the study of neutron transversity from a polarized 3 he target at 12 gev jlab haiyan gao ( 高海燕...
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The Study of Neutron Transversity from a
Polarized 3He Target at 12 GeV JLab
Haiyan Gao (高海燕 )
Duke University/TUNL
Durham, NC, U.S.A.
A Workshop on Hadron Physics in China and Opportunities with 12 GeV JLab
July 31- August 1, 2009 Lanzhou University, Lanzhou, China
(
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
quark-gluon correlations
-- confinement
interaction strong at low energy
coherent hadron
-- Chiral symmetry
-- theoretical tools:
pQCD, OPE, Lattice QCD, ChPT
E
• Charge and magnetism (current) distribution– Nucleon: Electric GE
and magnetic GM form factor
• Spin distribution • Quark momentum and
flavor distribution• Polarizabilities• Strangeness content• …..
Leading-Twist Quark Distributions
non-vanishing integrating
over
K - dependent, T-odd
K - dependent, T-even
( Eight parton distributions functions)
Transversity:
K
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
...]})cos(1[
...]1[
...])3sin(
...)()sin(
)sin([
...])2sin([
...)2cos(
...{
)1(2
)cos(2
2
)3sin(
)sin(
)sin(
)2sin(
)2cos(
,
2
2
2
2
Sh
Sh
Sh
Sh
h
h
LTSheT
LLeL
UTSh
ULSh
UTShT
ULhL
UUh
TUU
hhS
FS
FS
F
F
FS
FS
F
F
y
xyQdPdzddxdyd
d
Unpolarized
PolarizedTarget
PolarizedBeam andTarget
SL, ST: Target Polarization; e: Beam Polarization
Boer-Mulder
Sivers
Transversity
Pretzelosity
Separation of Collins, Sivers and pretzelocity effects through angular dependence
1( , )
sin( ) sin( )
sin(3 )
l lUT h S
h SSiverCollins
Pretzelosi
UT
tyU
sUT h S
h ST
N NA
P N
A
A
N
A
1
1 1
1
1 1
sin( )
sin(3 )
sin( )Co
PretzelosityU
SiversUT
llins
T h S T
h S
UT
UT h S
TU
UT
TA
H
f
A
D
A h H
h
AUTsin() from transv. pol. H target
Simultaneous fit to sin( + s) and sin( - s) `Collins‘ moments
• Non-zero Collins asymmetry
• Assume q(x) from model, then
H1_unfav ~ -H1_fav
• H1 (BELLE) (arXiv:0805:2975)
`Sivers‘ moments
•Sivers function nonzero (+) orbital angular momentum of quarks
•Regular flagmentation functions
M. Anselmino et al, PRD75,05032(2007)
Transverse Target SSA Measurement at Jefferson Lab Hall A Using a Polarized 3He Target (Neutron)
First Experiment Completed Recently!
Experiments on polarized ``neutron’’ important!!
12
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.
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.
Collaboration members
Transversity from JLab Hall A
• Linear accelerator provides
continuous polarized electron
beam
– Ebeam = 6 GeV
– Pbeam = 85%
• 3 experimental halls
13
A B C
e
e’
HRSL
BigBite
16o
30o
Polarized3He Target
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 from 10/24/08-2/6/09
• Exceeded the approved goal• 7 PhD students• First measurement of the neutron
Collins and Sivers asymmetries x = 0.1 - 0.4
• Upgraded polarized 3He target 20 min fast spin-flip vertical polarization improved performance
• BigBite for e and HRSL for and K.• 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
GEMs: tracking device6 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 identificationParticle 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%
Pion identification
5.3793.802p
2.8402.0K
0.8030.565
Pthreshold GeV/c
n=1.015
Pthreshold GeV/c
n=1.03
Particle
Combination of 1 atm CO2
Cerenkov, a heavy gas Cerenkov, and an aerogelCerenkov can reduce kaonBackground to < 1%
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.
1 2
1 2
1 2
1 2 1 2
1 2 1 2
( , ) ( , )1( , )
( ) ( , ) ( , )
2( , )
( , ) ( , ) ( , ) ( , )
( , ) ( , ) ( , ) ( , )
h h S h SUT h S
T h S h S
hUT h S
T T
h S h S h S h S
h S h S h S h S
N NA
P N N
AP P
N N N N
N N N N
Single Spin Asymmetry
With full azimuzhal coverage,
),(
),,(
1
1
Sh
Sh
N
N
),(
),,(
2
2
Sh
Sh
N
N
Simultaneously measuredBetter control of systematic error Simultaneously measured
Different from E06-010
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
6.0-7.7%(relative)+1.1E-3(absolute)N/ATotal
3%relative3He Polarization
2%relativeRadiative Correction
2-3%relativeDiffractive Vector Meson
4-6%?relativeNuclear Effects
1.0%relativeBackground Subtraction
1.1 E-3absoluteRaw Asymmetry
SizeTypeSources
Average Stat: 1.8e-3, Collins asymmetry ~2%
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• DAQ: LANL, UVa and JLab• Magnet: JLab and UMass• Simulation: JLab and Duke
PAC decision: Defer with regretMore simulations and studies to address the Concerns raised by the PAC
blue: common withPVDISBlack: part in common with PVDISRed: This experiment only
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