Spectator Tagging Project

Overview

The Spectator Tagging Project develops the capabilities for high-energy electron scattering experiments with polarized light ions (deuteron 2H, 3He) and detection of spectator nucleons (protons, neutrons) at a future Electron-Ion Collider (EIC). Such experiments address basic questions of nuclear and strong interaction physics:

  • Deep-inelastic structure of the neutron and the nucleon spin decomposition
  • Modification of the free nucleon's quark and gluon densities in nuclei
  • Coherent nuclear phenomena in Quantum Chromodynamics

Polarized high-energy deuteron beams become available with the JLab medium-energy EIC design (MEIC). The detection of spectator protons ("tagging") identifies the active neutron and controls its quantum state during the scattering process, greatly improving the precision and control compared to conventional measurements. The MEIC forward detector provides the necessary coverage and resolution and is being optimized for the purpose. R&D objectives include:

  • Develop theoretical models for high-energy scattering on polarized light ions (2H, 3He) with spectator tagging at EIC energies
  • Develop event generators for Monte-Carlo simulations of inclusive, diffractive and exclusive final states
  • Simulate measurements with the MEIC beam and detector design and study rates, acceptance, and resolution
  • Analyze pseudodata and quantify physics output of measurements with spectator tagging

The project is carried out as a collaborative effort of theorists and experimentalists. It is supported by JLab's Laboratory-Directed Research and Development (LDRD) program as FY14/15 Project "Physics potential of polarized light ions with EIC@JLab." The resources developed (theoretical models, computer codes, event generators) are publicly available for scientific applications and further development. The project aims to enable collaboration with laboratory users and other interested scientists to explore the physics potential of a future EIC.

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Collaboration

JLab LDRD collaborators:

  • Doug Higinbotham (JLab Physics)
  • Wally Melnitchouk (JLab Theory)
  • Pawel Nadel-Turonski (JLab Physics)
  • Christian Weiss (Lead Scientist, JLab Theory)

External collaborators and users:

  • Wim Cosyn (Ghent University)
  • Vadim Guzey (Petersburg Nuclear Physics Institute)
  • Charles Hyde (Old Dominion University)
  • Sebastian Kuhn (Old Dominion University)
  • Kijun Park (Old Dominion University)
  • Misak Sargsian (Florida International University)
  • Mark Strikman (Penn State University)

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Resources

Resources developed in the project include physics models for high-energy scattering processes on light ions with spectator nucleon tagging, event generators for Monte-Carlo simulations, and analysis tools for pseudodata.

Physics models represent theoretical models of the differential cross sections for high-energy processes on light ions with spectator nucleon tagging and their implementation in computer codes. Implementations are presently available for the following channels:

  • Deuteron, unpolarized, inclusive scattering
  • Deuteron, unpolarized, diffractive final states
  • Deuteron, polarized, inclusive scattering
  • Helium-3, unpolarized, inclusive scattering

The theoretical treatment of nuclear effects (nuclear binding, final-state interactions, polarization, coherence at small x) varies widely between the different channels and is the subject of on-going development. Information on the presently available models (codes, documentation) and instructions for downloading can be found here.

Event generators provide random sets of kinematic variables of final-state particles (momentum 4-vectors) for Monte-Carlo integration and detector simulations (tracking). Generators for EIC kinematics are available in different formulations (reference frames) and several output formats. The codes and documentation are maintained on the JLab github server and can be obtained here.

The documents and computer codes posted here are the result of on-going scientific research and development. They are made available with the sole intent to stimulate scientific discussion, invite feedback, and enable further physics simulations for the EIC. Users are free to use and modify the codes for scientific purposes. Any scientific results obtained with the help of these resources should be properly acknowledged (please contact the authors for instructions). No guarantee is implied regarding the correctness of results or the performance of the codes.

Internal documents are maintained on the Spectator Tagging Wiki.

