this connection relies on nuclear many-body methods.
    Self-consistent mean-field approaches have been extensively adopted for hypernuclear structure since decades ago. Several interesting phenomena about hyperon impurity effect have been disclosed, such as the shrinkage of nuclear size, the modification of nuclear equilibrium shapes, the reduction of fission-barrier height in heavy nuclei, and the extension of nucleon driplines.
    Nevertheless, the constraints on the mean-field approaches from the hypernuclear data are mostly limited to the hyperon separation energies and the hyperon spin-orbit splitting. To overcome the difficulty of interpreting the rich hypernuclear spectroscopic data based on the mean-field approaches, one has to go beyond the mean-field approximations. It is particularly important for deformed or transitional hypernuclei where we expect to disclose novel interplay between hyperon and nuclear collective motions.

    In this talk, I will overview the progress on the relativistic mean-field approaches for Lambda hypernuclei with axially deformed, triaxially deformed or octuple deformed shapes. In particular, I will introduce the recent developments on the beyond mean-field studies of hypernuclear low-lying states. Finally, I will propose an ab-initio generator coordinate method calculation of deformed/ transitional hypernuclei in medium-mass region based on chiral nuclear forces.

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  • A Λ-nucleon Skyrme force suitable for reproducing the observed binding energies of the whole range of known light and heavy single-Λ hypernuclei is presented. Notable exceptions are identified and examined in comparison with a cluster model for the hypernuclear structure. The approach is extended to Cascade hypernuclei and compared with current experimental data.

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  • In this talk we present a calculation of the spectral function of the Λ hyperon in finite nuclei which is obtained from the corresponding Λ self-energy constructed within a perturbative many-body approach using some of the hyperon-nucleon interactions of the Juelich and Nijmegen groups. Binding energies, wave functions and disoccupation numbers of different single-particle states are obtained for various hypernuclei from 5ΛHe to ²⁰⁹ Pb. The agreement between the calculated binding energies and experimental data is qualitatively good. The small spin-orbit splitting of the p-, d-, f- and g-wave states is confirmed. The discrete and the continuum contributions of the single-Λ spectral function are computed. Their appearance is qualitatively similar to that of the nucleons. The Z- factor, that measures the importance of correlations, is also calculated. Our results show that its value is relatively large, indicating that the Λ hyperon is less correlated than nucleons. This is in agreement with the results obtained by other authors for the correlations of the Λ in infinite nuclear matter. The disoccupation numbers are obtained by integrating the spectral function over the energy. Our results show that the discrete contribution to the disoccupation number decreases when increasing the momentum of the Λ. This indicates that, in the production reactions of hypernuclei, the Λ hyperon is mostly formed in a quasi-free state.

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Lunch break - on your own

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  • In 2015, the first hypernuclear gamma-ray spectroscopy experiment at J-PARC has been completed. In this experiment (J-PARC E13), K- beams of 1.5 GeV/c and 1.8 GeV/c are transported through the K1.8 beam line and delivered to a liquid hydrogen target and liquid CF4 target, respectively, to populate 4ΛH and 19 F. In the first half of this contribution, some of the results from the E13 experiment will be highlighted. From the precise determination of the spin-flip gamma transition from the first excited 1+ state to the 0+ ground state, a sizable charge symmetry breaking effect in ΛN interaction in comparison to NN interaction has been experimentally confirmed, which awaits full theoretical explanation to this day. On the other hand, low-lying energy levels of sd-shell 19 F are identified. In particular, the energy splitting of the ground state spin doublet is determined providing the first look into the strength of spin-spin ΛN interaction in the sd- shell sector. The second half of the presentation pertains the future gamma-ray spectroscopy experiments at J-PARC, namely the last phase of the E13 experiments with some twist. The planned experiment (J-PARC E63) will take place at the K1.1 beam line with a setup almost identical to that for E13. 7ΛLi will be populated for lifetime measurement of the ground state spin-doublet transition, from which a B(M1) value should be extracted and eventually leads to g-factor of Λ in nuclear medium. Another objective of E63 is to determine the energy spacing of the ground state spin doublet in 4ΛH, mirror hypernucleus to 4ΛHe. The new measurement will establish the A=4 hypernuclear system on more experimentally solid ground for the investigation into the origin of the large charge symmetry breaking in ΛN interaction. An overview of the current preparation status of the E63 experiment will be discussed.

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  • Spectroscopic study of electro-produced Lambda hypernuclei has started at Jefferson Lab in the last year of the 20th century. Though it is known that spectroscopy of electro- produced hypernuclei has unique feature over other meson-produced hypernuclear spectroscopy, there exist many experimental difficulties such as small production cross- section, huge electron background and so on.

    We, finally, established the Lambda hypernuclear spectroscopy with electron beam by introducing novel experimental techniques and efforts of more than a decade. JLab hypernuclear collaboration is now preparing for a new experiment (JLab E12-15-008) to investigate isospin dependence of Lambda hypernuclei with 40Ca and 48Ca targets.

    I will overview unique feature of previously carried out hypernuclear study with electron beams at JLab. Physics goal and preparation status of the new experiment and future prospect of hypernuclear study with electron beams will be also discussed.

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Coffee break

Topical Session 2: Charge Symmetry Breaking

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  • As is well known, the Charge Symmetry of the strong interaction requires that nn and pp interaction strengths are equal. As a consequence, the en- ergy levels of nuclear isospin multiplets are expected to be identical, after correcting for the Coulomb energy difference. The breaking of this sym- metry manifests itself in experiments at a level of 0.07 MeV for the N N interaction in normal, not strange, nuclei. In Λ hypernuclei, where the ΛN interaction acts, the breaking is predicted to be 0.05 MeV by theoretical models which do not consider the effects of ΛN ΣN coupling and of the three-body ΛN N forces. However, from the experimental side, a large value of binding energy difference has been found for the A=4 isospin doublet, 4 H - 4 He, in experiments based on emulsion Λ Λ techniques in the seventies. The same experiments gave also indications about the binding energy difference in A=7, 8, 10, 12 isomultiplets which did not show a substantial breaking effect. In the last few years, several magnetic spectrometers provided high preci- sion results in the field of Hypernuclear Physics. In particular, the accurate determination of the Λ-binding energy for A=7, 10, 12, 16 systems con- tributed to stimulate considerably the discussion about the Charge Symme- try Breaking effect in Λ-hypernuclei isomultiplets. Also for the A=4 isospin doublet, very precise measurements of 4 H ground state binding energy and of 4 He first excited state energy have been obtained. My contribution aims at making an overview, focusing on recent exper- imental results and analyses, to introduce the discussion on the involved experimental aspects and on the recent theoretical calculations on Charge Symmetry Breaking in s− and p−shell Λ-hypernuclei.

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  • In contrast to the situation for the A=4 hypernuclei, there is little definitive evidence for charge-symmetry breaking in p-shell hypernuclei. Nevertheless, I will explore what Λ-Σ coupling and the introduction of differences between the Λ-p and Λ-n interactions can provide.

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  • Charge symmetry in hadron physics is broken in QCD by the up-down quark mass difference and electromagnetic interactions. In Λ hypernuclei, charge symmetry breaking (CSB) manifests itself in a sizable charge dependence of Λ separation energies of light mirror hypernuclei. The large value of CSB was recently reaffirmed by precision measurements of A = 4 hypernuclei [1, 2] and until recently it could not be reproduced in any ab initio 4-body calculation. In this contribution, I will report on our ab initio no-core shell model calculations of 4 He and 4 H using realistic nucleon-nucleon, three-nucleon and hyperon-nucleon interactions derived from chiral effective field theory plus a CSB Λ-Σ0 mixing vertex [3, 4]. Our calculations provide, for the first time, microscopic understanding of the sizable CSB in A = 4 hypernuclei.

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  • The charge symmetry breaking (CSB) effect reported in the A=4 mirror hypernuclei       is one of the hot topics in strangeness nuclear physics. Precise gamma-ray spectroscopy with an energy resolution of a few keV is a powerful  tool  to  investigate  such  an  effect. Recently, a gamma-ray spectroscopy study of 4ΛHe was performed at the J-PARC K1.8 beam line (J-PARC E13) for this purpose. 4ΛHe hypernuclei were produced by the
    (K-, π-) reaction with a 1.5 GeV/c kaon beam. The excitation energy of first excited state of 4ΛHe (1+) was successfully determined to be 1.406 ± 0.004 MeV. On the other hand, that of the mirror hypernucleus (4ΛH) was reported as 1.09 ± 0.02 MeV in average from old studies. By comparing these results, we conformed the existence of CSB effect in the excitation energy.

