Single Spin Asymmetries and Transverse Structure of the Nucleon
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Transcript of Single Spin Asymmetries and Transverse Structure of the Nucleon
Single Spin Asymmetries and Transverse Structure of the Nucleon
Jian-ping Chen ( 陈剑平 ) , Jefferson Lab, Virginia, USA Seminar @ USTC, Hefei, China, July 9, 2013
Introduction Recent SSA Results from JLab
New Preliminary SSA Results from JLab
TMD study with SoLID at JLab 12 GeV
SoLID Program on SSA/TMDs
Long-term Future: TMDs study with Electron-Ion Colliders (EIC)
MEIC@ JLab and E-RHIC@BNL
A New Opportunity: an EIC in China (EIC@HIAF)
Introduction
Strong QCD, Nucleon Structure/TMDs
What Are the Challenges?
• Success of the Standard Model Recent discovery of Higgs particle
Electro-Weak theory tested to very good level of precision
Strong interaction theory (QCD) tested in the high energy (short distance) region
• Major challenges: Understand QCD in the strong region (distance of the nucleon size)
Understand quark-gluon structure of the nucleon
Confinement
• Beyond Standard Model Energy frontier – LHC search: no new physics (yet)
Precision tests of Standard Model at low energy
Precision information of nucleon structure needed
QCD: Unsolved in Nonperturbative Region
• 2004 Nobel prize for ``asymptotic freedom’’
• non-perturbative regime QCD confinement• Nature’s only known truly
nonperturbative fundamental theory
• One of the top 10 challenges for physics!
• QCD: Important for discovering new physics beyond SM
• Nucleon: stable lab to study QCD• Nucleon structure is one of the
most active areas
running coupling “constant”
Electron Scattering and Nucleon Structure
• Clean probe to study nucleon structure only electro-weak interaction, well understood
• Elastic Electron Scattering: Form Factors 60s: established nucleon has structure (Nobel Prize) electrical and magnetic distributions
• Resonance Excitations internal structure, rich spectroscopy (new particle search) constituent quark models
• Deep Inelastic Scattering 70s: established quark-parton picture (Nobel Prize) parton distribution functions (PDFs)
polarized PDFs : spin Structure TMDs, GPDs: 3-d structure: Factorization: observable
J.T. Friedman R. Taylor H.W. Kendall
Nobel Prize 1990
Robert Hofstadter,
Nobel Prize 1961
SHA ~
F2 = 2xF1 g2 = 0
Nucleon Structure Function: Deep-Inelastic Scattering • Bjorken Scaling and Scaling Violation• Gluon radiation – QCD evolution• One of the best experimental tests of QCD
Polarized Structure Function/Distributions
QCD and Nucleon Structure Study
• Dynamical Chiral Symmetry Breaking <-> Confinement Responsible for ~98% of the nucleon mass Higgs mechanism is (almost) irrelevant to light quarks
• Rapid development in theory Lattice QCD Dyson-Schwinger Ads/CFT: Holographic QCD ……
• Direct comparisons limited to Moments Tensor charge …
• Direct comparison becomes possible Experimental data with predictions
from theory
Mass from nothing!
C.D. Roberts, Prog. Part. Nucl. Phys. 61 (2008) 50M. Bhagwat & P.C. Tandy, AIP Conf.Proc. 842 (2006) 225-227
Hall-A Collaboration Meeting: 13-14 June 2013
Craig Roberts: Mapping Parton Structure and Correlations (62p)
11
Established an one-to-one connection between DCSB and the pointwise form of the pion’s wave function.
Dilation measures the rate at which dressed-quark approaches the asymptotic bare-parton limit
Experiments at JLab12 can empirically verify the behaviour of M(p), and hence chart the IR limit of QCD
C.D. Roberts, Prog. Part. Nucl. Phys. 61 (2008) 50
Dilation of pion’s wave function is measurable in pion’s
electromagnetic form factor at JLab12
A-rated: E12-06-10
Imaging dynamical chiral symmetry breaking: pion wave function on the light front, Lei Chang, et al., arXiv:1301.0324 [nucl-th], Phys. Rev. Lett. 110 (2013) 132001 (2013) [5 pages].
Pion’s valence-quark Distribution Amplitude
Dyson-Schwinger
A new proposal
Using the Infinite Momentum Frame formalism. Start with static correlation in the z-direction.
X. Ji, to be published
First exploratory study by Huey-Wen Lin presented at the QCD Evolution Workshop at JLab, May 2013.
