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
quark-gluon correlations
-- confinement
interaction strong at low energy
coherent hadron
-- Chiral symmetry
-- theoretical tools:
pQCD, OPE, Lattice QCD, ChPT
• Charge and magnetism
(current) distribution E
– Nucleon: Electric GE
and magnetic GM form
factor
• Spin distribution
• Quark momentum and
flavor distribution
• Polarizabilities
• Strangeness content
• …..
Leading-Twist Quark Distributions
( Eight parton distributions functions)
nonvanishing
integrating
over K 
Transversity:
K - dependent,
T-odd
K - dependent,
T-even
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 SemiInclusive DIS
d
2
y2


2
2
dxdydS dzdh dPh xyQ 2(1   )
{FUU ,T  ...
Boer-Mulder
cos( 2h )
UU
  cos(2h )  F
 ...
Unpolarized
sin( 2h )
 S L [ sin(2h )  FUL
 ...]
Transversity
Sivers
Pretzelosity
sin(h S )
 ST [ sin(h  S )  FUT
sin(h S )
 sin(h  S )  ( FUL
 ...)
Polarized
Target
sin(3h S )
  sin(3h  S )  FUT
 ...]
 S L e [ 1   2  FLL  ...]
Polarized
Beam and
cos(h S )
2
 ST e [ 1   cos(h  S )  FLT
 ...]} Target
SL, ST: Target Polarization; e: Beam Polarization
Separation of Collins, Sivers and pretzelocity effects
through angular dependence


1
N

N
AUT (hl ,  Sl ) 
P N  N
Collins
Sivers
 AUT
sin(h  S )  AUT
sin(h  S )
ty
 AUPretzelosi
sin(3h  S )
T
Collins
AUT
 sin(h  S )
Sivers
AUT
 sin(h  S )
UT
UT
 h1  H1
 f1T  D1
AUPretzelosity
 sin(3h  S )
T
UT
 h1T  H1
AUTsin() from transv. pol. H target
Simultaneous fit to sin( + s) and sin( - s)
`Collins‘ moments
`Sivers‘ moments
• Non-zero
Collins asymmetry
• Assume q(x) from model, then
H1_unfav ~ -H1_fav
• H1 (BELLE) (arXiv:0805:2975)
•Sivers function nonzero (+)
orbital angular momentum of quarks
•Regular flagmentation functions
M. Anselmino et al, PRD75,05032(2007)
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
16o
g*
HRSL

Polarized
3He Target
e
• Performed in Jefferson Lab Hall A
from 10/24/08-2/6/09
• Exceeded the approved goal
BigBite • 7 PhD students
• First measurement of the neutron
30o
Collins and Sivers asymmetries
 x = 0.1 - 0.4
• Upgraded polarized 3He target
 20 min fast spin-flip
e’
 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
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
n=1.03
Pthreshold GeV/c
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
(
N

)
1 N
1
h, S)
2(
h, S
A(
, ) 
(P
(
N

, S
)
T) N
1
h, S)
2(
h
h
U
T h S
2
A(
, ) 1 2
P
P
T
T
h
U
T h S
N
(
N

) N
(
, S
)N
(
, S)
1
h, S)
2(
h, S
1
h
2
h
N
(
N

) N
(
, S
)N
(
, S)
1
h, S)
2(
h, S
1
h
2
h
With full azimuzhal coverage,
N
h,S),
1(
N
h,S )
1(
Simultaneously measured
Better control of systematic error
Different from E06-010
N2(h,S),
N2(h,S )
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%
relative
3%
N/A
6.0-7.7%(relative)+1.1E-3(absolute)
3He
Polarization
Total
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
Black: part in common with
Magnet: JLab and UMass
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