    Reported values of the excitation energy (Ex [4ΛH (1+)]) in old studies show rather large deviation. In these measurements, the energy accuracy was limited by statistics and      the gamma-ray response function including the resolution as well as the Doppler broadening effect. Therefore, our next step is a more precise measurement of the excitation energy of 4ΛH (1+) to experimentally establish the A=4 mirror hypernuclei system. We are planing a gamma-ray spectroscopy of 4ΛH at the J-PARC K1.1 beam line
    (J-PARC E63) via the 6Li(K-, π-) reaction. We selected the SKS spectrometer system for tagging the reaction, which is common with the previous J-PARC E13. The gamma-ray energy will be measured with a Ge detector array, Hyperball-J, of which performance was already established.

    An outline of the J-PARC E63 experiment will be given in this contribution.

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  • We performed spectroscopy of 7ΛHe and 10 Be with the (e, e’K+) reaction at JLab Hall C. The ground state binding energies of these hypernuclei provides insights into the p-shell CSB by comparing isotopic mirror partners. In the latest hypernuclear experiment, JLab E05-115, we could successfully update the binding energies with a smaller error than that in old data. In this talk, I will present experimental techniques to accurately determine the Λ binding energy and results of 7ΛHe and 10 Be.

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  • Nuclear emulsion is a tracking detector with sub-micron spatial resolution. The nuclearemulsion has a potential to measure binding energies of mirror hypernuclei such as 4 Hand 4 He directly. The binding energies provide valuable information for charge symmetry braking (CSB) in Λ-N interaction. In the nuclear emulsion experiment in the 1960s and 1970s, the binding energies of light hypernuclei were measured. For example, the difference of binding energy of mirror hypernuclei (4 He - 4 H) was measured as +0.35 ± 0.04 MeV. Analysis of the nuclear emulsion plate for hypernuclei experiment is performed by the following method. We search for hypernuclei events and measure the range and angle of these tracks with high positional and angular accuracy. In the past experiments, the range and angle were measured manually. From the 1970s, microscopic images were read out from the image sensor and displayed on the CRT. An automated stage was developed to move the nuclear emulsion plate to a specific coordinate. These developments greatly shortened the analysis time. In the 2010s, with the development of computer graphics technology, the selection of events with a vertex, which is a characteristic of hypernuclei events, has been automated. This read-out system, called Vertex-Picker, achieved a read-out speed (volume per hour) of 100 times compared to the previous manual search. In addition, an automated track following method have been developed instead of following manually. These developments increased the number of hypernuclei events dramatically. KEK-PS E373 experiment, that is a hypernuclei experiment with nuclear emulsion, was conducted in 1999. The few double hypernuclear events identified so far showed that the Λ-Λ interaction is a weak attractive interaction. The J-PARC E07 experiment, which is the latest hybrid emulsion experiment, is expected to increase the number of double hypernuclei by a factor of 10 as compared to the E373 experiment. The exposure with a 1.8 GeV/c K- beam was completed in July 2017, the photographic development was completed in February 2018, and the analysis of the nuclear emulsion is currently carried out. We also search the whole volume of this nuclear emulsion for hypernuclei event candidates (with two vertexes) using the Vertex-Picker. In this talk, I will report the summary of past experiments, the development of recent emulsion technology, and the expected outcome on CSB from E07 experiment.

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  • The main objective of this contribution is to provide a framework for a panel discussion in the topical session on charge symmetry breaking in light hypernuclei.
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Wednesday, June 27, 2018

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  • The cross sections of electroproduction of p-shell hypernuclei were calculated in the distorted-wave impulse approximation. Previous calculations performed in the last two decades were updated utilizing new elementary-production amplitudes and new nucleus- hypernucleus structure based on the Shell model calculations. Predictions for the cross sections and excitation-energy spectra of the 9ΛLi, 12 B, and 16 N hypernuclei will be compared with the data from JLab experiments and an uncertainty of the theoretical results will be discussed. We will focus on the uncertainty from the elementary amplitude and the one-body density matrix.

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• (Abstract |

  • Recently hypernuclear reaction spectroscopy has progressed greatly by the (e, e′K+) experiments done at the Jefferson National Laboratory[1,2,3]. The high resolution of ∆E 0.5 MeV and the reliable binding energy determination provide us with a nice merit in understanding hypernuclear structure details. Among others, first, we foccus our attention to a new bump observed at EΛ 0 MeV in the 10B(e, e′K+)10Be experiment [3], because the other sharp and pronouced four peaks have been already predicted by the ‘standard’ calculations. In order to describe such new peak, we extend the model space by employing the multi-configuration wave functions with nuclear core parity mixing mediated by the Λ hyperon. They are re-expressed in terms of the coupled forms of the nuclear core eigenstates {ψc(Jc±; n)} and the Λ hyperon states as

    (10 Be; J􀀀) = Σ i i[ c(J􀀀 c ; n)  s](i) J + Σ i i[ c(J+ c ; n)  p](i) J (10 Be; J+) = Σ i ′ i[ c(J􀀀 c ; n)  p](i) J + Σ i ′ i[ c(J+ c ; n)  s](i) J

    By such extension the new peak at EΛ 0 MeV is successfully explained for the first time as shown in Fig. 1 for EL=1.5 GeV and θL =7 deg. This new peak manifests a γ K genuine hypernuclear state realized by the unique role of Λ participation which causes nuclear core parity mixing (major shell mixing). The similar extended calculations with multi-configuration wave functions are applied to other p-shell hypernuclei. In the second half, we will discuss the theoretical spectra of photoproduction pre- dicted for some typical medium-mass hypernuclei such as 40K and 48K in support of the Λ Λ experiments planned at JLab. For that purpose in general we adopt the same DWIA framework which has been applied previously to the photoproduction cross section es- timates of 28Si, 48V, 208Tl, etc. It is interesting to predict behaviors of the pronounced Λ Λ Λ peak positions depending remarkably on both proton and Λ single-particle energies.

• | Presentation)

• (Abstract |

  • Recently, the Kiso event was observed as a bound state. From the data, we found that ΞN interaction should be attractive. Furthermore, it is planned to measure Ξ binding energy using 12C target by (K-, K+) reaction. Now it is requested to extract informaion on ΞN interaction from the data. In the conference, within the framework of α+α+t+Ξ four-body model, I will discuss on this issue.

• | Presentation)

Coffee break

• (Abstract |

  • We have measured an excitation energy spectrum of the 12C(K-, K+)X reaction at 1.8 GeV/c with an energy resolution of 5.4 MeV (FWHM), which is the best energy resolution ever achieved in studying this reaction. The measurement was performed at the K1.8 beam line of the J-PARC hadron experimental hall by using the SKS spectrometer, as a pilot run of J-PARC E05 experiment. The K- beam intensity at the primary proton beam power of 39 kW was typically 6 × 105/spill with 5.5-sec. beam cycle. The energy resolution was estimated from the peak observed in the p(K-,K+)Ξ- reaction from a 9.54- g/cm2 CH2 target. We took the data on the 12C(K-, K+)X reaction with a 9.4-g/cm2 C target for about 10 days. We have observed about 60k events of quasi-free Ξ- production, and several tens of events in the bound region. While the analysis is near the final stage, we can see clear enhancements in the bound region above a flat background. Fitting to the enhancements with a few models suggest that the binding energy of 12 Be would be larger than the previously estimated value of about 4.5 MeV.

• | Presentation)

• (Abstract |

  • J-PARC E07 is a unique experiment at J-PARC to investigate double strangeness nuclei with hybrid emulsion method. It was designed to obtain ten times more double strangeness nuclei than that obtained by previous experiments. Moreover, it aims the first measurement of X-ray from Ξ-atom by Germanium detector.

    Beam exposure of E07 and photographic development of emulsion sheets are successfully completed. Several double strangeness events are found through searching work. I will report the present status, analysis of detected events, and the prospect of the experiment.

