Proposal Number:               P04-001                                Hall: C

 

Title:                          Measurement of F2 and R = sL/sT on Nuclear Targets in the Nucleon Resonance Region
 
 

 

 

Contact person:                 Arie Bodek (Rochester) and Thia Keppel (Hampton University)

 

 

Beam time request:

Days requested for approval:                            5 days

Tune up included in beam line request:               no

 

Beam characteristics:

Energy:                                                                         1.18,2.29,3.41,4.52,5.64 GeV

Current:                                                                        30 – 80  mA

Polarization:                                                      no

 

Targets:

Nuclei:                                                                          4 cm LH2,LD2, A1(MT),

C,Quartz,Si,Ca,Fe,Cu

Rastering:                                                         nominal

Polarized:                                                                     no

 

Spectrometers:

HMS:                                                                           single arm mode

SOS:                                                                            single arm mode

 

Special requirements/requests:    none

 

 

Technical Comments:

 

1) The experiment is technically doable, as proven by the previous E94-110 experiment, a similar measurement on the proton. In addition, experiment E99-118 has performed similar measurements on nuclear targets in the region of W2 ~ 5 GeV2, with far worse particle identification, charge symmetric background, and radiative correction problems.

 

2) The experiment is an add-on to approved experiment E02-109 that performs similar measurements on a deuterium (and Al dummy) target. No overhead, apart from target changes, is included in this experiment, as it is assumed that the additional targets can be added either to the cryogenic target ladder, or to a standalone nuclear target ladder.

 

 
 
 
3) If the experiment would be scheduled separately from E02-109, the overhead for this experiment would amount to an additional 5-6 days, not requested.

 

4) As this is an L/T separation, many beam pass changes are required, and an additional one (major) linac energy change. However, these energy changes are compatible with the previously approved E02-109.

 

5) The experiment assumes some unconventional targets such as Si, Ca, and Quartz. The choice of these targets is given in by targets/detectors used in neutrino physics experiments. The Ca target may be kept in oil as it reacts with air (such a target has been used before in Hall C).  The form of some of the non-standard targets is not specified. We assume that the Quartz target will be in powder form contained within thin windows since a solid Quartz target may fracture due to electric charging. The Silicon target also needs more thought.

 

6) The estimated uncertainty in D RA is not given, but is presumably similar as the estimate of D RD of E02-109: 0.03-0.05. To reach such precision in an experiment accessing a wide range of rates in the detectors is difficult, although conditions are easier than in E99-118.  The achieved uncertainty of E99-118 should be shown.

 

7) The experiment does include some overhead for investigation of charge symmetric backgrounds and radiative corrections.

 

8) Even though only 5 days are requested, the experiment may have a large radiation budget.   Up to 80 µA of beam will be used on targets as thick as 12% radiation length. Since the experimenters want to use the HMS as low as 11 degrees, it may not be possible to use the larger diameter downstream pipe.
 
9) It is not clear which solid target ladder the proponents plan to use. A lot of targets need to be accommodated. In addition, the power depositions can be quite high.  For example, at 80 µA, the power deposition in the 12% Carbon target is approximately 360 Watts.  E.g., the final current allowed by some of these pends strongly on the thermal contact with external active or passive cooling (as also mentioned in the proposal);

 

10) A corrected beam requirements list is needed.

 

 

Proposal Number:                  P04-003                                  Hall: C

 

Title:                                       The Neutron Electric Form Factor at Higher Q2 up to 4.0 (GeV/c)2 from the Reaction 2H(e,e’n)1H via Recoil Polarimetry

 

Contact person:                      Richard Madey (Kent State University & JLab)

 

Beam time request:

Days requested for approval:                            37 days

Tune up included in beam line request:               yes

 

Beam characteristics:

Energy:                                                                         3.68, 5.61 GeV

Current:                                                                        1-90 mA

Polarization:                                                      80%

 

Targets:

Nuclei:                                                                          15 cm LH2, LD2, Al(MT), Fe

Rastering:                                                         nominal

Polarized:                                                                     no

 

Spectrometers:

HMS:                                                                           yes

SOS:                                                                            no

 

Special requirements/requests:    This is a large installation experiment requiring the installation of a dedicated neutron polarimeter. 

