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