• | Presentation)

• (Abstract |

  • Nuclear spectroscopy with heavy ion beams and fixed nuclear targets has recently become a powerful tool to study sub-atomic nuclei with strangeness. The first HypHI experiment at GSI has demonstrated the feasibility of the method by reconstructing invariant masses and decay vertexes with 6Li beams at 2 A GeV bombarding a graphite
    target, and formation and mesonic π- decay of light hypernuclei have been successfully observed. The results have revealed a significantly short lifetime of hypertriton. Furthermore, it has also revealed indications of signals in the d+π- and t+π- invariant  mass distributions, that may indicate a possibility of a weakly bound state with a lambda hyperon together with two neutrons. These subjects are recently under debate.

    The accuracy and the statistics of the developed method for the hypernuclear spectroscopy with heavy ion beams should yet be improved. The method also has to be further developed with different detection techniques and beams at higher energies. A new experimental project to study hypernuclei has been proposed at GSI, and it will introduce the WASA central detector, which is currently at COSY in Juelich and under transportation to GSI, for pion measurement combined with the high resolution fragment separator, FRS, for measuring decay residues. The project has been already approved and experiments with WASA+FRS will be performed in coming years. The project will be continued with the Super-FRS at FAIR. Another new development at higher energies is in progress for the future heavy ion accelerator facility in China, High Intensity heavy ion Accelerator Facility, HIAF. It will open a possibility to study double-strangeness hypernuclei with heavy ion beams and fixed targets. The HIAF will also enable hypernuclei spectroscopy with its fragment separator with a similar fashion of the experiment with WASA+FRS at GSI. These new projects at GSI/FAIR and HIAF will be discussed.

• | Presentation)

Lunch break - on your own

• (Abstract |

  • Non-central heavy-ion collisions have large ~105 ħ) angular momentum which may be transferred, in part, to the quark-gluon plasma through shear forces that generate a vortical substructure in the hydrodynamic flow field. The vortical nature of the system is expected to polarize emitted hadrons along the direction of system angular momentum. Λ and anti-Λ hyperons, which reveal their polarization through decay topology, should be polarized similarly. The vorticity of the fluid is an important parameter for the generation of a Chiral Vortical Effect (CVE).

    These same collisions are also characterized by dynamic magnetic fields with magnitude as large as 1014 Tesla. A splitting between Λ and anti-Λ polarization may signal a magnetic coupling and provide a quantitative estimate of the field strength at freeze out. Details of the magnetic field and its evolution are of particular interest to other novel phenomena, e.g. the Chiral Magnetic Effect (CME).

    The STAR Collaboration has made the first observation of global hyperon polarization in non-central Au+Au collisions at Beam Energy Scan energies. A magnetic splitting is hinted at, but the improved statistics and resolution achievable with future runs are required to make a definitive measurement of the magnetic field.

• | Presentation)

• (Abstract |

  • The high collision energies reached at the Large Hadron Collider (LHC) at CERN in proton-proton, proton-lead and, in particular, lead-lead collisions, lead to significant production rates of fragile objects, i.e. objects whose binding energies are small compared to the average kinetic energy of the particles produced in the system.

    Such objects are, for instance, light (anti-)nuclei and (anti-)hypernuclei.

    The most extreme example here is the hypertriton, a bound state of a proton, a neutron and a lambda, where the separation energy of the lambda is only around 130 keV. These states, from the anti-deuteron up to the anti-alpha nuclei, are nevertheless created and observed in heavy-ion collisions at the LHC.

    Their production yields can even be well described in a statistical-thermal model approach with only three parameters, namely chemical freeze-out temperature Tch, volume V and baryo-chemical potential μB. The latter is close to zero at LHC, which means the ratio of anti-baryons to baryons is close to unity and in continuation also anti- nuclei and nuclei of the same type are produced in equal amounts. Tch at the LHC is extracted to be 156 MeV, which is a factor 1000 above the binding energy of the lambda to the deuteron, inside the hypertriton. The fact that the production of hadrons and also the (anti-)nuclei yields is well described in the thermal model approach can be understood by an isentropic expansion of the created fireball.

    In addition, the thermal model can be used to make predictions for the production of other fragile objects, such as bound states of hyperons and nucleons, or hyperon-hyperon bound states. The data collected at LHC can be used to test the existence of these bound states.

• | Presentation)

• (Abstract |

  • “K-pp” is the most essential system of kaonic nuclei that are expected to have several exotic natures, such as formation of dense state, due to the strong KN attraction [1]. Many researchers have eagerly investigated this system from both theoretical and experimental sides for a long time, expecting that the K-pp might give some hints to reveal detailed nature of kaonic nuclei.

    In theoretical sides, indeed, since the K-pp is just a three-body system, it has been investigated with various methods. As a result, we have reached a consensus that the K- pp should exist between KNN and πΣN thresholds as a resonant state, but that its binding energy still depends on the KN potential employed in models [2]. In the experimental side, J-PARC E15 group has conducted a K-pp quasi-bound state search experiment. They are going to report the result of their second-run experiment with high statics [3], and the Λp invariant-mass spectrum shows a clear signal between KNN and πΣN thresholds.

    Under such a current situation, we have developed a novel method, “Fully coupled- channel complex scaling method (Full ccCSM)”, to deal with the K-pp system as accurately as possible [4]. In the theoretical viewpoint, the K-pp is considered to be a coupled-channel system of KNN, πΣN and πΛN. In addition, as described above it should be a resonant state. We consider that coupled-channel aspect and resonance aspect are important in the theoretical study of K-pp. The full ccCSM can handle both aspects correctly, and additionally it provides us with a wave function to analyze the nature of the K-pp system. Therefore, we expect that the full ccCSM is the most suitable method to investigate the K-pp.

    With the full ccCSM, we have investigated the K-pp system, using a KN potential which is based on the chiral-SU(3) theory [5], since anti-kaon and pion are Nambu-Goldstone bosons and they are governed by the chiral dynamics. We will report the result of our self-consistent calculation in which we take into account the energy dependence involved in such a chiral SU(3)-based KN potential. If possible, we will show the result obtained in a semi-relativistic framework that should be better for light mesons.

• | Presentation)

Coffee break

Thursday, June 28, 2018

Parallel Sessions - 8:15 - 10:35

• (Abstract |

  • Building a comprehensive picture of the strong interaction is the goal of modern nuclear physics. While considerable progress has been made in the understanding of the nucleonnucleon (NN) interaction, we are still far from a complete understanding of the hyperonnucleon (YN) interaction, which plays a key role in hypernuclear matter and neutron stars. For the YN potential, some parameters can be obtained from the NN potential by using SU(3) symmetry. However, other parameters cannot be obtained from the NN potential due to broken SU(3) and must be obtained from fits to experimental data. One can access the dynamics of the YN interaction by studying nuclear reactions in which hyperons are produced. In this work, we determine the beam spin asymmetry, Σ, the hyperon recoil polarization, P_y, the polarization transfers to the Λ, O_x and O_z, from linearly polarized photons, and the polarization transfers to the Λ, C_x and C_z, from circularly polarized photons, for final-state interactions (FSI) in the reaction γd → K⁺Λn using data taken with the CLAS detector at the Jefferson laboratory. The FSI results are the first ever obtained for these observables and will be used to constrain the theoretical free parameters of the models of the YN potential. This work has been funded in part by the U.S. NSF under grant PHY- 1505615.

• | Presentation)

• (Abstract |

  • The BGO-OD experiment at the ELSA accelerator facility uses an energy tagged bremstrahlung photon beam to investigate the internal structure of the nucleon. The setup consists of a highly segmented BGO calorimeter surrounding the target, with a particle tracking magnetic spectrometer at forward angles.

    BGO-OD is ideal for investigating low momentum transfer processes due to the acceptance and high momentum resolution at forward angles. In particular, this enables the investigation of strangeness photoproduction where t-channel exchange mechanisms play a dominant role. As part of an extensive strangeness photoproduction experimental programme, the differential cross section measurements for K⁺Λand K⁺Σ⁰ photoproduction at centre of mass polar angles between 4 to 25 degrees will be presented.

