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


At large momentum transfer the valence quark components of the nucleon are ... New technology approach and results. Target: Hybrid pumping approach K- Rb- He ... – PowerPoint PPT presentation

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

GEn at High momentum transferHall A experiment
- E02-013
Hall A collaboration meeting, June 22rd, 2006
Bogdan Wojtsekhowski,also for G.Cates and
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,
    ... )

  • 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
  • Milestones of data analysis
  • Perspectives for even higher momentum transfer
    with the same detector package
  • 30 s

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

Expectation for accuracy of the result
  • 30 sec

One photon approximation
Nucleon vertex
Sachs form factors
Cross Section
Motivation - GPDs
Motivation - Neutron Electric Form Factor
Motivation - Neutron Electric Form Factor and
its importance for GPDs
Experimental approach Beam / Target Asymmetry
  • Experiments either
  • measure both components (by rotating target
  • or
  • rely on polarimetry

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

Asymmetry vs P_miss - FSI effectsas from 2002
This type plot we need to get ASAP from GEN data
JLab Hall A During E02-013
Hall A E02-013 3D View
Hall A Neutron Detector (BigHAND)
Hall A with BigBite
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
  • Precision field direction - air supported compass
  • Beam line elements air cooling jets,
    non-conductive W collimators, He bags, Be/Al
  • Beam line/cell alignment
  • Beam line local shielding
  • AAA
  • AAA
  • AAB
  • AAA
  • AAA
  • AAA
  • AAB
  • AAB
  • ABC
  • ABC

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

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

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

  • 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
  • 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.
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