Lattice QCD
The extension of the approach
GPDs
TMDs
Single Spin Asymmetries with A Transversely Polarized 3He (n)
JLab Hall A E06-010Exploratory Measurements
Wpu(x,k
T,r ) Wigner distributions (X. Ji )
d2kT
PDFs f1
u(x), .. h1u(x)
GPDs/IPDs
d2kT drzd3r
TMD PDFs
f1u(x,kT), ..
h1u(x,kT) 3D imaging
6D Dist.
Form FactorsGE(Q2), GM(Q2)
d2rT
dx &Fourier Transformation
1D
Unified View of Nucleon Structure
Quark polarization
Unpolarized(U)
Longitudinally Polarized (L)
Transversely Polarized (T)
Nucleon Polarization
U
L
T
Leading-Twist TMD PDFs
f1 =
f 1T =
Sivers
Helicity
g1 =
h1 =Transversity
h1 =
Boer-Mulders
h1T =
Pretzelosity
h1L =
Worm Gear
: Survive trans. Momentum integration
Nucleon Spin
Quark Spin
g1T =
Worm Gear
Access TMDs through Hard Processes
proton
lepton lepton
pionproton
proton lepton
antilepton
Drell-Yan
BNLJPARC
FNAL
EIC
SIDIS
electron
positron
pion
pion
e–e+ to pions
Gauge invariant definition (Belitsky,Ji,Yuan 2003) Universality of kT-dependent PDFs (Collins,Metz 2003) Factorization for small kT. (Ji,Ma,Yuan 2005)
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
Transverity2011 Franco Bradamante
COMPASS Sivers asymmetry 2010 datax > 0.032 region - comparison with HERMES results
NEW
NEW
Status of Transverse Spin/Structure Study • Large single spin asymmetry in pp->pX (Fermi, RHIC-spin)• Collins Asymmetries - sizable for the proton (HERMES and COMPASS) large at high x, p- and +p has opposite sign unfavored Collins fragmentation as large as favored (opposite sign)?• Sivers Asymmetries - non-zero for p+ from proton (HERMES), new COMPASS data - large for K+ ? - sign mismatch?• Collins Fragmentation from Belle• Global Fits/models: Anselmino et al., Yuan et al., Pasquini et al., Ma et al., …• TMD evolution, a lot of progress in the last couple years• Very active theoretical and experimental efforts
JLab (6 GeV and 12 GeV), RHIC-spin, Belle, FAIR, J-PARC, EIC, …• First neutron measurement from Hall A 6 GeV (E06-010)• SoLID with polarized p and n(3He) at JLab 12 GeV Unprecedented precision with high luminosity and large acceptance
E06 010 Experiment‑Spokespersons: Chen/Evaristo/Gao/Jiang/Peng
• First measurement on n (3He)• Polarized 3He Target• Polarized Electron Beam, 5.9 GeV
• 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 p/K/p
TOF, RICH, Aerogel Cherenkov
• 7 PhD Thesis Students (All graduated) + new students (Yuxian Zhao, ...)
21
Beam Polarimetry(Møller + Compton)
LuminosityMonitor
XKeeHe ),(3
High luminosity: L(n) = 1036 cm-2 s-1
Record high 50-65% polarization in beam with automatic spin flip / 20min <P> = 55.4% ± 0.4% (stat. per spin state) ± 2.7 % (sys.)
22
Performance of 3He Target
~90% ~1.5% ~8%
Published Results (I) from JLab Hall A E06-010 with a Transversely Polarized 3He (n)
Collins/Sivers Asymmetries on p+/p-
Worm-Gear: Trans-helicity on p+/p-
X. Qian at al., PRL 107:072003(2011)
J. Huang et al., PRL. 108, 052001 (2012).
Neutron Results with Polarized 3He from JLab
Blue band: model (fitting) uncertainties Red band: other systematic uncertainties
X. Qian PRL 107 072003 (2011)
•
Sizable Collins π+ asymmetries at x=0.34?
– Sign of violation of Soffer’s inequality?
– Data are limited by stat. Needs more precise data!
•
Negative Sivers π+ Asymmetry– Consistent with HERMES/COMPASS– Independent demonstration of
negative d quark Sivers function.