    These first data at extremely forward angles are important for partial wave analyses, and models where accurate knowledge of t-channel mechanisms are required. The data also constrain models for hypernuclei electroproduction, where at very low Q², the K⁺Λ cross section is comparable to photoproduction.

    Preliminary differential cross sections, and recoiling baryon asymmetries will be shown. Opportunities to constrain the Y-N interaction using deuterium target data which is anticipated this year will also be presented.

• | Presentation)

• (Abstract |

  • Decay processes of Lambda hypernuclei up to p-shell have been measured with many experiments such as the bubble-chambers, the emulsions, and the missing mass spectroscopies. Theoretical calculations are good agreements with these experimental results especially for the mesonic weak decay (MWD) processes, in which a hypernucleus decays emitting with a pion. Decay processes of s-shell hypernuclei are dominated with the well-understanding MWD processes because the final states are not forbidden by the Pauli principle. Decay width would be estimated well in our frameworks.

    However, recent results of hypertriton reported by heavy-ion experiments have a surprise because their results are consistently supported more than 20% shorter lifetime than Lambda’s lifetime. That is unexpected result, furthermore, this short lifetime is difficult to reproduce in any theoretical frameworks. In order to settle this “puzzle”, some experimental projects were launched.

    We started a new project to study the decay processes of Lambda hypernuclei with the photon beam at ELPH Tohoku. We aim to produce the hypertriton with the (γ, K⁺) reaction from a ³He target. One of our advantages is better S/N ratio of the hypertriton because the hypertriton would be identified with missing mass technique. In addition, our approach is a different method to obtain the lifetime, namely, the lifetime would be deduced with direct timing measurement. New tagging photon beams are available with the energy range of 0.8-1.26 GeV, which is suitable energy for hypernuclear production. Momenta of K⁺ would be measured by Neutral Kaon Spectrometer 2 (NKS2), which has large solid angles. The decay timing would be measured with newly developed hightiming- resolution counters (TDL) that have 50 ps time-resolution.

    I will introduce our new project and expected results with detail simulation. Status of detector preparations is also shown in this presentation.

• | Presentation)

• (Abstract |

  • The associated strangeness production in pp interactions has been studied with the COSY-TOF detector in the reaction pp → pK+Λ close to threshold at the COSY accelerator at the research center Juelich in Germany. The underlying reaction mechanisms are not fully understood since perturbative QCD calculations cannot be applied at this energy regime. What has been determined so far is a strong influence of N* resonances in the reaction, a strong pΛ final state interaction and a NΣ – pΛ channel coupling which leads to an cusp effect in the pΛ invariant mass spectrum.

    The latest measurements at COSY-TOF have been carried out with a polarized proton beam. This allows also the determination of polarization observables such as the spin transfer of the beam to the $\Lambda$ or the beam analyzing power measured with the final state particles. These polarization observables could improve the understanding of the reaction mechanism further. Furthermore, the pΛ final state interaction is used to extract information about the bare pΛ interaction. It is possible to determine modelindependently the spin triplet scattering length utilizing the analyzing power from the Kaon asymmetry.

    In the HYP2015 conference in Sendai, Japan preliminary results on the scattering length and the various polarization observables were presented. In my talk I will show the final, published results and give a discussion about the statistical and systematic errors and a comparison with existing data.

• | Presentation)

Coffee break

• (Abstract |

  • We construct a new equation of state (EOS) for dense nuclear matter including Λ hyperons at zero and finite temperatures. At zero temperature, we calculate the energy per baryon of hyperonic nuclear matter by using the cluster variational method based on the realistic Hamiltonian composed of the Argonne v18 two-nucleon potential, Urbana IX three-nucleon potential, and the ΛN and ΛΛ potentials that are determined so as to reproduce the experimental data on single- and double-Λ hypernuclei [1, 2].At finite temperature, we extend the variational method proposed by Schmidt and Pandharipande to obtain the free energy per baryon for hyperonic nuclear matter. The obtained free energies and related thermodynamic quantities for various densities, temperatures, and particle fractions are reasonable.

    As an application of the obtained EOS, we investigate the composition of hyperon-mixed stellar matter under an appropriate equilibrium condition. The results show that the Λ hyperon mixing is enhanced when hyperon-mixed stellar matter becomes hotter and more neutron-rich. It is also found that trapped neutrinos in the stellar core increase proton fraction, and correspondingly Λ mixing is reduced in the high-density stellar matter.

    The goal of our project is to tabulate the resulting EOS in a wide range of densities, temperatures, and proton fractions for the use of core-collapse simulations, as an extension of the EOS table of normal nuclear matter we have constructed recently [3]. We will also report possible new results of our project.

• | Presentation)

• (Abstract |

  • In this talk we review some of the effects of hyperons on the properties of neutron and proto-neutron stars with an emphasis on the so-called "hyperon puzzle'', i.e., the problem of the strong softening of the equation of state, and the consequent reduction of the maximum mass, induced by the presence of hyperons, a problem which has become more intringuing and difficult to solve due the recent measurements of ~2M¤ millisecond pulsars. We discuss some of the solutions proposed to tackle this problem. We also reexamine the role of hyperons on the cooling properties of newly born neutron stars and on the development of the so-called r-mode instability.

• | Presentation)

• (Abstract |

  • We present an effective field theory (EFT) at leading order to describe light singleΛ hypernuclei [1]. Owing to the weak Λ binding and to the Λ-n short interaction range, meson exchange forces are approximated by contact interactions within a pion-less EFT where the only degrees of freedom are baryons. At leading order the theory contains both 2-body (singlet and triplet) and three 3-body interactions, a total of 5 terms associated with 5 coupling strengths or low energy constants (LECs). We adjust the 2-body LECs from available data that constrain the Λ-n scattering lengths. Because of the limited 3- body data, both 3-body and 4-body hypernuclear binding energies and excitation energies are used to adjust the 3-body LECs. To calculate the binding energies for the A-body systems with A>2, we have expanded the wave-function using a Gaussian basis. The stochastic variational method was employed to select the non-linear parameters. The resulting EFT is then applied to calculate the $\Lambda$ binding energy in ⁵_ΛHe, where the adjusted 3-body interactions largely resolve the known overbinding problem of ⁵_ΛHe[2].

• | Presentation)

• (Abstract |

  • The plausible explanation of the !(1405) resonance as a molecular state arising from coupled channel meson-baryon re-scattering in the strangeness S = -1 sector employing the lowest order chiral Lagrangian is one of the most important successes of Unitaritzed Chiral Perturbation Theory (UChPT). Despite this theoretical breakthrough, the aim for more precise calculations led the community to extend this approach with the inclusion of higher order terms and to explore higher energies. Unfortunately, the parameters of these higher-order terms are not fixed by the symmetries of the underlying theory, thus making the experimental fitting procedures to play a key role. In our previous studies [1,2], the relevance of the next-to-leading order (NLO) terms as well as the Born terms of the Chiral SU(3) Lagrangian for the K" channels was proved establishing the experimental K-p ! K" cross-section data as a very important ingredient to obtain more reliable values of the NLO parameters. The analysis of the isospin components of the K- p ! K" cross-section for different parametrizations in [2] revealed the need to explore reactions acting as isospin selectors. Motivated by the previous findings, we present results of a new fit which includes additional experimental data from the reactions K-p ! #! (I=0), #$0 (I=1) [3] and analyse their effect on the NLO parameters. In addition, we give predictions for other isospin filtering processes whose measurement would provide valuable constraints on the chiral models, namely, the K0!p \to K+"0 reaction, which is an I=1 filtering process and is planned to be measured at JLab, and the weak !b decay into a J/% and the I=0 component of a S = -1 meson-baryon [4]. The stability and the accuracy of all the parameters involved in the model have been examined by means of the explicit inclusion of !(1890), $(2030) and $(2250) resonances into the channels estimated to be sensitive to the NLO terms.

• | Presentation)

Parallel Sessions - 10:35 - 13:45

• (Abstract |

  • Double-Λ hypernuclei have been investigated for more than half a century, and several double hypernuclei have been found in nuclear emulsion. While they were produced by Ξ capture in light nuclei, Kumagai-Fuse and Akaishi proposed a possibility to produce a double-Λ hypernucleus as a decay product of a Ξ hypernucleus [1]. According to their calculation, the branching ratio of ⁷_ΞH to ⁵_ΛΛH+2n is as large as 90%, because many-body decay such as ⁴_ΛH+Λ+2n is disfavored due to its small Q-value. The existence of the ⁷_ΞH bound state is predicted in a more recent calculation [2].