 

 

Technical Comments:

 

1) This is a major installation experiment asking for a lot of floor time.  The installation time is estimated to be 2-3 months.  Teardown is estimated to be 1 month. 

 

2) The beam time request assumes 80% beam polarization.  If the more commonly achieved value of 75% is assumed, the beam request would increase by about 4 days.

 

3) The experimental technique is both feasible and elegant. Very few potential systematic problems in this experiment fail to cancel in the cross-ratio.  A reasonable estimate was made for Ay in this proposal. The method for making this estimate was checked against earlier E93-038 extractions of Ay and found to be in good agreement (Although Ay drops out in the ratio of asymmetries, it enters the counting statistical error as 1/Ay.)
 
4) The background simulations are some of the most thorough done for any JLab experiment. No surprises are expected. The collaboration has previously made test measurements of shielded scintillators which confirmed their GEANT simulations.

 

5) The names of collaboration members found on the proposal were taken from E93-038. This list should be updated to only include those who have agreed to participate.

 

6) Are the detectors and electronics used in E93-038 available for this new experiment?  Do the polarimeter and shadow shield support structures still exist?  Will they or their designs be suitable for this experiment, or is significant time and effort expected from the Hall C engineering and design staff?

 

7) The n-g tof difference is about 1/3 what it was in the old experiment.  Will the p0 peak in the D TOF spectra still be resolved?  In the 2.5m path length of the polarimeter, these tof differences will be sub-nanosecond in the new experiment.  The separation of n-p from n-C in the polarimeter will also worsen.  What consequences will this have on the measurement?  What consequences will the poorer neutron energy resolution have on the experiment? 

 

8) An experimental layout figure should be provided checking possible interference with G0 in its back-angle configuration and interference between the HMS and the shield house or shadow shield support structure.

 

9) The one day overhead request leaves less than one minute (48 seconds) on average for each target/magnet change or run start/stop.  Hence, the overhead is largely underestimated. 

 

10) Would the use of a sub-harmonic microstructure of the beam benefit these or higher Q2 measurements?

 

Proposal Number:                  P04-004                                  Hall: C

 

Title:                                       Search for Exotic Pentaquark q++, q*++ and q+ in Hall C

 

Contact person:                      Haiyan Gao (Duke University)

 

Beam time request:

Days requested for approval:                            18 days

Tune up included in beam line request:               no

 

Beam characteristics:

Energy:                                                                         3.17 GeV

Current:                                                                        8-30 mA

Polarization:                                                      no

 

Targets:

Nuclei:                                                                          4 cm LH2, LD2

Rastering:                                                         nominal

Polarized:                                                                     no

 

Spectrometers:

HMS:                                                                           no

SOS:                                                                            yes

 

Special requirements/requests:    This is a large installation experiment requiring the installation of the HKS and a neutron detector. 

 

 

Technical Comments:

 

1) The experiment cannot use the HKS set up without extensive modification.  There are two channels being studied: i) photoproduction off the proton that requires only K+K- detection, and ii) off the neutron that also requires neutron detection.
 
2) This is a major installation experiment which requires the HKS and beam splitter from the hypernuclear experiment, the SOS, the Bremsstrahlung radiator, a neutron detector, and a well-instrumented beam dump line.  The estimated installation time is three months. Teardown is one month.
 
3) This proposal requires that the SOS and HKS be placed close to the beam line.  Both spectrometers could have stray fields affecting the beam.  There is no mention how the 42 µA beam can still be properly dumped.
 
4) The HKS shielding hut is designed for far lower luminosities than assumed in this proposal. There would need to be GEANT simulations of this experiment, including the Bremsstrahlung radiator and the downstream spectrometer materials and beam dumpa line, to estimate the background rates in the HKS detectors.
 
5) With the neutron array moved out-of-plane in order to access smaller laboratory scattering angles, a large out-of-plane momentum mismatch with respect to the K+K- pair may be induced. If so, production rates will drop steeply since only the high momentum tail of the neutron Fermi distribution can contribute. This needs to be simulated.
 
6) The iterative procedure as described in the Simulations chapter could bias results.  It is a two body process on top of a 3 body background.  The photon energy must be reconstructed from both K+ and K-.
 
