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Nucleon Transversity at 11 GeV Using a Polarized 3He Target and

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									The Study of Neutron Transversity from a
  Polarized 3He Target at 12 GeV JLab
                 (


A Workshop on Hadron Physics in China and Opportunities
                  with 12 GeV JLab
              July 31- August 1, 2009
           Lanzhou University, Lanzhou, China


                     Haiyan Gao (高海燕)
                     Duke University/TUNL
                      Durham, NC, U.S.A.
                Outline
• Introduction
• First experiment at 6 GeV
   (Y. Qiang) J.P. Chen
• Transversity with 12 GeV at JLab
• Summary
        QCD                                       Nucleon Structure
•   Strong interaction, running coupling ~1
    -- QCD: the theory of strong interaction
    -- asymptotic freedom (2004 Nobel)
        perturbation calculation works at
        high energy
    -- interaction significant at
      intermediate energy                      • Charge and magnetism
                                                 (current) distribution E
        quark-gluon correlations
                                                   – Nucleon: Electric GE
    -- confinement                                   and magnetic GM form
                                                     factor
        interaction strong at low energy       • Spin distribution
        coherent hadron                        • Quark momentum and
                                                 flavor distribution
    -- Chiral symmetry                         • Polarizabilities
                                               • Strangeness content
    -- theoretical tools:
                                               • …..
      pQCD, OPE, Lattice QCD, ChPT
       Leading-Twist Quark Distributions
              ( Eight parton distributions functions)
      non-
   vanishing
  integrating
      over K 


  Transversity:

                                             K - dependent,
K - dependent,                                   T-even
     T-odd
                       Transversity
• Three twist-2 quark distributions:
   – Momentum distributions: q(x,Q2) = q↑(x) + q↓(x)
   – Longitudinal spin distributions: Δq(x,Q2) = q↑(x) - q↓(x)
   – Transversity distributions: δq(x,Q2) = q┴(x) - q┬(x)
• Some characteristics of transversity:
   – δq(x) = Δq(x) for non-relativistic quarks
   – δq and gluons do not mix → Q2-evolution simpler
   – Chiral-odd → not accessible in inclusive DIS
• Rapidly developing field, worldwide efforts: BNL, Belle at KEK, CERN,
  DESY, JLab, FAIR project at GSI, …

• It takes two chiral-odd objects to measure transversity
            Access Parton Distributions through Semi-
                          Inclusive DIS
                              d             2   y2
                                                        
                        dxdydS dzdh dP  xyQ 2(1   )
                                        h
                                         2      2


                       {FUU ,T  ...
                                           cos(2h )
                                                                          Unpolarized
Boer-Mulder              cos(2h )  F  UU            ...
                        S L [ sin(2h )  FUL 2h )  ...]
                                              sin(


Transversity            ST [ sin(h  S )  FUT h S )
                                                 sin(
                                                                          Polarized
   Sivers               sin(h  S )  ( FUL h S )  ...)
                                             sin(                         Target

Pretzelosity             sin(3h  S )  FUT 3h S )  ...]
                                              sin(


                        S L e [ 1   2  FLL  ...]                        Polarized
                                                                              Beam and
                                                         cos(h S )
                        ST e [ 1   cos(h  S )  FLT
                                      2
                                                                       ...]} Target

                SL, ST: Target Polarization; e: Beam Polarization
   Separation of Collins, Sivers and pretzelocity effects
              through angular dependence


                 1 N  N
AUT (h , S ) 
        l   l

                 P N  N
 AUT sin(h  S )  AUT s sin(h  S )
    Collins              Siver


 AUT
   Pretzelosity
                sin(3h  S )


  AUT llins  sin(h  S )
   Co
                                 UT
                                       h1  H1
  AUT  sin(h  S )
   Sivers
                                 UT
                                          
                                       f1T  D1
   Pretzelosity
  AUT            sin(3h  S )       UT
                                             h1  H1
                                                T
         AUTsin() from transv. pol. H target
            Simultaneous fit to sin( + s) and sin( - s)
    `Collins‘ moments                          `Sivers‘ moments




• Non-zero   Collins asymmetry      •Sivers function nonzero (+)
                                     orbital angular momentum of quarks
• Assume q(x) from model, then
                                    •Regular flagmentation functions
     H1_unfav ~ -H1_fav
                                  M. Anselmino et al, PRD75,05032(2007)
• H1 (BELLE) (arXiv:0805:2975)
Experiments on polarized ``neutron’’ important!!

 Transverse Target SSA Measurement at Jefferson Lab Hall A
           Using a Polarized 3He Target (Neutron)
            First Experiment Completed Recently!
                 Jefferson Lab Hall A E06-010/E06-011
                              Collaboration
  California State Univ., Duke Univ., Florida International. Univ., Univ. Illinois, JLab, Univ. Kentucky,
 LANL,Univ. Maryland, Univ. Massachusetts, MIT, Old Dominion Univ., Rutgers Univ., Temple Univ.,
  Penn State Univ., Univ. Virginia, College of William & Mary, Univ. Sciences & Tech, China Inst. Of
Atomic Energy, Beijing Univ., Seoul National Univ., Univ. Glasgow, INFN Roma and Univ. Bari, Univ. of
                               Ljubljana, St. Mary’s Univ., Tel Aviv Univ.