    In this contribution, we will discuss a possible experiment for ⁵_ΛΛH production using the ⁷Li(K^-, K⁺)⁷_ΞH reaction, followed by the ⁷_ΞH to ⁵_ΛΛH+2n decay. A simultaneous study of Ξ hypernuclei and Double-Λ hypernuclei will give an insight into Ξ-ΛΛmixing and conversion, which is one of the most important features in the S=-2 sector.

• | Presentation)

• (Abstract |

  • The recent observation of 2-solar-mass neutron-stars rules out most of the current models for the hyperonic matter equation of state which favour the appearance of hyperons in the neutron star interior but predict maximum masses (M_max) incompatible with present data.

    This problem, known as the hyperon-puzzle, is presently a subject of very active research. A solution to it necessarily requires a better knowledge of the nuclear interaction involving hyperons. Due to the short lifetime of hyperons, the information provided by the available scattering data in the hyperon-nucleon (YN) sector is scarce, and does not allow the determination of the YN interaction using the same scheme successfully employed in the nucleon-nucleon (NN) sector.

    In the absence of scattering data, alternative information on the YN interaction can be obtained from hypernuclear physics. Hypernuclear spectroscopy appears to be the only practical way to study baryonic forces, and may play a significant role towards the solution of the so-called hyperon puzzle.

    Precise hypernuclear spectroscopy on medium to heavy hypernuclei with electron beams, which is only possible with the CEBAF electron beam, is critically important to obtain new information needed to constrain theoretical models of neutron star matter.

    The measured charge density distribution of ²⁰⁸Pb [1] clearly shows that the region of nearly constant density accounts for a very large fraction (~70 %) of the nuclear volume, thus suggesting that its properties largely reflect those of uniform nuclear matter in the neutron star interior. The validity of this conjecture has been long established by a comparison between the results of theoretical calculations and the data extracted from the ²⁰⁸Pb(e,e´p)²⁰⁷Tl cross sections measured at NIKHEF in the 1980s [2,3].

    The energy dependence of the spectroscopic factors, obtained from the analysis of the measured missing energy spectra, turns out to be in remarkably good agreement with the results reported in the pioneering work of Ref. [4].

    Microscopic calculations of the Λ spectral function in a variety of nuclei, ranging from ⁵He to ²⁰⁸Pb, have been recently carried out [5]. The results of this analysis—based on a realistic hyperonnucleon potential model constrained by the available scattering data—suggest that hyperon dynamics in ²⁰⁸Pb may be somewhat different compared to lighter nuclei, as signaled by a larger quenching of the spectroscopic factors.

    In view of its important astrophysical implications, the extension of the (e,e´K+) experimental program of Jefferson Lab to a heavy nuclear target with a large neutron excess, such as ²⁰⁸Pb, is of primary importance. The study of the ²⁰⁸Pb(e,e'K+)²⁰⁸TiΛ reaction will provide information on the properties of a bound hyperon in an environment little affected by surface and shell effects. It is complementary to the measurements that will be performed using ⁴⁰Ca and ⁴⁸Ca targets, whose main purpose is the analysis of the isospin dependence of hyperon dynamics.

    A proposal for studying the 208Pb(e,e'K+)208TiΛ reaction at Jefferson Lab Hall A is going to be submitted to the next Jefferson Lab PAC.

• | Presentation)

• (Abstract |

  • Recent experiments have presented more accurate data on the ΛΛ-binding energies of a few ΛΛ- hypernuclei. This is important as the ΛΛ- bond energies (ΔBΛΛ) of double-Λ hypernuclei provide a measure of the in-medium strength of the ΛΛinteraction. A mass formula, optimized with the newly available ΛΛ binding energy data, is used to estimate the binding energy and bond energy over a wide range of hypernuclei. The ΔBΛΛ values calculated with this mass formula are in good agreement with the experimental data, predictions of the quark mean-field (QMF) model and the relativistic mean-field (RMF) model as well. The ΛΛ-bond energy is found to diminish with neutron numbers, approaching zero near the neutron-drip line. In this formalism, the calculated binding energy difference in mirror nuclei arises from the Coulomb contributions and can be utilized to extract the Coulomb-corrected charge symmetry breaking effect. Our calculations show the regions where more data are needed for light hypernuclei.

• | Presentation)

Lunch break - on your own

• (Abstract |

  • Motivated by a renewed interest of hypernucleus studies, strangeness degree of freedom was implemented in the intranuclear cascade model INCL.

    INCL takes care of the first stage of reactions between a nucleon (or a light cluster) and a nucleus at energies from a few tens of MeV up to a few GeV. After emission of fast particles, a hot remnant nucleus is produced and then another model, combined to INCL, treats its de-excitation (the Abla model in our case). INCL was known as a reliable model in the non-strange sector for energies up to 2-3 GeV [1] and, after 2010 with implementation of the multiple pion emission, up to ~15 GeV [2,3]. Since at those energies other particles can play a (smaller) role, on the one hand, and, on the other hand, new experiments on hypernuclei in several facilities are in progress or planned, K's, Λ's and Σ's have been added as participant particles in INCL. Most important reactions involving these particles are also included. Concerning hypernucleus production, the de-excitation code Abla was also upgraded with evaporation of Λ's and fission of hypernuclei (hyper-fission).

    Main ingredients will be discussed and results compared to experimental data will be shown. Kaon spectra obtained from experiments with several targets and at different energies show good agreements most of the time. Role of the Delta-induced Kaon production will be discussed and other specific channels mentioned. Much less data exist on Lambda spectra, however data from the HADES collaboration were used and here also the results are very encouraging, especially compared to other models. The main remaining discrepancy was analysed and will be explained. Finally, hypernucleus production rates will be compared to the very rare existing data. In addition, we put constraints on the Lambda-nucleus potential by combining those experimental data to our calculation results.

• | Presentation)

• (Abstract |

  • In this presentation, I will review recent progress in theoretical studies about mesons containing strange and charm quarks in nuclear matter, especially focusing on the relation between the modification of meson spectra and QCD condensates. The question of what observables of meson spectra can be related to the partial restoration of chiral symmetry in nuclear matter, will also be addressed. I will furthermore discuss the potential relevance of these results for future experiments at J-PARC, FAIR and NICA.

• | Presentation)

• (Abstract |

  • The effective chiral theory allows to describe the nucleon-nucleon interactions, or other Hadron interactions, by using intermediate particles, the mesons, at low energies. The most frequent case is the pion exchange of protons and neutrons. Such models describe the internal nucleus interactions and some properties. The study of self-interactions, or uctuations, explains some internal properties, such as the difference u 􀀀  d and xS 􀀀 x  S. The present paper uses the ChEFT to estimate the total amount of strange quarks, in the proton and in the neutron. Due to the small mass difference involved, mainly among the kaons and hyperons envolved, it is obtained an asymmetry in these quantities.

    Till now, the contribution of strange quarks is below the error bar, therefore some other effects of the proposed difference must be studied. In some nuclei with relevant differences in proton and neutron numbers, the studied asymmetry may have some in uence in properties. Also, the deep inelastic scattering of protons and nucleon will result in different kaons production.

    Therefore, the strange asymmetry between proton and neutron is an interesting issue, and some additional works may be developed, such as the study of q2 dependence, or even improvements in the present calculations.

• | Presentation)

Lunch break - on your own

Parallel Sessions - 13:45 - 16:05

• (Abstract |

  • We present our recent results of baryon interactions with strangeness S=-1 based on Nambu-Bethe-Salpeter (NBS) correlation functions calculated from lattice QCD with almost physical quark masses corresponding to (mπ, mK) ≈ (146, 525) MeV and large volume (La)4 = (96a)4 ≈ (8.1 fm)4. In order to perform a comprehensive study of baryon interactions [1], a large number of NBS correlation functions from NN to ΞΞ are calculated simultaneously by using large-scale computer resources. In this contribution, we focus on the strangeness S=-1 channels [2] of the hyperon interactions by means of HAL QCD method. The latest results will be presented.