7) The proposal lacks discussion of the neutron detection for the q+ part of the experiment. Detecting neutrons with good time resolution and high efficiency in a high luminosity environment with an upstream 6% radiator will be difficult. No sweeping magnet or shielding is discussed, and there is little room for either one. The neutron bar energy threshold and efficiency are not specified. A neutron rate is presented in Table III but not explained.  Photon rates are not given.
 
8) The real to random rate for neutron detection is not given.

 

9) A precise definition of and specifications for the neutron detector are needed.

 

10) There are discrepancies between the beam requirement list and the proposal text, e.g. in beam current on the LH2 target.

 

 

 

 

Proposal Number:                  P04-008                                  Hall: C

 

Title:                                       Measurements of Target Single-Spin Asymmetry in Elastic ep scattering

 

Contact person:                      Xiaodong Jiang (Rutgers University)

 

Beam time request:

Days requested for approval:                            20 days

Tune up included in beam line request:               partial

 

Beam characteristics:

Energy:                                                                         4.8 GeV

Current:                                                                        50-100 nA

Polarization:                                                      no

 

Targets:

Nuclei:                                                                          H,14N,He,Al,Cu,C

Rastering:                                                         PT raster

Polarized:                                                                     yes

 

Spectrometers:

HMS:                                                                           yes

SOS:                                                                            no

 

Special requirements/requests:    This is a Large Installation experiment, requiring installation of a substantially modified polarized target, a new beam line chicane or beam dump, and several new calorimeter detectors

 

 

Technical Comments:

 

1) This experiment uses "new" detector systems consisting of calorimeters previously used in other halls at Jefferson Lab and Protvino, as well as a significantly modified polarized target system. The latter also mandates a new chicane, or a new beam dump. No specific design requirements are suggested for either of the latter, and there are no specifications given for the new dump requirements, although this is stated as the preferred option.

 

2) This is a large installation experiment. Installation time has not been included, and is estimated to be 3-4 months. Deinstallation is estimated to be 1-2 months.

 

3) Strong technical support is assumed from the JLab Target Group for the implementation, commissioning, installation, calibration, and operation of the modified polarized target. We do note that this may be alleviated somewhat by strong involvement on this proposal by the UVA group.

 

4) No single group responsibility is assigned to the Michigan magnet refurbishing (if necessary) and implementation.

 

5) A detailed qualification is needed of what is available, what will be new, and what work is needed for this target system.

 

6) The collaboration is proposing to use a conventional magnet in their polarized target system. What are the implications on target polarization and thus running time if a higher field superconducting magnet were to be used instead?

 

7) Electronics for the new detectors will be almost entirely in the Hall. Experience with this, and whether a shield house is needed, may come from the GEp-III E01-109 experiment. However, careful consideration of this issue should be given also to the detectors closer to the beamline.

 

8) Backgrounds are investigated for electron, positron, and photon rates for this experiment, while the comparable results shown from CLAS include electron-pion backgrounds.
 
9) Background estimates should incorporate general room background coming from the He bag and exit window, particularly for the 5 degree detectors.
 
10) As noted in the proposal, new power, control, and monitoring devices will be required for the 70 GHz microwaves.

 

11) The 5 and 10 degree detectors are stated as necessary for luminosity monitors. It is noted that the HMS will be used as such as well. It is not investigated whether the SOS could also be used.  Would it be possible to run the experiment using the spectrometer(s) alone as monitors with no small angle detectors?

 

12) It is noted that accurate beam charge monitoring is of use to the experiment, however no required accuracy is stated.

 

 
13) The small angle detectors won't have the advantage of simultaneous e+p and p+e measurements to check systematic uncertainties.

 

14) Infrequent reversals mean that normalized yields will be compared which are taken roughly 6 hours apart. A luminosity monitor is therefore needed with 0.1% stability over 6 hours. Larger drifts than this will significantly increase the random errors. It is not clear how to achieve this and the systematics were not discussed.

 

15) Relativistic proton detection in Lead glass is possible by Cerenkov light. However, it appears that dE/dx was simulated rather than "visible" energy from Cerenkov light. If true, there are implications for thresholds, efficiencies, background rates, and proton angle resolution.

