Highlights of Spin Study at JLab Hall A: Longitudinal and Transverse J. P. Chen, Jefferson Lab Pacific-Spin2011, Cairns, Australia Introduction Longitudinal and transverse spin Selected results from JLab Hall A SSA in SIDIS: Transversity and TMDs g 2 (d 2 ) at intermediate to high Q 2 : higher- twists, B-C sum rule g 1 /g 2 at low Q 2 : GDH sum/spin polarizabilities Future experiments (6 GeV and 12 GeV)
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Highlights of Spin Study at JLab Hall A: Longitudinal and Transverse J. P. Chen, Jefferson Lab Pacific-Spin2011, Cairns, Australia Introduction Longitudinal.
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Highlights of Spin Study at JLab Hall A: Longitudinal and Transverse
J. P. Chen, Jefferson LabPacific-Spin2011, Cairns, Australia
Introduction
Longitudinal and transverse spin
Selected results from JLab Hall A
SSA in SIDIS: Transversity and TMDs
g2 (d2) at intermediate to high Q2: higher-twists, B-C sum rule
g1/g2 at low Q2: GDH sum/spin polarizabilities
Future experiments (6 GeV and 12 GeV)
Spin Milestones (I)
• Nature: (www.nature.com/milestones/milespin) 1896: Zeeman effect (milestone 1) 1922: Stern-Gerlach experiment (2) 1925: Spinning electron (Uhlenbeck/Goudsmit)(3) 1928: Dirac equation (4) Quantum magnetism (5) 1932: Isospin(6) 1935: Proton anomalous magnetic moment 1940: Spin–statistics connection(7) 1946: Nuclear magnetic resonance (NMR)(8) 1950s: Development of magnetic devices (9) 1950-51: NMR for chemical analysis (10) 1951: Einstein-Podolsky-Rosen argument in spin variables(11) 1964: Kondo Effect (12) 1971: Supersymmetry(13) 1972:Superfluid helium-3 (14)
Spin Milestones (II) 1973: Magnetic resonance imaging(15) 1975-76:NMR for protein structure determination (16) 1978: Dilute magnetic semiconductors (17) 1980s: “Proton spin crisis or puzzle” 1988: Giant magnetoresistance(18) 1990: Functional MRI (19) Proposal for spin field-effect transistor (20) 1991: Magnetic resonance force microscopy (21) 1996: Mesocopic tunnelling of magnetization (22) 1997: Semiconductor spintronics (23) (Spin-polarized suprecurrents for spintronics, 1/2011) 2000s: “Nucleon transverse spin puzzle”? ?: More puzzles in nucleon spin? …… ?: Breakthroughs in nucleon spin/nucleon structure study? …… ?: Applications of nucleon spin physics?
Nucleon Structure, Moments and Sum Rules
• Global properties and structure
Mass: 99% of the visible mass in universe
~1 GeV, but u/d quark mass only a few MeV each!