E06-010 - First data on effectively neutron target Consistent with models in signs Suggest larger asymmetry, possible interpretations:
◦ Larger quark spin-orbital interference◦ different PT dependence◦ larger subleading-twist effects
Neutron ALT and Trans-Helicity g1T
Huang, et. al. PRL. 108, 052001 (2012) Access
Dominated by real part of interference between L=0 (S) and L=1 (P) states◦ Imaginary part -> Sivers effect
No GPD correspondence Measured by COMPASS and
HERMES on p and D targets
g1T =
Preliminary New Results (I) from JLab Hall A E06-010 with a Transversely Polarized 3He (n)
Collins/Sivers Asymmetries on K+/K-Analysis by Y. Zhao (USTC), Y. Wang (UIUC)
Pretzelosity Asymmetries for p+/p-Analysis by Y. Zhang (Lanzhou), X. Qian (Caltech)
Kaon PID by Coincidence time of flightCross checked with RICH results
K+/π+ ratio: ~5% K-/π- ratio: ~1%
Preliminary K+/K- Collins and Sivers Asymmetries on 3He
Pretzelosity Results on NeutronPretzelosity Asymmetries, For both p+ and p-, consistent with zero within uncertainties.
Preliminary Results
HERMES
Preliminary New Results (II)from JLab Hall A
Inclusive Electron SSA a Polarized 3He (n)
DIS Analysis by J. Katech(W&M), X. Qian (Caltech)Quasi-elastic by Y. Zhang (Rutgers), B. Zhao (W&M)
Inclusive Target Single Spin Asymmetry
3Heθ
e-
• Unpolarized e- beam incident on 3He target polarized normal to the electron scattering plane.
• However, Ay=0 at Born level, sensitive to physics at order α2; two-photon exchange.
Ay (Q2)
• In DIS case: related to integral of Sivers
• (Q)Elastic: Calculable at large Q2 using moments of GPD’s
• Measurement of Ay at large Q2 provides access to GPD’s
Inclusive Target SSA: DIS
neutron SSA from 3He(e,e’) Vertically polarized target
HERMES proton dataA. Airapetian et al,
Phys. Lett. B682, 351 (2010)Measured average:Ay = 0.94 ± 0.32 x 10-2
Preliminary QE 3He and neutron SSA results3He(e,e’) Ay
3He
neutron
GPD calculation
-- Q2 dependence in the quasi-elastic SSA, Ay
-- Agrees with GPD model** at Q2 = 1.0 GeV2.
-- TPEX important , -relevant for GE
p/GMp ?
Preliminary New Results (IV) from JLab Hall A E06-010 with a transversely polarized 3He (n)
Inclusive Hadron SSA
Analysis by K, Allada (JLab), Y. Zhao (USTC)
Inclusive Hadron Electroproduction
e + N↑ h + X (h = p, K, p)
Why a non-zero AN
is interesting?
– Analogues to AN in collision
– Simpler than due to only one quark channel – Same transverse spin effects as SIDIS and p-p collisions (Sivers, Collins, twist-3)– Clean test TMD formalism (at large p
T ~ 1 GeV or more)
– To help understand mechanism behind large AN in in the TMD framework
pT
pp↑→hX Ssin
UTTFN A=p,xA
pp↑→ hX
pp↑→ hX
ShNUT PxlSσ sin∼
Transverse SSA in Inclusive Hadron
• Target spin flip every 20 minutes• Acceptance effects cancels • Overall systematic check with A
N at ϕ
S= 0
– False asymmetry < 0.1%
0sin
=A SS
UT
N+N
NN=A S
UT
sin
p+ p-
False Asymmetry
0=PxlS hN
Preliminary
E06-010: Inclusive Hadron SSA (AN)
• Clear non-zero target SSA
• Opposite sign for p+ and p-
0 hN PxlS
0sin90=A S
SUT
Preliminary
E06-010: Inclusive Hadron SSA (AN)
• Clear non-zero target SSA
• Opposite sign for p+ and
p-
• AN at low p
T not very
well understood
0 hN PxlS
0sin90=A S
SUT
PreliminaryPreliminary
Future: TMD study with SoLID at 12 GeV JLab Hall A
Precision 4-D mapping of Collins/Sivers/Pretzelosity/Worm-Gear I/IIwith Polarized 3He (Neutron) and Proton
Di-Hadron Production
6 GeV JLab12
CHL-2
Upgrade magnets and power supplies
Enhance equipment in existing halls
add Hall D (and beam line)
H1, ZEUS
JLab Upgrade
11 GeV
H1, ZEUS
JLab @ 12 G
eV11 G
eV27 G
eV
200
GeV
W = 2 G
eV
0.7
HERMES
COMPASS
The 12 GeV Upgrade is well matched to studies in the valence quark regime.