                                 Collaboration members
   A.Afanasev, K. Allada, J. Annand, T. Averett, F. Benmokhtar, W. Bertozzi, F. Butaru, G. Cates, C.
     Chang, J.-P. Chen (Co-SP), W. Chen, S. Choi, C. Chudakov, E. Cisbani(Co-SP), E. Cusanno, R. De
        Leo, A. Deur, C. Dutta, D. Dutta, R. Feuerbach, S. Frullani, L. Gamberg, H. Gao(Co-SP), F.
            Garibaldi, S. Gilad, R. Gilman, C. Glashausser, J. Gomez, M. Grosse-Perdekamp, D.
      Higinbotham, T. Holmstrom, D. Howell, M. Iodice, D. Ireland, J. Jansen, C. de Jager, X. Jiang
       (Co-SP), Y. Jiang, M. Jones, R. Kaiser, A. Kalyan, A. Kelleher, J. Kellie, J. Kelly, A. Kolarkar, W.
    Korsch, K. Kramer, E. Kuchina, G. Kumbartzki, L. Lagamba, J. LeRose, R. Lindgren, K. Livingston,
        N. Liyanage, H. Lu, B. Ma, M. Magliozzi, N. Makins, P. Markowitz, Y. Mao, S. Marrone, W.
        Melnitchouk, Z.-E. Meziani, R. Michaels, P. Monaghan, S. Nanda, E. Nappi, A. Nathan, V.
     Nelyubin, B. Norum, K. Paschke, J. C. Peng (Co-SP), E. Piasetzky, M. Potokar, D. Protopopescu,
     X. Qian, Y. Qiang, B. Reitz, R. Ransome, G. Rosner, A. Saha, A. Sarty, B. Sawatzky, E. Schulte, S.
      Sirca, K. Slifer, P. Solvignon, V. Sulkosky, P. Ulmer, G. Urciuoli, K. Wang, Y. Wang, D. Watts, L.
      Weinstein, B. Wojtsekhowski, H. Yao, H. Ye, Q. Ye, Y. Ye, J. Yuan, X. Zhan, X. Zheng, S. Zhou.

                                                                                                         12
             Transversity from JLab Hall A

• Linear accelerator provides
  continuous polarized electron
  beam
   – Ebeam = 6 GeV
   – Pbeam = 85%
• 3 experimental halls



                                    A    B   C



                                                 13
          Jefferson Lab E06-010: Single Target-Spin
       Asymmetry in Semi-Inclusive n↑(e, e’±) Reaction on
              a Transversely Polarized 3He Target
                                 • Performed in Jefferson Lab Hall A
            16o                    from 10/24/08-2/6/09
                                 • Exceeded the approved goal
               g*
                         BigBite • 7 PhD students
                      30o        • First measurement of the neutron
HRSL                               Collins and Sivers asymmetries
                                      x = 0.1 - 0.4
                                • Upgraded polarized 3He target
                                      20 min fast spin-flip
        Polarized      e’             vertical polarization
       3He Target
                                      improved performance
                                 • BigBite for e and HRSL for  and K.
                  e              • BigBite detectors working well
                                 • Commissioned RICH in HRSL
   Nucleon Transversity at 11 GeV Using a
  Polarized 3He Target and SOLid in Hall A
               (Hall A Collaboration proposal)
                       (
Beijing U., CalState-LA, CIAE, W&M, Duke, FIU, Hampton, Huangshan U.,
Cagliari U. and INFN, INFN-Bari and U. of Bari, INFN-Frascati, INFN-Pavia,
Torino U. and INFN, JLab, JSI (Slovenia), Lanzhou U, LBNL, Longwood U,
LANL, MIT, Miss. State, New Mexico, ODU, Penn State at Berks, Rutgers,
Seoul Nat. U., St. Mary’s, Syracuse, Tel aviv, Temple, Tsinghua U, UConn,
Glasgow, UIUC, Kentucky, Maryland, UMass, New Hampshire, USTC, UVa
                         and the Hall A Collaboration
               Strong theory support,
Over 130 collaborators, 40 institutions, 8 countries
       including all 6 GeV transversity collaboration
Solenoid detector for SIDIS at 11 GeV
  (study done with Babar magnet, 1.5T)




                       GEMs
                GEMs: tracking device
      6 GEMs in total: positioned inside magnet
      (momentum, angle and vertex reconstruction);
      Forward angle: 8.5o to 16o (5 layers of GEM)
      Large angle: 16o to 25o to (4 layers GEM,
                   3 in common with Forward angle)