Momentum: quarks carry ~ 50% Energy-Momentum Sum Rule
Spin: ½, quarks contribution ~30% Spin Sum Rule(s)
Magnetic moment: large part anomalous, >150% GDH Sum Rule
Axial charge Bjorken Sum Rule
Angular momentum Ji’s Sum Rule
Polarizabilities (Spin, Color)
Tensor charge
Three Decades of Spin Structure Study• 1980s: EMC (CERN) + early SLAC quark contribution to proton spin is very small = (12+-9+-14)% ! ‘spin crisis’ (Ellis-Jaffe sum rule violated)
• 1990s: SLAC, SMC (CERN), HERMES (DESY) = 20-30% the rest: gluon and quark orbital angular momentum
A+=0 (light-cone) gauge (½) + Lq+ G + Lg=1/2 (Jaffe)
gauge invariant (½) + Lq + JG =1/2 (Ji) A new decomposition (X. Chen, et. al) What observable directly corresponds to Lz~ bx X py ? Bjorken Sum Rule verified to <10% level
• 2000s: COMPASS (CERN), HERMES, RHIC-Spin, JLab, … : ~ 30%;G probably small, orbital angular momentum probably significant Sum Rules at low Q2
13 completed experiments 7 approved with 12 GeV (A/C)
15 uA
JLab Polarized Proton/Deuteron Target
• Polarized NH3/ND3 targets
• Dynamical Nuclear Polarization
• In-beam average polarization
70-90% for p
30-40% for d• Luminosity up to ~ 1035 (Hall C/A)
~ 1034 (Hall B)
JLab Spin Experiments
• Results:• SSA in SIDIS: Transversity (n)/ TMDs• g2/d2: Higher twists, B-C sum rule• Spin Moments: Spin Sum Rules and Polarizabilities• Quark-Hadron duality• Spin in the valence (high-x) region
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
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A
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A
1
1 1
1
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sin( )
sin(3 )
sin( )Co
PretzelosityU
SiversUT
llins
T h S T
h S
UT
UT h S
TU
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TA
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f
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D
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Current Status• Large single spin asymmetry in pp->X• Collins Asymmetries
- sizable for proton (HERMES and COMPASS) large at high x,- and has opposite sign unfavored Collins fragmentation as large as favored (opposite sign)? - consistent with 0 for deuteron (COMPASS)
• Sivers Asymmetries - non-zero for + from proton (HERMES), consistent with zero (COMPASS)? - consistent with zero for - from proton and for all channels from deuteron - large for K+ ?
• Very active theoretical and experimental study RHIC-spin, JLab (Hall A 6 GeV, CLAS12, HallA/C 12 GeV), Belle, FAIR (PAX)
• Global Fits/models by Anselmino et al., Yuan et al. and …
• First neutron measurement from Hall A 6 GeV (E06-010)
• Solenoid with polarized 3He at JLab 12 GeV Unprecedented precision with high luminosity and large acceptance
E06 010 Experiment ‑• First measurement on n (3He)• Polarized 3He Target• Polarized Electron Beam, 5.9 GeV
– ~80% Polarization– Fast Flipping at 30Hz
• BigBite at 30º as Electron Arm– Pe = 0.7 ~ 2.2 GeV/c
• HRSL at 16º as Hadron Arm– Ph = 2.35 GeV/c – Excellent PID for /K/p
• 7 PhD Thesis Students (5 graduated)
16
Beam Polarimetry(Møller + Compton)
LuminosityMonitor
XeeHe ),(3
History of Figure of Merit of Polarized 3He Target
• High luminosity: L(n) = 1036 cm-2 s-1
• Record high in-beam ~ 60% polarization with 15 A beam with automatic spin flip every 20 minutes
Performance of 3He Target
In-beam 3He pol. 55-60%
3He Target Single-Spin Asymmetry in SIDIS
3He Sivers SSA:negative for π+,
3He Collins SSA small Non-zero at highest x for +
Blue band: model (fitting) uncertainties Red band: other systematic uncertainties
arXiv: 1106.0363, submitted to PRL
Results on Neutron
Collinsasymmetries are not large, except at x=0.34
Sivers negative
Blue band: model (fitting) uncertainties Red band: other systematic uncertainties
• Consist w/ model in signs, suggest larger asymmetry
Neutron ALT Extraction
Preliminary
hq
qT
n DgA 11LT
JLab 12 GeV Era: Precision Study of TMDs
• From exploration to precision study with 12 GeV JLab• Transversity: fundamental PDFs, tensor charge• TMDs: 3-d momentum structure of the nucleon Quark orbital angular momentum• Multi-dimensional mapping of TMDs
• 4-d (x,z,P┴,Q2)
• Multi-facilities, global effort
• Precision high statistics• high luminosity and large acceptance
Solenoid detector for SIDIS at 11 GeVAlso for PVDIS at 11 GeV
Approved SIDIS experiments: E10-006 & E11-007
SSA in SIDIS Pion Production Transversely/ Longitudinally Polarized 3He Target at 8.8 and 11 GeV.