Kinematics Coverage of the 12 GeV Upgrade
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
• SoLID: large acceptance, capable of handling high luminosity (up to~1039 with baffle, up to ~1037 without baffle)
Ideal for precision Inclusive-DIS (PVDIS) and SIDIS experiments Excellent for selected exclusive reactions (ex. J/Y)
• Five high impact experiments approved (4 with “A” rating, 1 A- rating): SIDIS: E12-10-006 (3He-T), E12-11-007 (3He-L), E12-11-108 (proton-T) PVDIS: E12-10-007 (deuteron and proton) J/y: E12-12-006
Physics Program for SoLID
SoLID Collaborators from China
Nucleon Structure (TMDs) with SoLID Semi-inclusive Deep Inelastic Scattering program: Large Acceptance + High Luminosity+ Polarized targets 4-D mapping of asymmetries Tensor charge, TMDs …Lattice QCD, QCD Dynamics, Models.
International collaboration (8 countries,50+ institutes and 190+ collaborators)• Rapid Growth in US China Collaboration‐Chinese Hadron collaboration(USTC, CIAE, PKU, Tsinghua U, Lanzhou, IMP,+)
- large GEM trackers- MRPC-TOF
3 A rated SIDIS experiments approved for SoLID with 2 having Chinese collaborators as co-spokesperson (Li from CIAE and Yan from USTC)
Solenoidal Large Intensity Device (SoLID)
Mapping of Collins/Siver Asymmetries with SoLID
E12-10-006 3He(n), Spokespersons: J. P. Chen, H. Gao, X. Jiang, J-C. Peng, X. QianE12-11-007(p) , Spokespersons: K. Allda, J. P. Chen, H. Gao, X. Li, Z-E. Mezinai
• Both p+ and p-• Precision Map
in region
x(0.05-0.65) z(0.3-0.7)
Q2(1-8)
PT(0-1.6)
• <10% u/d quark tensor charge
Map Collins and Sivers asymmetries in 4-D (x, z, Q2, PT)
Expected Improvement: Sivers Function
• Significant Improvement in the valence quark (high-x) region• Illustrated in a model fit (from A. Prokudin)
f 1T =
E12-11-107: Worm-gear functions (“A’ rating: )
Spokespersons: J. P. Chen/J. Huang/Y. Qiang/ W. Yan
• 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 =
Cent
er o
f poi
nts:
)()(~ 11 zDxgA TLT )()(~ 11 zHxhA LUL
h1L⊥(1)
S-P int.
P-D int.
Measure Transversity via Dihadron with SoLID LoI submitted to Jlab PAC 40, J. Zhang, J. P. Chen, A. Courtoy, H. Gao
Wide xb and Q2 coverages
Projected Statistics error for one (Mpp,zpp) bin, integrated over all y and Q2.
• Precision dihadron (p+/p-) production on a transversely polarized 3He (n) • Extract transversity on neutron• Provide crucial inputs for flavor separation of transversity talk by M.Radici
Projected Statistics Error
• Hall A, SoLID program• Polarized 3He target, (~60%
polarization)• Lumi=1036 (n)/s/cm2
• Wide xband Q2 coverages• Bin central values labeld on
axises• 4-d (xb, Q2, Zp+p-,Mp+p-) mapping• Z scale (color) represent stat.
error
Summary on SoLID TMD Program• Unprecedented precision 4-d mapping of SSA
• Collins, Sivers, Pretzelosity and Worm-Gear• Both polarized 3He (n) and 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 • learn quark orbital motion and quark orbital angular momentum• study Q2 evolution
• Global efforts (experimentalists and theorists), global analysis• much better understanding of multi-d nucleon structure and QCD
• Long-term future: EIC to map sea and gluon SSAs
Other SoLID Program
Parity Violating DISThreshold J/y Production
PVDIS with SoLIDE12-10-007: Contact Person: P. Souder
• High Luminosity on LD2 and LH2 • Better than 1% errors for small bins
over large range kinematics• Test of Standard Model • Quark structure:
charge symmetry violation
quark-gluon correlations
d/u at large-x
SoLID-J/ψ: Study Non-Perturbative Gluons
Quark Energy
Trace Anomaly
Gluon Energy
Quark Mass
50 days @ 1037 N/cm2/s
* /N N J
J/ψ: ideal probe of non-perturbative gluon
The high luminosity & large acceptance capability of SoLID enables a unique “precision” measurement near threshold
• Search for threshold enhancement• Shed light on the conformal anomaly
G G
X. Ji PRL 74 1071 (1995)
Long-term Future: TMD study with EIC
MEIC@JLab and E-RHIC@BNLNew Opportunity: EIC in China
An EIC with good luminosity & high transverse polarization is
the optimal tool to to study this!