 

16) As proposed, an energy calibration is needed i) for electron W reconstruction and ii) so that a threshold can be applied to define hit blocks. Will elastic scattering or some other reaction be used for energy calibrations?

 

17) The expected W resolution varies with kinematic setting but is very poor. Assuming an electron energy resolution of 5%/√(E'), and an electron angle resolution of roughly 0.6 degrees (limited by the projected target length), the expected resolution in W is nearly 200 MeV. This may be of some use in reducing backgrounds, but does not isolate the elastic electrons.

 

 

Proposal Number:                  P04-009                                  Hall: C

 

Title:                                       Measurement of the Born-Forbidden Recoil Proton Normal Polarization in Electron-Proton Elastic Scattering

 

Contact person:                      David Mack (JLab)

 

Beam time request:

Days requested for approval:                            27 days

Tune up included in beam line request:               no

 

Beam characteristics:

Energy:                                                                         0.57, 0.85, 1.0, 2.0, 3.0 GeV

Current:                                                                        75 mA

Polarization:                                                      75%

 

Targets:

Nuclei:                                                                          4 cm LH2, Al(MT)

Rastering:                                                         nominal

Polarized:                                                                     no

 

Spectrometers:

HMS:                                                                           yes

SOS:                                                                            no

 

Special requirements/requests:    This is a large installation experiment requiring the installation of a superconducting solenoid and new detector systems.

 

 

Technical Comments:

 

1) This is a major installation class experiment requiring the procurement, refurbishment and modification of a medium sized surplus superconducting solenoid magnet.  The magnet refurbishment needs to include a conversion from a persistent mode to a continuously powered mode of operation in order to allow for the required frequent changes in field strength.  There are two identical surplus solenoids available so confidence should be high that at least one can be made to operate as required for the experiment.  The experiment proposes a movable support structure which will travel on the SOS rails.  This approach is probably not cost effective for a single run experiment.  The collaboration might consider roller technology instead.  The experiment plans to employ the standard HMS setup as the electron arm.

 

2) The experiment requires 5 different energies (3 of these are at a fixed linac energy).  The lowest energy of 570 MeV may be invasive to experimental running in the other two Halls.

 

3) Setup time for checkout and Moeller measurements is not included and is estimated to be 1 day total.  Commissioning time for the new detector system is not included.

 

4) The cryo-target and beam current requirements are straightforward.  Specifically, a 4cm flask with 75 microamperes of normal microstructure polarized beam.

 

5) The most critical aspect for this experiment seems to lie in the feasibility of the proposed approach to control systematic errors via the periodic reversal of the field of the solenoid magnet used to process the spin of the scattered proton.  Previously groups have employed large solenoids to process the spin of neutrons. With neutrons this is straightforward in that the trajectories are not altered. In the case of polarized protons from a finite length target both the trajectory and spin direction will be altered. Although, the proposal asserts that the errors introduced by any trajectory alterations will be small and that the use of wire chambers after the solenoid should allow a precise calibration of such effects they present no detailed Monte-Carlo to back up the simple calculations given in the proposal. This is not to say they have made any mistakes, but rather that for an experiment of this precision a good Monte-Carlo is needed to quantity estimates of systematic errors.

 

6) It is unclear what the singles rate on the wire chambers will be from high energy gammas that penetrate the thin Pb (x-ray) shield: since they have a direct view of a high luminosity LH2 target at ~30 degrees in the lab.  The air + wire chambers have a low conversion efficiency for gammas, but they also have relatively long deadtimes with respect to the detectors used in the polarimeter.

 

 

Proposal Number:                  P04-013                                  Hall: C

 

Title:                                       Measurement of the Nuclear Dependence of the EMC Effect at Large x

 

Contact person:                      David Gaskell (JLab)

 

Beam time request:

Days requested for approval:                            8 days

Tune up included in beam line request:               yes

 

Beam characteristics:

Energy:                                                                         6.0 GeV

Current:                                                                        20 - 80 mA

Polarization:                                                      no

 

Targets:

Nuclei:                                                                          4 cm LH2, LD2, Al(MT), 7 Li 9Be, 12C,27Al, 40Ca, Cu, Ag,Au

Rastering:                                                         nominal

Polarized:                                                                     no

 

Spectrometers:

HMS:                                                                           single arm mode

SOS:                                                                            single arm mode

 

Special requirements/requests:    7Li target on cryo ladder.

