GEn at High momentum transfer Hall A experiment - E02-013

1
GEn at High momentum transferHall A experiment
- E02-013
Hall A collaboration meeting, June 22rd, 2006
Bogdan Wojtsekhowski,also for G.Cates and
N.Liyanage
2
Students, experts, run coordinators and shift
takers (gt3 shifts)

• S. Abramyan, B. Craver, A. Kellerher, A.
  Kolarkar, J. Miller, S. Riordan
• J.P. Chen, R. Michaels , E. Chudakov, A.
  Shahinyan , D. W. Higinbotham, J. Singh,
• Al Tobias, S. Wood, V. Nelyubin, S. Tajima, A.
  Camsonne, N. Gevorgyan
• B. Sawatzky, M. Jones, R. Feuerbach, N.
  Liyanage, D. Day, T. Holstrom,
• Ole Hansen, T. Averett, R. Holmes
• V. Punjabi, O. Rondon, G. Urciuoli, K. Allada,
  B. Anderson, A. Beck, S. Beck,
• B. Crowe, F. Cusanno, C. Dutta, S. Fuchs, K.
  Grimm, D. Howell, Joe Katich, B. Moffit,
• C. Perdrisat, D. Protopopescu, A. Puckett, Xin
  Qian, Yi Qiang, P. Reimer, D. Rohe,
• A. Saha, J. Wright, X. Zhu, J. Arrington, S.
  Frullani, L. Kaufman, J. Lopez,
• D. Margaziotis, F. Wesselmann, H. Yao,
  C.Fernandez, R. Lindgren, M. Khandaker,
• W. Korsch, W. Boeglin, L. Coman, O. Glamazdin,
  J. Kelly, P. Markowitz, L. Pentchev,
• S. Stepanyan, V. Sulkosky, A. Acha, K. Aniol, J.
  Annand, C. Ferdi, L. Fraile,
• F. Garibaldi, X. Jiang, J. LeRose, B. Quinn, S.
  Sirca, Tim Ngo, Eli Piasetzky,
• G. Rosner, J. Udias, R. Ransome, Ron Gilman.

• an important list of experts, who design
  and built GEN systems (UVA, YerPhI, BINP, ITEP,
  ... )

3
Outline

• Motivation of the experiment or Why high momentum
  transfer measurement of GEn is so much needed?
• The results of 75 days of running 2/25-5/10
• comissioning development statistics
  collection
• Milestones of data analysis
• Perspectives for even higher momentum transfer
  with the same detector package

• 30 s

4
Motivation - Form factors

• Form factors (FFs) are functions in a hadron
  current operator
• In one photon approximation scattering cross
  section is factorisable and FFs could be
  calculated (first Born approximation)
• At low momentum transfer in first BA FFs are
  related to the classical charge and
  magnetic distributions of the nucleon
• At intermediate momentum transfer the FFs deal
  with a convolution of the hadronic
  structure of the photon (Vector Mesons) and the
  nucleon structure (including the pion cloud)
  
• At large momentum transfer the valence quark
  components of the nucleon are providing a
  dominant contribution into FFs
  
• Asymptotic properties of the FFs are predicted in
  the pQCD limit
• Connections to Deep Inelastic electron
  Scattering, VDCS, and RCS were discovered
  recently in the GPD formalism

• 30 sec

5
Expectation for accuracy of the result

• 30 sec

6
One photon approximation
Nucleon vertex
Sachs form factors
Cross Section
7
Motivation - GPDs
8
Motivation - Neutron Electric Form Factor
9
Motivation - Neutron Electric Form Factor and
its importance for GPDs
10
Experimental approach Beam / Target Asymmetry
Asymmetry

• Experiments either
• measure both components (by rotating target
  spin)
• or
• rely on polarimetry

11
Main difficulties and our solutions

• 3He target allows for of 10 times higher
  luminosity than polarized ND3 target
• Nuclear effects in 3He target unfavor at Q2 lt 1
  GeV2, at the Q2 value of our interest 3He target
  is a way to go!
• Need also 10 times larger acceptance of the
  electron detector --gt BigBite! Is 1 resolution
  enough? Is it possible to run at 105
  higher luminosity than it used at NIKHEF ?
  