• | Presentation)

• (Abstract |

  • We report on our recent analysis of kaonic atom data [1] and consequent self-consistent calculations of K- nuclear quasi-bound states in nuclear many-body systems [2,3]. The single-nucleon K- optical potential developed within several chiral meson-baryon coupled-channel interaction models [4-7] was supplemented by a phenomenological potential representing K- multinucleon interactions. The multinucleon potential was fitted to kaonic atom data for each chiral K-N amplitude model separately and the total K- potential was further confronted with branching ratios of K- absorption at rest [1]. We demonstrate that the K- multinucleon absorption gives rise to substantial increase of the widths of K- nuclear states. The only two models [4,5] acceptable by the analysis [1] yield widths considerably larger than the corresponding K- binding energies. Identification of such states in experiment seems thus highly unlikely.

• | Presentation)

• (Abstract |

  • Using dispersion theory, we calculate the electromagnetic form factors for the transition of a Σ to a Λ hyperon at low energy. In this approach, the imaginary part of the form factors is written as a direct product of the two-pion-Sigma-Lambda amplitudes and the complex conjugate of the pion form factor. The two-pion-Sigma-Lambda amplitudes is also computed through a procedure combining dispersion theory and (NLO) chiral perturbation theory including a two pion re-scattering contribution. It is found that the inclusion of decuplet baryons in the intermediate state of the transition is necessary in order to obtain reasonable results, consistent with overall expectations. The electric transition form factor calculated through this method remains very small while the magnetic form factor obtained depends strongly on a not well-defined low-energy constant of the NLO Lagrangian. The predictive power of this approach will be enhanced by significantly constraining this constant from a measurement of the magnetic transition radius, a measurement that can be performed at the future Facility for Antiproton and Ion Research (FAIR).

• | Presentation)

• (Abstract |

  • The nuclear three-body systems AAB having two identical particles are studied based on the configuration space Faddeev equations. The three-nucleon systems and the kaonic NNK clusters are considered. For these systems, we propose two models related to isospin formalism. The first one is based on traditional isospin model and the second one is based on isospin given charge formalism. The relation between the models is defined by unitary transformation for corresponding isospin bases. The results of calculations for bound and scattering states, performed within the AAA and AAB representation for three-nucleon systems, are presented. The charge symmetry breaking effect is described within framework of AAB model with s-wave potentials. Analogically, we discuss the isospin formalism, the given charge formalism and the particle representation for NNK systems. In particular, we show that the coupling [1] between ppK- and pnK0 is artificial within the given charge formalism. The charge related basis elements, defined as (++-) and (+-+), correspond to the channels ppK- and pnK in Ref. [1]. These elements are two basis elements of the isospin basis defined within the given charge formalism. The full basis includes the third element, (-++). Each element is related to another by the cyclic permutation. Unitary transformation of the basis is eliminated this coupling. The isospinaveraged model [2] is discussed with relation to an isospin-less approach.

    This work is supported by the NSF grant HRD-1345219.

• | Presentation)

Coffee break

• (Abstract |

  • Recent Lattice QCD predictions for the mass of H-dibaryon pointing to the mass region near ΛΛ and Ξ-p thresholds encourage experimental searches. A dedicated experiment (JPARC E42) is designed to measure Λpπ-, ΛΛ and Ξ-p decays from the H-dibaryon in the 12C(K-,K+) reaction at the K1.8 beam line of J-PARC. A new superconducting Hyperon Spectrometer is now under commissioning, consisting of a conduction-cooled superconducting dipole magnet and a time projection chamber (HypTPC). This talk will review our new attempt to find evidence supporting the existence of the H-dibaryon in the wide mass range as well as the current status of the Hyperon Spectrometer.

• | Presentation)

• (Abstract |

  • In recent years the method of decay-pion spectroscopy was pioneered at the Mainz Microtron (MAMI). This method has the potential to achieve ground state mass measurements of light hypernuclei with unprecedented precision. Ongoing activities and future projects for the determination of masses of several light hypernuclei, in particular of the hypertriton, will be presented. We are aiming at statistical and systematic uncertainties of about 20 keV each. The hypertriton provides several important benchmarks for the strong interaction theory dealing with strange baryons, comparable to the role of deuterium for conventional baryon interactions.

    The present systematic uncertainty of these mass measurements is approximately 80 keV. The largest systematic error originates from the uncertainty in the MAMI beam energy affecting the absolute momentum calibration of the spectrometers by Δp ±100 keV/c, the sum of all other systematic errors contributes one order of magnitude less. In order to reduce this uncertainty, a novel high precision beam energy measurement based on undulator radiation was developed. The method takes advantage of the interference pattern produced by the two spatially separated undulators driven by the relativistic electrons. A high resolving monochromator was used to analyze the spectrum of the light. A preliminary pilot experiment proved the principle. However, systematic effects coming from calibration limitations and beam instabilities have to be considered and minimized.

    A successful experiment in 2018 has demonstrated the potential of such a new high precision beam energy measurement. A hypernuclear physics campaign with a lithium target is foreseen in the future. It will be complemented by extensive calibration measurements.

• | Presentation)

• (Abstract |

  • We have measured an inclusive missing-mass spectrum of the 12C(K-, p) reaction at the kaon incident momentum of 1.8 GeV/c at J-PARC K1.8 beam line. This measurement was carried out as a by-product of a pilot run of the J-PARC E05 experiment, which searched for the Ξ-hypernuclei via the 12C (K-, K+) reaction. We have compared the observed missing-mass spectrum with a DWIA calculation to study the Knucleus interaction. In this comparison, we have changed the depth of both real and imaginary part of the optical potential between K and nucleus. It is found that the observed spectrum is well reproduced by the calculation of the potential depth of V0 ~ - 100 MeV (real part) and W0 ~ -40 MeV (imaginary part). On the other hand, we have observed the definitive excess in the deeply bound region BK > 100 MeV, which cannot be explained by the any optical potential. This excess can be interpreted as a deeply bound Λ(1405) nucleus. In this talk, we will report the detail analysis results of this measurement.

• | Presentation)

• (Abstract |

  • Content The NΩ state with JP = 2+ and I = 1/2 are interesting candidates among the exotic hardons [1]. Unlike the deuteron, the NΩ state can be a compact six-quark state. Several attempts have been made to estimate the binding energy of the NΩ state in
    different quantum chromodynamics motivated models and they predict a bound state for the NΩ. The two-particle correlation function study allows one to extract final state interaction parameters. This method has been already used in experiments to study final state interactions between different particle species, like antiproton-antiproton and Λ-Λ. The two-particle correlation function of the proton-Ω is sensitive to the presence of the bound state [2] and can serve as a good observable to look for the NΩ signal in the
    heavy-ion collisions. We will discuss new STAR measurement of the two-particle correlation function for the proton-Ω from Au+Au collision at √sNN = 200 GeV.

• | Presentation)

Parallel Sessions - 16:05 - 18:35

• (Abstract |

  • The study of hypernuclei in deep-inelastic relativistic collisions of ion and other particle with nuclei open new opportunities for nuclear/particle physics and astrophysics. We review the main processes leading to the production of hypernuclei in these reactions: These are the disintegration of large excited hyper-residues (target- and projectile-like remnants with captured hyperons), and the coalescence of hyperons with other baryons into light clusters. We use the transport, coalescence and statistical models to describe the whole process, and demonstrate the advantages over the traditional hypernuclear methods: A broad distribution of predicted hypernuclei in masses and isospin allows for investigating properties of exotic hypernuclei, as well as the hypermatter both at high and low temperatures. We point at the abundant production of multi-strange nuclei and new bound/unbound hypernuclear states. The realistic estimates of hypernuclei yields in various collisions are presented. Many processes well known in normal reactions, such as evaporation, fission, multifragmentation, and Fermi-break-up are generalized and calculated for the case of excited hypermatter. There is a saturation of the hypernuclei production at high energies, therefore, the optimal way to pursue this experimental research is to use the accelerator facilities of intermediate energies.