 

 

Technical Comments:

 

1) Based on previous experience (E89-009 and E99-118) this experiment is certainly doable. Both the pion background and the charge symmetric background estimates seem reasonable and will be measured.  The time allocated for these background measurements seems to be sufficient. Also, enough time has been allocated for checkout and calibration.

 

2) The estimated systematic uncertainties for the point-to-point systematics are small but seem to be on the conservative side. The scale uncertainties are dominated by the acceptance difference between the 4cm liquid targets and the thin nuclear targets and by the nuclear target densities and are significantly larger than the proposed statistical uncertainties. As the nuclear target density uncertainty is estimated to vary between 0.5 and 2% it would be interesting to see it separately for the various nuclear targets.  On the same subject, it is not entirely clear if the measurement on 7Li (using a much different beam current and thus subject to additional systematics) is really worth the time allocated for it.

 

3) There are lots of solid targets, two of which require special handling: Li and Ca both oxidize slowly in air at room temperature, and oxidize rapidly in water while releasing Hydrogen. In the case of Li, enough heat can be generated to ignite the Hydrogen. The amount of material is small, but special procedure will be needed. For example, the Lithium target can be stored under oil and safely transferred to the scattering chamber at the start of the experiment. However, without a load-lock system, if the scattering chamber were to be opened after the experiment, moisture could condense on the cool Lithium target and start a small self-sustaining fire. Such fires can only be put out with special classes of fire extinguishers. Fortunately, the total amount of Li can be less than 1 gram if the target is well-designed. The laboratory can work with the experimenters to handle the Li target safely, but the physics benefit should outweigh the cost.

 

4) The experiment does not seem particularly sensitive to the beam energy and may still comfortably be run at lower energies.

 

5) The collaboration should consider including additional measurements on hydrogen.  The quality of the existing data in the DIS region at very high x certainly could be greatly improved.

 

6) It is not clear what target ladder the proposal requires.  There is enough space on the cryo target and solid target ladder combined, but the cryo target ladder does not allow for rotation.

 

 

Proposal Number:                  P04-014                                  Hall: C

 

Title:                                       Measurement of GEp/GMp using elastic polarized p(e,e’)p up to Q2=3.50 (GeV/c)2

 

Contact person:                      Xiaochao Zheng (Argonne National Lab)

 

Beam time request:

Days requested for approval:                            17 days

Tune up included in beam line request:               yes

 

Beam characteristics:

Energy:                                                                         3.6, 6 GeV

Current:                                                                        85-200 nA

Polarization:                                                      80%

 

Targets:

Nuclei:                                                                          NH3

Rastering:                                                         PT raster

Polarized:                                                                     yes

 

Spectrometers:

HMS:                                                                           yes

SOS:                                                                            no

 

Special requirements/requests:    This is a Large Installation experiment, requiring installation of the Polarized Target and Beam Line Chicane

 

 

Technical Comments:

 

1) This is a large installation experiment, albeit a standard one requiring the polarized target and associated beam line chicane.  Installation time has not been included, and is estimated to be 2-3 months.  Teardown is estimated to be one month.

 

2) The beam time request assumes 80% beam polarization.  If the more commonly achieved value of 75% is assumed, the beam request would increase by about 2 days.

 

3) Strong technical support is assumed from the JLab Target Group for the installation, calibration, and operation of the polarized target.  We do note that this may be alleviated by the strong involvement on this proposal by the UVa group.

 

4) The experiment will require a low current dump in the Hall for the non-parallel field measurements.  This technique has before been used for the E93-026 experiment.

 

5) There is no basis for the claimed 0.3 mrad absolute angle accuracy of the HMS (with the polarized target field in place), but a larger value of 1 mrad does not significantly affect the error budget.

 

6) No details were given of how the target spin direction was previously determined to 0.1 degrees, and whether this was with respect to an unspecified laboratory coordinate system or with respect to the q-vector for central HMS kinematics. If this value were several times larger, it would become one of the larger systematic errors.

 

7) Careful alignment of the target will be needed to get the beam through the target without clipping the coils.