Only a small subset of the (x,Q2) landscape has been mapped here.
Image the Transverse Momentum of the Quarks
Exact kT distribution presently essentially unknown!
Prokudin, Qian, Huang
Prokudin
RHIC eRHIC
LHC LHeC
CEBAF MEIC/EIC
FAIR ENC
HERA
EIC@HIAF
Electron Ion Colliders on the World Map
Lepton-Nucleon Facilities
JLAB12
HIAF
EIC@HIAF: e(3GeV) +p(12GeV), both polarized, L(max)=1033cm2/s
Main parameters and operation modes
EIC
HISCL
ICR-45
ECR
LIS
CBR-15ABR-25
ER
Electron injector
RIBs line
6.0 GeV (p)2.8×1012
50 MeV/u (p)1 pmA
1 Hz, 680 μs
12.0 GeV (p)4.1×1012
3.0 GeV (e)3.0×1013
EIC
3.0 GeV (e)
EIC@HIAF Kinematic Coverage Comparison with JLab 12 GeV
e(3GeV) +p(12GeV), both polarized, L(max)=4x1032cm2/s
EIC@HIAF:• study sea quarks (x > 0.01)• deep exclusive scattering at
Q2 > 5-10• higher Q2 in valance region• range in Q2 allows study
gluons
• Timeline: Funding Approved for HIAF. EIC under design/discussion Construction 2014-2019 (2022).
plot courtesy of Xurong Chen
The Science of eRHIC/MEIC
Goal: Explore and Understand QCD: Map the spin and spatial structure of quarks and gluons in nucleons Discover the collective effects of gluons in atomic nuclei
(role of gluons in nuclei & onset of saturation)Emerging Themes: Understand the emergence of hadronic matter from quarks and gluons & EW
The Science of EIC@HIAF
One Main Goal: Explore Hadron Structure Map the spin-flavor, multi-d spatial/momentum structure of valence & sea quarks
Science Goals
TMD Study and other Programs at EIC@HIAF• Unique opportunity for TMD in “sea quark” region
reach x ~ 0.01 (JLab12 mainly valence quark region, reach x ~ 0.1) • Significant increase in Q2 range for valence region
energy reach Q2 ~40 GeV2 at x ~ 0.4 (JLab12, Q2 < 10)• Significant increase in PT range
reach >1 GeV? (TMD/co-linear overlap region) (JLab12, reach <1 GeV) • Other Physics Programs:
Nucleon spin-flavor structure (polarized sea, Ds)
3-d Structure: GPDs (DVMP, pion/Kaon)
e-A to study hadronization
Pion/Kaon structure functions?
……
2nd Conference on QCD and Hadron Physics: http://qcd2013.csp.escience.cn/dct/page/1
Whitepaper on EIC@China is being worked on:
need inputs and help from international community
Green (Blue) Points: SoLID projections for polarized NH3 (3He/n) targetLuminosity: 1035 (1036) (1/cm2/s); Time: 120 (90) days
Black points: EIC@HIAF projections for 3 GeV e and 12 GeV pLuminosity: 4 x 1032 /cm2/s; Time: 200 days
The TMD simulation: Projections for SIDIS Asymmetry π+
Duke group
EIC@HIAF reach similar precision as SoLID at lower x, higher Q2 region
Physics Programs at EIC@HIAF
Opportunity to bring Chinese hadron physics to the forefront in the world
• Unique opportunity for TMD in “sea quark” region
and significant increase in Q2 / PT range for valence region
• Nucleon spin-flavor structure (polarized sea, Ds) • 3-d Structure: GPDs (DVMP, pion/Kaon)• e-A to study hadronization • Pion/Kaon structure functions• EMC-SRC in e-A
……
2nd Conference on QCD and Hadron Physics: http://qcd2013.csp.escience.cn/dct/page/1
Whitepaper on EIC@China is being worked on:
need inputs and help from international community
Summary
• Rapid progress in non-perturbative QCD and nucleon structure• SSA and TMD study have been exciting and fruitful• Recent and Preliminary Results from JLab Hall A Collins/Sivers asymmetries for p+/p-/K+/K-
Pretzelosity on pi+/pi-SSA: inclusive hadronSSA: inclusive electron DIS and (Quasi)Elastic
• Planned SoLID program with JLab12 Precision 4-d mapping of TMD asymmetries
• EIC@HIAF will bring China to forefront in the world in hadron physics Exciting new opportunities
Precision experimental data + development in TMD theory + nonperturbative QCD lead to breakthrough in understanding QCD