• Number of events L W e sM/(Q2)4, so we
  need 100 times higher L W e than it was
  obtained in best prev. experiment
  Q2 1 GeV2
  
  
  
• Quasi elastic scattering vs inelastic channels
  (pion,two pions, delta..) for 2.5 GeV/c neutron
  1-b 0.07. Achievable resolution is of 0.008.
  

• Cut on Ptransv,recoil selects QES, it is possible
  because of quite good angular resolution of the
  neutron detector!
• Cut on Plong,recoil is modest just /-250 MeV/c

12
Asymmetry vs P_miss - FSI effectsas from 2002
proposal
This type plot we need to get ASAP from GEN data
13
JLab Hall A During E02-013
BigHand
BigBite
14
Hall A E02-013 3D View
15
Hall A Neutron Detector (BigHAND)
16
Hall A with BigBite
17
New technology approach and results

• Target
• Hybrid pumping approach K-gt Rb-gt He
• Fiber optics lines for laser light with optimized
  optics for multi-fiber source
• High temperature ceramic oven
• 8 hours spinup time, 55 polarization with
  8 mkA beam
• NMR in both pumping/target chambers
• Holding field with skinny dipole magnet iron
  box
• Precision field direction - air supported compass
  
• Beam line elements air cooling jets,
  non-conductive W collimators, He bags, Be/Al
  windows
• Beam line/cell alignment
• Beam line local shielding

• AAA
• AAA
• AAB
• AAA
• AAA
• AAA
• AAB
• AAB
• ABC
• ABC

18
New technology approach and results

• Electron Arm
• Wire chamber type, constr. quality
• Front end electronics
• Shielding, W blocks, wood, ..
• Shower trigger
• Shower PID
• Timing plane
• HV system
• Gas system
• TDC (VME)
• TDC (FastBus)

• AAA
• AAA
• AAB
• AAA
• ABC
• AB
• AAA
• AAA
• DD
• AAA

19
New technology approach and results

• AAA
• AAB
• AAA
• AAB
• AAA
• AAB
• AAA
• AAA
• AAA

• Neutron arm
• Detector reliability - 99-99.9
• Front end electronics
• Trigger
• HV system
• Mechanical system/shielding (1-3 hours)
• TDC F1
• TDC FastBus
• ADC FastBues
• Cabling system

20
Analysis team and time line (goal)

• Six PhD students and one MD student with
  thesis projects, more plan
  join for learning opportunity
  
• Robert is leading GEN analyzer and analysis with
  help from Ole
• Spokespeople and students advisers (Averett,
  Egiyan,Franklin, Kelly, Korsch, Liyanage)
  
  
  
  
• Preliminary results for 1.8 GeV2 kinematics by
  October 2006
• Final analysis of all four kinematics is a
  requirement for every PhD from this
  experiment, expected before end of 2007

21
Summary

• Ideas in GEN proposal about operation of the open
  detectors at luminosity of the polarized target
  are working. Hall A GEN has Figure-of-Merit by a
  factor of 100 higher than best of previous
  experiments with any polarized targets.
• The novel target concept and both arms detector
  equipment had operate with very good up time.
• Collaboration had succeed to be ready for
  experiment in time and collected very good data
  at four kinematics.
• We are sure that all effort (hope you agree)
  directed to GEN preparation pay back very
  efficiently for physics of the form factor and
  for at least of 100 PAC days already approved A
  rated experiments based on the BigBite
  spectrometer.
• Thanks collaborators and contributors for support
  of E02-013 and continuing efforts in analysis.
• Stay tune to learn about neutron shape during
  next year.
• Measurement at Q24.5 GeV2 could be done today
  with present setup.