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Selected results

               

Fig. 1. Neutron structure from deep-inelastic scattering on the deuteron with spectator proton tagging. Left: (a) Conditional DIS on the deuteron e + De'+p+X. (b) Neutron pole at t = MN2 arising from the impulse approximation diagram. Right: Simulated measurement of the recoil momentum dependence with MEIC and on-shell extrapolation t → MN2 . The plot shows the conditional structure function, with the pole factor removed, as a function of the off-shellness MN2- t calculated from the measured proton recoil momentum. The error bars indicate the expected statistical errors. The three sets correspond to measurements in different intervals of the recoil light-cone momentum fraction αR. Figures from [arXiv:1409.5768].

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Publications

  • W. Cosyn, V. Guzey, M. Sargsian, M. Strikman, C. Weiss, Electron-deuteron DIS with spectator tagging at EIC: Development of theoretical framework, Proceedings of 6th International Conference on Physics Opportunities at an Electron-Ion Collider (POETIC6), Palaiseau, France, 7-11 September 2015, EPJ Web Conf. 112 (2016) 01022, arXiv:1601.06665 (INSPIRE)
  • C. Weiss, Electron-deuteron deep-inelastic scattering with spectator tagging at EIC. Technical summary; JLAB-THY-14-1997 [PDF]
  • W. Cosyn, V. Guzey, D.W. Higinbotham, C. Hyde, S. Kuhn, P. Nadel-Turonski, K. Park, M. Sargsian, M. Strikman, C. Weiss, Neutron spin structure with polarized deuterons and spectator proton tagging at EIC, Proceedings of Tensor Polarized Solid Target Workshop, Jefferson Lab, March 10-12, 2014; JLAB-THY-14-1955; arXiv:1409.5768 (INSPIRE)
  • V. Guzey, D. Higinbotham, Ch. Hyde, P. Nadel-Turonski, K. Park, M. Sargsian, M. Strikman, C. Weiss, Polarized light ions and spectator nucleon tagging at EIC, Proceedings of DIS 2014, XXII. International Workshop on Deep-Inelastic Scattering and Related Subjects, University of Warsaw, Poland, April 28 - May 2, 2014; JLAB-THY-14-1913; arXiv:1407.3236 (INSPIRE)