Large acceptance: >100 msr
High luminosity : > 1036
Mapping of Collins/Siver Asymmetries with SoLID
• Both + and -
• For one z bin
(0.4-0.45)
• Will obtain many z bins (0.3-0.7)
• Upgraded PID for K+ and K-
Map Collins and Sivers asymmetries in 4-D (x, z, Q2, PT)
Worm-gear functions:• Dominated by real part of interference
between L=0 (S) and L=1 (P) states• No GPD correspondence• Lattice QCD -> Dipole Shift in mom. space.• Model Calculations -> h1L
=? -g1T .
h1L =
g1T =
Worm Gear
Cent
er o
f poi
nts:
)()(~ 11 zDxgA TLT )()(~ 11 zHxhA LUL
Discussion• Unprecedented precision 4-d mapping of SSA
• Collins and Sivers• +, - and K+, K-
• New proposal polarized proton with SoLID• Study factorization with x and z-dependences • Study PT dependence• Combining with the world data
• extract transversity and fragmentation functions for both u and d quarks• determine tensor charge• study TMDs for both valence and sea quarks • study quark orbital angular momentum• study Q2 evolution
• Global efforts (experimentalists and theorists), global analysis• much better understanding of multi-d nucleon structure and QCD
• Longer-term future: EIC to map sea and gluon SSAs
Inclusive Transverse Spin
g2 Structure Function and Moments Burkhardt - Cottingham Sum Rule
A. Deur, V. Burkert, J. P. Chen and W. Korsch PLB 650, 244 (2007) and PLB 665, 349 (2008)
Spin Polarizabilities
Higher Moments of Spin Structure Functions at Low Q2
Higher Moments: Generalized Spin Polarizabilities
• generalized forward spin polarizability 0
generalized L-T spin polarizability LT
dxxQgxQ
MxQgx
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M
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)],(4
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22
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LTLT
dxxQgxQgxQ
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QQKQ
Neutron Spin Polarizabilities LT insensitive to resonance• RB ChPT calculation with resonance for 0 agree with data at Q2=0.1 GeV2 • Significant disagreement between data and both ChPT calculations for LT
• Good agreement with MAID model predictions
0 LT
Q2
Q2
E94-010, PRL 93 (2004) 152301
Preliminary Results from E97-110• Significant disagreement between data and both ChPT calculations for LT
• Good agreement with MAID model predictions
0 LT
Q2
Q2
Axial Anomaly and the LT Puzzle
N. Kochelev and Y. Oh; arXiv:1103.4891v1
E08-027 : Proton g2 Structure Function Fundamental spin observable has never been measured at low or moderate Q2
BC Sum Rule : violation suggested for proton at large Q2, but found satisfied for the neutron & 3He.
Spin Polarizability : Major failure (>8 of PT for neutron LT. Need g2 isospin separation to solve.
Hydrogen HyperFine Splitting : Lack of knowledge of g2 at low Q2 is one of the leading uncertainties.
Proton Charge Radius : also one of the leading uncertainties in extraction of <Rp> from H Lamb shift.
• Spin structure study full of surprises and puzzles• A decade of experiments from JLab: exciting results
• first neutron transversity/TMD measurement• precision measurements of g2/d2: high-twist• spin sum rules and polarizabilities• test PT calculations, ‘LT puzzle’ • valence spin structure, quark-hadron duality
• Bright future• complete a chapter in spin structure study with 6 GeV JLab• 12 GeV Upgrade will greatly enhance our capability
• Precision determination of the valence quark spin structure• Precision multi-d map of TMDs/transverse spin/tensor charge• Precision extraction of GPDs, 3-d structure
• EIC: precision determination of sea and gluon in multi-d• Goal: a full understanding of nucleon structure and QCD• Lead to breakthrough in strong interaction?