GEANT3 simulations show background rates in GEMs much less than the limit
      Particle identification
• Electron identification
   – Forward angle: CO2 gas Cerenkov/EM calorimeter
      • 2 m long, 1 atm CO2,,,threshold for pion 4.8 GeV/c
      • Shower plus Cerenkov provides better than 104:1 for pion
        rejection for 1.5 to 4.8 GeV/c momentum region
      • 200:1 for pion rejection for momentum greater than 4.8
        GeV/c (pion/e ratio < 1.5)
      • Multi-bounce mirror system for CO2 Cerenkov counter
   – Large angle
      • Electron momentum 4-6 GeV/c, expected pion/e ratio < 1.5
      • ``Shashlyk''-type calorimeter, pion rejection 200:1,
        efficiency for electron detection 99%
                     Electromagnetic Calorimeter




Pion rejection factor 200:1 for E> 2.0 GeV
Pion identification
 Combination of 1 atm CO2
 Cerenkov, a heavy gas
 Cerenkov, and an aerogel
 Cerenkov can reduce kaon
 Background to < 1%



        Particle     Pthreshold GeV/c   Pthreshold GeV/c
                          n=1.03            n=1.015
                        0.565              0.803
           K                2.0             2.840
           p             3.802              5.379
Acceptance
  Kinematic
  coverage

Black: forward angle
Green: large angle
Azimuthal angular coverage

    2π coverage for Spin, Collins,
     Sivers and Pretzelosity angle.
     – Important in disentangle all
       three terms.
    Symmetry in azimuthal angles
     can help reduce systematic
     uncertainties significantly.
              Single Spin Asymmetry
               1
                ( , ) Nh S 
            1 N h S  2 )
                       ( ,
       
     h
    A( , )
           P 1 N h S 
           (T N h S  2 )
     T
     U h S
             ) ( , )   ( ,
            2
      
    A( , ) 1 2
     h

           TT
     T
     U h S
           P P
      1
       ( , )2 h S  1 
      N h S N ) N h S ) 2
             ( ,     ( ,      ( , )
                            Nh S
      1
       ( , )2 h S  1 
      N h S N ) N h S ) 2
             ( ,     ( ,      ( , )
                            Nh S

 With full azimuzhal coverage,       Different from E06-010

    N( h, ),
     1 S                                   2 S
                                           N( h, ),
    N( h,  )
     1 S                                  2 S 
                                           N( h,  )
Simultaneously measured
Better control of systematic error   Simultaneously measured
Resolutions
Rates
                 Trigger and DAQ

   Option 1: Single electron rate ~ 110 kHz
    – Electron trigger: ECAL + GC + SC
    – DAQ will use the CODA3 and the pipeline
      technique being developed for Hall D
    – Expect zero dead time with 100 – 200 kHz trigger
      rate.
   Option 2: Coincidence rate ~ 90 kHz
    – Pion trigger:     ECAL + Aerogel + SC
    – Multi-DAQs to reduce trigger rate in each DAQ.
    – Will introduce some dead time.

         Need further studies
               Systematic Uncertainties
          Sources           Type                     Size
   Raw Asymmetry           absolute                1.1 E-3
Background Subtraction     relative                 1.0%


    Nuclear Effects        relative                 4-6%?
Diffractive Vector Meson   relative                 2-3%
 Radiative Correction      relative                  2%
    3He   Polarization     relative                  3%
           Total             N/A      6.0-7.7%(relative)+1.1E-3(absolute)



      Average Stat: 1.8e-3, Collins asymmetry ~2%
Projected results (ultimate precision in SSA)‫‏‬
                 7 more bins in z
Positive pions




Negative pions
Power of SOLid
                   Responsibilities
•   Aerogel Cerenkov detector: Duke, UIUC
•   CO2 gas Cerenkov detector: Temple U.
•   Heavy Gas Cerenkov Temple U.
•   ECal: W&M, UMass, JLab, Rutgers, Syracuse
•   GEM detectors:UVa, Miss State, W&M, Chinese
    Collaboration (CIAE, HuangshanU, PKU, LZU, Tsinghua,
    USTC), UKY, Korean Collaboration (Seoul National U)
•   Scintillator: Chinese Collaboration, Duke
•   Electronics: JLab                     blue: common with
•   DAQ: LANL, UVa and JLab               PVDIS
•   Magnet: JLab and UMass                Black: part in common with
                                          PVDIS
•   Simulation: JLab and Duke
                                          Red: This experiment only
    PAC decision: Defer with regret
    More simulations and studies to address the
    Concerns raised by the PAC
                       Summary
• The study of chiral-odd quark distribution (transversity,
  Sivers function, …) and fragmentation function (Collins
  function): an exciting, rapidly developing frontier,
  surprising flavor dependence observed in Collins and
  Sivers function,
   Worldwide effort – Completed the 1st experiment at JLab

• Future 11 GeV with Solenoid and polarized 3He target
  allows for a precision 3-d mapping of neutron Collins,
  Sivers, and pretzelocity asymmetries, and the extraction
  of transversity, Sivers and pretzlocity distribution
  functions.

• Together with world proton results provides model
  independent determination of tensor charge of d quark.
  Provide benchmark test of Lattice QCD calculations

								
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