• | Presentation)

• (Abstract |
• | Presentation)

• (Abstract |

  • Hyperons can be used as a powerful diagnostic tool that sheds light on some of the most challenging questions in contemporary physics. One is how and why the strong force confines quarks and gluons into composite systems, e.g. protons. The central question is: What happens if we replace one of the light quarks in a proton, with a heavier quark? Electromagnetic form factors (EMFF’s) is currently the best way to study hyperon structure. In the time-like region, the EMFF’s can be complex with a relative phase. This phase polarises the final state even in the case of an unpolarised initial state. Hyperons have the advantage compared to protons that their polarisation is experimentally accessible by the angular distributions of their decay products. However, due to experimental challenges, the phase has not been measured until now. In this talk, I will outline how to measure the phase between the electric and the magnetic form factor and present the latest results from the BESIII experiment at the BEPC-II electron-positron collider in Beijing, China.

• | Presentation)

• (Abstract |

  • The structure of the Λ(1405) is an important and long-standing issue to understand the Knucleus interaction. The J-PARC E31 experiment has been performed to investigate the Λ(1405) spectrum shape. Because it is hard to form the Λ(1405) directly by a KN scattering in free space, the E31 uses the d(K-, n) reaction with the incident kaon momentum of 1 GeV/c. We will identify three final states - Σ-π+, Σ+π-, Σ0π0 - so that the isospin structure of hyperon resonance states produced can be decomposed. The first physics run of the E31 experiment was performed in 2016. To enhance the statistics of the data set, we have performed the second physics run in the beginning of 2018. During the second run of E31, around 3.9 × 1010 kaons impacted on the deuteron target.

    In this presentation, we will report the current status of analysis and latest results from E31 data.

• | Presentation)

• (Abstract |

  • Studying the strong interaction for meson-baryon with femtoscopy in pp collisions with ALICE

    Understanding the strong interaction between particles pairs is one of the most fundamental problems in nuclear physics, but the parameters of this interaction are wellknown only for a limited set of particle pairs due to the lack of experimental data. Thanks to the excellent tracking and particle identification capabilities over a broad momentum range of the ALICE detector, a variety of different measurements are possible, among them the femtoscopy study.

    Femtoscopy is a technique allowing measurements of the space-time characteristics of particle production using correlations arising from quantum statistics and final-state interactions. Traditionally it is utilized to measure the size of the QGP fireball created in relativistic heavy-ion collisions, but it can also probe the strong interaction for different meson and baryon pairs in different colliding systems.

    In this analysis, femtoscopic correlations of kaons and protons and their anti-particles have been studied for the first time in pp collisions at √s= 5 TeV, 7 TeV and 13 TeV. The preliminary results show the experimental correlation between kaons and protons at low relative momentum with unprecedented precision. The measured correlations are fitted with the parametrization obtained by the "Correlation Analysis Tool using the Schrödinger Equation (CATS)", which can implement different theoretical potentials. In this analysis two models have been tested, one that takes into account only the Coulomb potential and the other include also the strong potential implemented in the Jülic model.

    The results indicate that present data are sensitive to the strong interaction, can be used to test further strong potentials and to extract the strong interaction parameters.

• | Presentation)

• (Abstract |

  • The Belle II experiment, now operating at the KEK laboratory in Japan, is a substantial upgrade of both the Belle detector and the KEKB e+ e- accelerator. It aims to collect 50 times more data than existing B-Factory samples. Belle II is uniquely capable to study the so-called "XYZ" particles: heavy exotic hadrons consisting of more than three quarks. First discovered by Belle, these now number in the dozens, and represent the emergence of a new category within quantum chromodynamics. This talk will present the capabilities of Belle II to explore both exotic and conventional quarkonium physics.

• | Presentation)

Friday, June 29, 2018

• (Abstract |

  • The ab initio description of nuclear structure and reactions has seen remarkable progress over the past decade, driven by groundbreaking advances in nuclear many-body theory and the advent of two- and multi-nucleon interactions from chiral effective field theory. As a result, ab initio calculations are now possible for an unprecedented range of nuclei and observables.

    I will discuss the transfer of the most advanced nuclear structure tools to the ab initio description of hypernuclei. Starting from two- and three-baryon interactions from chiral effective field theory, we adopt the similarity renormalization group to pre-diagonalize the Hamiltonian and enhance the convergence of the subsequent many-body calculation. Using the no-core shell model we then compute ground and excited states and the full spectroscopy of single-strange hypernuclei throughout the p-shell. For all steps of the calculation explicit Λ and Σ hyperons are included with their physical masses and with the ΛΣ conversion terms of the hyperon-nucleon interaction. I will show that the ΛΣ conversion plays a crucial role in hypernuclear structure and has profound implications for the so-called hyperon puzzle in neutron-star physics. Furthermore, I will discuss first ab initio calculations for light neutron-rich hypernuclei out to the neutron dripline.

• | Presentation)

• (Abstract |

  • The appearance of strange baryons in the inner regions of a neutron star (NS), where the density can exceed several times the nuclear saturation density, is likely to happen due to energetic considerations. The onset of strange degrees of freedom is considered as an effective mechanism to soften the equation of state (EoS). This softening affects the entire structure of the star, reducing the pressure and, therefore, the maximum mass that the star can stably support.
    The observation of very massive NSs, however, seems to rule out soft EoS, apparently excluding the possibility of hyperon formation in the core of the star. This inconsistency, usually referred to as the hyperonpuzzle, is based on what we currently know about the interaction between strange particles and nucleons. The combination of a poor knowledge of hypernuclear interactions and the difficulty of obtaining clear astrophysical evidence of the presence of hyperons in NSs makes the solution of the hyperon puzzle an intriguing challenge.
    We give our contribution to the discussion by studying the general problem of the hyperon- nucleon interaction. We attack the issue by studying properties of hypernuclei using an accurate quantum Monte Carlo (QMC) technique. We show that many-body hypernuclear forces are fun- damental to properly reproduce the ground-state physics of light and medium-mass Λ hyper- nuclei [1,2]. However, the poor abundance of experimental data on strange nuclei leaves room for a good deal of indetermination in the construction of hypernuclear potentials.
    This lack of accuracy leads to uncertainties in the prediction of NS properties. We apply the same QMC algorithm and the same hypernuclear interactions to study an infinite system of neutrons and Λ particles, deriving NS observables [3]. We show that the appearance of hyper- ons in the inner core of NSs is strongly dependent on the details of the underlying many-body hypernuclear interactions. A detailed analysis of the Λ separation energy in medium-mass hyper- nuclei [4] indicates the possibility to investigate features of the hyperon-nucleon-nucleon force in the medium-mass region of the hypernuclear chart, where new spectroscopy experiments are currently planned at Jefferson Laboratory. These studies could potentially provide new hints to the solution of the hyperon puzzle.
    This work is supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, under the FRIB Theory Alliance Grant Contract No. DE-SC0013617 titled “FRIB Theory Center - A path for the science at FRIB”, and by the NUCLEI SciDAC program. Computational resources have been provided by the National Energy Research Scientific Computing Center (NERSC), which is supported by the U.S. Department of Energy, Office of Science, under contract DE-AC02-05CH11231.

• | Presentation)

• (Abstract |

  • Recent advances in experiments of the symmetry energy of nuclear matter and in neutron star observations yield important new insights on the equation of state of neutron matter at nuclear densities. In this regime the equation of state of neutron matter plays a critical role in determining the mass-radius relationship for neutron stars. We show how microscopic calculations of neutron matter, based on realistic two- and three-nucleon forces that reproduce very accurately properties of light nuclei, make clear predictions for the relation between the isospin-asymmetry energy of nuclear matter and its density dependence, and the mass and radius for a neutron star.

    On the other side, several microscopic calculations suggested that the inclusion of hyperons softens the equation of state such that the corresponding maximum mass of neutron stars is much lower that astrophysical observations. This fact is particularly evident in non-relativistic calculations. We show that small changes in the nucleon- nucleon-Λ interactions have a dramatic role to the equation of state, while Λ binding energies in hypernuclei are qualitatively insensitive to the same adjustments. These results suggest that current experimental constraints are perhaps not sufficient to find a solution to the so called 'hyperon puzzle'.