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Presentations

  • W. Cosyn, Deep-inelastic scattering on the polarized deuteron with spectator nucleon tagging, QCD-N'16 (4th Workshop on the QCD Structure of the Nucleon), Getxo, Spain, 11-15 July, 2016 (slides)
  • W. Cosyn, Tagged spectator DIS off a polarized spin-1 target, QCD Evolution 2016, NIKHEF, Amsterdam, Netherlands, 30 May - 3 June, 2016 (slides)
  • W. Cosyn, Tagged Spectator DIS off a polarized spin-1 target, DIS2016 (XXIII International Workshop on Deep-Inelastic Scattering and Related Subjects), DESY, Hamburg, Germany, 11-15 April, 2016 (slides)
  • W. Cosyn, Next generation nuclear DIS with spectator tagging at EIC, DIS2016 (XXIII International Workshop on Deep-Inelastic Scattering and Related Subjects), DESY, Hamburg, Germany, 11-15 April, 2016 (slides)
  • Ch. Hyde, Tagging with few-body nuclei, Electron Ion Collider User Group Meeting 2016, UC Berkeley, 6-9 January 2016 (conference webpage)
  • W. Cosyn, Tagged spectator DIS off the deuteron as a tool to extract neutron structure, Poster, 11th European Research Conference on Electromagnetic Interactions with Nucleons and Nuclei (EINN2015), Paphos, Cyprus, 1-5 November 2015 (conference webpage)
  • Ch. Hyde, Forward Tracking with the JLab/MEIC detector concept, 2015 Fall Meeting of the APS Division of Nuclear Physics, Santa Fe, NM, October 28-31, 2015 (abstract)
  • K. Park, A study of neutron structure with (un)polarized deuterons and spectator tagging at EIC, 2015 Fall Meeting of the APS Division of Nuclear Physics, Santa Fe, NM, October 28-31, 2015 (abstract)
  • D. Higinbotham, Opportunities with light ions at EIC, 2015 Fall Meeting of the APS Division of Nuclear Physics, Santa Fe, NM, October 28-31, 2015 (abstract)
  • C. Weiss, Spectator tagging and short-range correlations with an Electron-Ion Collider, EMMI Workshop “Cold dense nuclear matter: From short-range nuclear correlations to neutron stars”, GSI Darmstadt, Germany, October 13-15, 2015 (slides)
  • K. Park, Forward spectator tagging event generator, EIC Software Meeting, Jefferson Lab, September 24-25 (conference webpage)
  • C.Weiss, Simulating spectator tagging at EIC, EIC Software Meeting, Jefferson Lab, September 24-25 (conference webpage)
  • K. Park, A study of neutron structure with (un)polarized deuterons and forward spectator tagging at EIC, 6th International Conference on Physics Opportunities at an Electron-Ion Collider (POETIC 6), Ecole Polytechnique, Palaiseau, France, September 7-11, 2015 (slides)
  • C. Weiss, DIS on light nuclei with spectator tagging: New applications at intermediate and small x, 6th International Conference on Physics Opportunities at an Electron-Ion Collider (POETIC 6), Ecole Polytechnique, Palaiseau, France, September 7-11, 2015 (slides)
  • C. Weiss, MEIC polarized deuteron R&D, DOE Science and Technology Review, JLab, July 28-30, 2015 (slides)
  • C. Weiss, Nuclear DIS with spectator tagging at EIC, New Directions in Nuclear Deep Inelastic Scattering, ECT* Trento, June 8-12, 2015 (slides)
  • V. Guzey, Nuclear Shadowing in Tagged DIS on Deuteron, New Directions in Nuclear Deep Inelastic Scattering, ECT* Trento, June 8-12, 2015 (slides)
  • C. Weiss, High-Energy Nuclear Physics with Spectator Tagging. Old Dominion University, March 9-11, 2015 (conference webpage)
  • K. Park, Neutron Structure with Tagging at MEIC. High Energy Nuclear Physics With Spectator Tagging, Old Dominion University, March 9-11, 2015 (conference webpage)
  • K. Park, Neutron structure with (un)polarized deuterons and forward spectator tagging at the Electron-Ion Collider, APS April Meeting, Baltimore, MD, April 12, 2015 (abstract)
  • C. Weiss, Quark-Gluon Structure of Light Nuclei with Spectator Tagging at EIC, APS April Meeting, Baltimore, MD, April 12, 2015 (abstract)
  • W. Cosyn, Final state interactions in inclusive and semi-inclusive DIS, 4th International Workshop on Nucleon Structure at Large Bjorken x (HiX2014), Laboratori Nazionali di Frascati, Italy, 16 Nov - 21 Nov 2014 (conference webpage)
  • P. Nadel-Turonski, Physics at an electron-ion collider, 4th International Workshop on Nucleon Structure at Large Bjorken x (HiX2014), Laboratori Nazionali di Frascati, Italy, 16 Nov - 21 Nov 2014 (conference webpage)
  • C. Weiss, Next-Generation Nuclear DIS with EIC: Polarized Light Ions and Spectator Nucleon Tagging, QCD Town Meeting, Temple University, Philadelphia, September 13-15, 2014 (.pdf)
  • Ch. Hyde, Neutron Spin Structure via Spectator Tagging at the EIC, QCD Town Meeting, Temple University, Philadelphia, September 13-15, 2014 (.pdf)
  • C. Weiss, Nuclear structure with an Electron-Ion Collider, DNP Town Meeting on Nuclear Structure and Nuclear Astrophysics, Texas A&M University, August 21-23, 2014 (.pdf)
  • C. Weiss, Physics potential of polarized light ions with EIC@JLab, FY2015 LDRD proposal review, Jefferson Lab, July 15, 2014 (.pdf)
  • K. Park, Study of Neutron Structure via Far-Forward Tagging of eD → e'NX in EIC, 2014 EIC Users Group Meeting, Stony Brook University, 24-27 June, 2014 (.pdf)
  • C. Weiss, Neutron structure with spectator tagging at MEIC, 2014 JLab Users Group Meeting, JLab, 2-4 June, 2014 (.pdf)
  • C. Weiss, Light-front methods in next-generation nuclear physics at EIC, Light Cone 2014: Theory and Experiments for Hadrons on the Light Front, NC State University, Raleigh, NC, 28 May 2014 (.pdf)
  • V. Guzey, P. Nadel-Turonski, C. Weiss, Physics opportunities with tagged deep inelastic scattering on polarized light nuclei at EIC, XXII International Workshop on DIS and Related Subjects, Warsaw, Poland, May 1, 2014 (.pdf)
  • Kijun Park et al., Neutron structure via forward tagging of the eD -> e'NX reaction at the Electron-Ion Collider, APS April Meeting, Savannah, GA, April 5-8, 2014 (.pdf)
  • C. Weiss, Next-Generation Nuclear Physics with Forward Proton/Neutron Detection at MEIC, Accelerator Science and Technology for the Electron-Ion Collider (EIC14), JLab, March 17-21, 2014, JLAB-THY-14-1860 (.pdf)
  • C. Weiss, Polarized Deuterium Physics with EIC, Tensor Polarized Solid Target Workshop, JLab, March 10-12, 2014, JLAB-THY-14-1859 (.pdf)
  • C. Weiss, Physics potential of polarized light ions with EIC@JLab, FY2014 LDRD proposal review, JLab, July 15, 2013 (.pdf)