 

8) The approved E01-109 GEp-III experiment already provides a sensitive test to systematic uncertainties due to spin precession in the Hall A apparatus.  Does this experiment bring more to this problem?

 

 

Proposal Number:                  P04-019                                  Hall: C

 

Title:                                       Measurement of the Two-Photon Exchange Contribution in ep Elastic Scattering Using Recoil Polarization

 

Contact person:                      Riad Suleiman (MIT)

 

Beam time request:

Days requested for approval:                            25 days

Tune up included in beam line request:               no

 

Beam characteristics:

Energy:                                                                         2.26, 2.84, 3.77, 4.70 GeV

Current:                                                                        75 mA

Polarization:                                                      80%

 

Targets:

Nuclei:                                                                          4 cm LH2

Rastering:                                                         nominal

Polarized:                                                                     no

 

Spectrometers:

HMS:                                                                           yes

SOS:                                                                            no

 

Special requirements/requests:    This is a large installation experiment requiring the installation of the large electron calorimeter currently constructed for the E01-109 GEp-III experiment in Hall C.

 

Technical Comments:

 

1) The beam time request assumes 80% beam polarization.  If the more commonly achieved value of 75% is assumed, the beam request would increase by about 2 days.

 

2) Although the proposal asks for specific energies, there appears from kinematics to be some flexibility.
 
3) The beam time request assumes that the experiment can be scheduled to run right after  experiment E01-109, the Gep-III experiment.  If this is not possible, additional time will be required, both for installation and checkout and calibration of the BigCal.  No estimate of the extra time needed in this scenario is given.

 

4) No information on background rates has been provided, of special relevance for an open geometry detector at realtively small angles and large luminosity.

 

5) The experiment relies on use of the BigCal to “reduce background by ensuring the exclusivity of the reaction”.  No quantitative statement is made regarding either what level of background reduction is necessary, or what level can be achieved by using BigCal in coincidence with the HMS.

 

6) There is no discussion about backgrounds from the target cell walls.  Given the rather small magnitude of Py, this could be important.

 

7) One planned method of testing the false asymmetries in the recoil polarimeter relies on using the exclusive H(e,e’p+) process.  It is not clear that the BigCal+HMS combination will have the missing-mass resolution to cleanly identify this process.  Is the method valid if one includes backgrounds from associated Delta production and/or semi-inclusive production?  Could p+’s from exclusive r production be a background?

 

 

Proposal Number:                  P04-020                                  Hall: C

 

Title:                                       A measurement of two-photon effects in unpolarized electron-proton scattering

 

Contact person:                      John Arrington (Argonne National Lab)

 

Beam time request:

Days requested for approval:                            9 days

Tune up included in beam line request:               yes

 

Beam characteristics:

Energy:                                                                         1.1, 2.2, 3.3, 4.4, 5.5 GeV

Current:                                                                        35-70 mA

Polarization:                                                      no

 

Targets:

Nuclei:                                                                          4 cm LH2, Al(MT)

Rastering:                                                         nominal

Polarized:                                                                     no

 

Spectrometers:

HMS:                                                                           single arm mode

SOS:                                                                            single arm mode

 

Special requirements/requests:    Energies chosen compatible with Hall A E02-010 experiment. 

 

 

Technical Comments:

 

1) Precise choice of beam energies requested in this proposal is not clear.  The beam requirements list indicates 5 energies, but the kinematics described in the text and figures of the proposal reflect far more energies, consistent with E02-010.  A table with exact beam energy request is needed.
 
2) To control the luminosity at 70 µA, the intrinsic beam spot size should be made approximately the same size at each new energy. One needs to quantify the energy-to-energy luminosity changes to better than ±0.5%.

 

3) Current understanding of the electronic dead time is inconsistent with the 0.1% uncertainty requirement.  The proponents should assist in tracking down these problems before the experiment if they wish to control the dead time error at the 0.1% level.

 

4) It would be nice to see predicted elastic signal and backgrounds assuming HMS resolutions. Although tracking in the HMS may have smaller non-Gaussian tails, the resolution is worse than an HRS.

 

5) Precision measurements may have to deal with frequent beam trips. Fortunately, data analysis can now be gated off if the beam current drops below some threshold. However, when the current is again above threshold, the experimenters should make sure the cryotarget has stabilized.