• | Presentation)

Coffee break

• (Abstract |

  • In the last decade several targetted, well focussed experiments provided a remarkable amount of high quality information about s-, p- and, very recently, sd-shell Λ-hypernuclei. Their results contribute to significantly im- prove our knowledge of the field. However, some “surprising” outcomes came from non-dedicated large apparatus like STAR and ALICE, originally in- tended for heavy ion physics. In addition to the discovery of the 3 H, they found that the lifetime (τ ) of the 3 H (and of the 3 H), though affected by Λ Λ large errors, is remarkably lower than the lifetime of the free Λ hyperon, in contrast to the commonly accepted predictions.

    The precise determination of the τ (3 H) is a crucial point and it deserves a dedicated experiment. For this reason it is being proposed to study for the first time the (π−,K0) reaction on a liquid 3He target. The most suitable location for this measurement is the new K1.1 pion beam line, currently in an advanced commissioning stage at the Hadron Experimental Facility of J-PARC.

    For once, it will be possible to collect a large data sample in order to directly measure lifetimes with a very good precision ( 10%), by exploiting the delayed time spectrum method. The present apparatus design foresees the mechanical integration of some new detectors with the existing SKS complex, recently moved and installed in the K1.1 experimental area. Actually, in order to detect and to identify the products of the asymmetric K0 decay a suitably layered range detector should be installed upstream the magnetic spectrometer. The same detector will select with good energy resolution the π− from the mesonic decay of the 3 H.

    In addition, thanks to the apparatus modular concept, it will be possible to replace the whole liquid 3He target system with liquid 4He or with a series of solid targets, machined in thin tiles and arranged along the π− beam axis like a Venetian blind. This way it will be possible to perform a series of systematic measurements of the lifetime for several neutron-rich Λ-hypernuclei belonging to the p-shell. A very strong variation of the Γπ− value for isobars in the p-shell was predicted as due to shell-structure effects. Such measurements are easier than the one with the 3He target and they could serve as general test of the reliability of the method, in particular the performance of the spectroscopy through the (π−,K0) reaction. At the same time, such an arrangement will permit to simultaneously extract their partial weak decay widths Γπ− , Γp and Γπ0 .

• | Presentation)

• (Abstract |

  • By embedding mesons into nuclei and studying the property change of those particles in nuclear media, one can access the physics at densities beyond standard nuclear density, e.g., in neutron star matter, as well as the origin of matter (hadron) mass, in which the standard scenario is that the hadron masses are generated by the spontaneous chiral symmetry breaking of the vacuum. In this context, one of the most interesting meson is the anti-kaon (K) in the second-lightest K-meson group having the strange (s)-quark as a constituent quark, namely K􀀀 and K0.

    The confirmation of strong attraction of the KN interaction in the I = 0 channel 1,2) opens up very curious question. The KN attraction is so strong that it is more natural to form a bound state between a kaon and proton. In fact, there is a well-known resonance called (1405), the mass of which is located just below the mass threshold of the kaon and proton, M(K􀀀p); the resonance is assumed to be an exited state of a member of the  hyperon, i:e:; it is an excited uds-quark baryon system. Thus, it is very natural to ask whether (1405) can be interpreted as a bound state of a kaon and proton due to the strong interaction, i:e:; (1405) = \K􀀀p": If this is true, then the kaon can form a variety of nuclear bound states together with various nuclear systems. The strong KN attractive interaction might help form a high-density nuclear object beyond the standard nuclear density spontaneously. It might also help the study of the in-medium property change of mesons in nuclei.

    Therefore, a variety of experimental studies have been conducted by a number of experimental groups to identify the simplest kaonic nuclear bound state, \K􀀀pp."

    We employed unique approach utilizing kaon beam available at J-PARC. We bombarded a K􀀀 beam on a 3He target to knockout a neutron from the target nucleus at 1 GeV/c (p sKN
     1.8 GeV/c2), i:e:; K􀀀 +3 He ! K􀀀 ps ps + n (ps denotes spectator proton). The cross section of this reaction is rather high, because of the presence of the Y  resonance near
    1.8 GeV/c2, which decays strongly to KN. There are several key advantages in this reaction channel to search for the kaonic bound state. First, the recoil kaon momentum (or momentum transfer), qK, is as small as 200 MeV/c ( pF ) in this reaction; therefore, one can expect very efficient nuclear formation as K􀀀 ps ps ! \K􀀀pp:" Another advantage is that the presence and the commitment of K􀀀 in this channel is secured from the beginning. Still another advantage is that the two- (or multi-) nucleon absorption reaction can be expected to have a small cross section. Finally, we can cover the target region with a cylindrical detector system (CDS) to identify the final state of \K􀀀pp" with sensitivity to the decay process. We also placed large-volume neutron counter arrays in the forward direction 15 m away from the target system to identify neutrons in the production channel with a high missing-mass resolution of about 10 MeV/c2.

    The pilot run of J-PARC E15 showed quite remarkable results. The semi-inclusive forward neutron spectrum shows a large yield below the mass threshold of M(K􀀀pp) as a long tail from the quasi-elastic kaon scattering, implying the existence of strong KN attractive interaction.3) An even more impressive spectrum was obtained in the p invariant mass spectrum of the p n final state, in which we observed an event concentration near the M(K􀀀pp) threshold, and the centroid of the event concentration is well within the bound region.4)

    Thus, we conducted a new beam time for further study, especially focusing on the p n final state. We have very positive and confirmative data for the existence of the structure observed in the pilot run, as described in several conferences. We are still analyzing our data in detail, to check our analysis integrity from various aspects. In the conference, we will report most updated result.

• | Presentation)

• (Abstract |

  • The AMADEUS collaboration is performing experimental investigations in the low energy strangeness QCD sector. The K- nuclear absorption processes on light nuclear targets are studied, taking advantage of the monochromatic low-momentum negatively charged kaons produced by the DAΦNE collider and exploiting the KLOE detector as an active target. The K− single and multi-nuclear absorptions on H, 4He, 9Be and 12C, both at-rest and in-flight (for a kaon momentum of 100 MeV/c), are investigated with the aim to determine the nature of the controversial Λ(1405), the non-resonant hyperon pion formation amplitude below the K¯N threshold, the yields and cross sections of K− multi-nucleon absorptions (intimately related to the antikaon multi-nucleon clusters properties) and the K− scattering cross sections on light nuclear targets.

• | Presentation)

Lunch break - on your own

• (Abstract |

  • The Hyperon-Nucleon (Y-N) interactions play an important role in understanding the strong interaction. It is suggested that alternative Y-N couplings can be a possible solution to the recent observations of neutron star exceeding two solar masses, the socalled hyperon puzzle. A precise measurement on masses and lifetimes of hypertriton and anti-hypertriton can enrich our knowledge on Y-N interactions.

    In this talk, we will present the first precise measurement of hypertriton and antihypertriton masses in heavy-ion collisions at STAR with the Heavy Flavor Tracker (HFT). Hypertritons and anti-hypertritons are reconstructed through both two-body decay channel (³He + π^-) and three-body decay channel (p+d+π^-) using the high-statistics data collected in 2014 and 2016 Au+Au collisions at √s_{_NN} = 200 GeV. The measured masses will be used to extract the binding energies for hypertriton and anti-hypertriton. We will also report an improved measurement of the hypertriton and anti-hypertriton lifetimes. Physics implications on the understanding of Y-N interactions via our measurements will be discussed.

• | Presentation)

• (Abstract |

  • I will review the present knowledge on charmed hypernuclei, charmed mesic nuclei and heavy quarkonia binding in nuclear matter. I will summarize the main theoretical approaches and present recent theoretical predictions and relate them to upcoming experiments in different laboratories.

• | Presentation)

• (Abstract |

  • As the lightest charm and beauty baryon, respectively, the Λc and Λb are the major decay products of baryons with open or hidden heavy flavors. Various Λc and Λb production processes may provide valuable information on the heavy baryon spectroscopy including penta-quark states with hidden charm and beauty. The baryon spectroscopy with open heavy flavor may play a unique role for understanding light diquark correlation. On the other hand, the decay of Λc and Λb may produce various lighter baryon resonances including hyperon resonances, penta-quark states with hidden charm and strangeness, etc.. Interesting physics and prospects on hadron spectroscopy from the production and decay of Λc and Λb will be reviewed.

• | Presentation)

Coffee break