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Context and background

  • An Electron-Ion Collider (EIC) has been proposed as a next-generation facility for nuclear physics in the U.S. and worldwide. Specific designs are being developed at Brookhaven National Lab (BNL) and Jefferson Lab (JLab). Information on the EIC physics program can be found in:
    • A. Accardi et al., Electron Ion Collider: The Next QCD Frontier - Understanding the glue that binds us all, EIC White Paper, arXiv:1212.1701 (INSPIRE)
    • A. Accardi, V. Guzey, A. Prokudin, C. Weiss, Nuclear physics with a medium-energy Electron-Ion Collider, Eur.Phys.J. A48 (2012) 92, arXiv:1110.1031 (INSPIRE)
    • D. Boer et al., Gluons and the quark sea at high energies: Distributions, polarization, tomography, Report on 2010 BNL/INT/JLab program on the science case for an Electron-Ion Collider, arXiv:1108.1713 (INSPIRE)
  • The medium-energy EIC design (MEIC) developed by JLab collides electron and light ion beams at electron-nucleon squared center-of-mass energies in the range seN = 250-2500 GeV2 and luminosities up to 1034cm-2 s-1. It enables deuteron beam polarizaion by using an innovative figure-8 layout of the collider rings to compensate the effect of spin precession. Detailed information on the MEIC design can be found in:
    • S. Abeyratne et al., Science Requirements and Conceptual Design for a Polarized Medium Energy Electron-Ion Collider at Jefferson Lab, arXiv:1209.0757 (INSPIRE)
    • JLab MEIC Wiki Pages
  • Forward detection of protons, neutrons and nuclear fragments is an essential requirement for spectator tagging. The MEIC forward detector is integrated with the interaction region and provides excellent coverage and resolution. Protons and charged fragments passing through the final focusing quadrupole are analyzed with a magnetic dipole field and detected with longitudinal momentum resolution δ pL/pL ∼ 10-4, transverse momentum resolution δ pT 20 MeV, and complete coverage down to pT = 0. Forward neutron detection is possible with calorimeters, taking advantage of the finite crossing angle of the beams. Detailed information on the MEIC foward detector can be found on the Wiki Pages.
  • A fixed-target experiment at JLab has measured deuteron structure functions with spectator proton tagging at 6 GeV beam energy using the CLAS BoNuS detector, and will be extended to 11 GeV beam energy. See: S. Tkachenko et al., Measurement of the structure function of the nearly free neutron using spectator tagging in inelastic 2H(e, e'p)X scattering with CLAS, Phys.Rev. C89 (2014) 045206, arXiv:1402.2477 (INSPIRE)

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