Kalyan AlladaMassachusetts Institute of Technology

User Group Meeting, Jefferson LabJune 3, 2015

Overview of Results from the Transversity Experiment (E06-010)

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Semi-Inclusive DIS

• Detection of leading hadron enables “flavor tagging” of the struck quark• Access to transversity distribution and TMDs• Transverse Momentum Dependent PDFs

– Links intrinsic parton motion(kqT) and parton spin(sq

T), to nucleon spin (SNT)

– Provides access to quark OAM through spin-orbit correlations

– Provides 3-D imaging of quarks in momentum space– Access to quark-gluon-quark correlations through

higher-twist observables

ν=E−E 'x=Q2 /2M ν

y=ν/Ez=Eh /ν

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Transverse Momentum Dependent Quark Distributions (TMDs)

Unpolarized

Polarized target

Polarized beam andtarget

Transversity

Sivers

Boer-Mulders

Worm-gear

Pretzelosity

Worm-gear

Accessible through Semi-inclusive DIS reaction

Helicity

ST and S

L are target polarization and λ

e is beam polarization

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Leading Twist TMDs

TMDs sensitive to transversely polarized nucleon

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Hall A Transversity Experiment

• Run Period : Oct 2008 – Jan 2009• Beam Energy: 5.9 GeV, polarized, 30Hz spin-flip • Target:

• 3He : transversely and vertically polarized• In beam polarization: ~60%• Spin flips: every 20 minutes

• Collected both coincidence and singles triggers• Measured π+/−, K+/− electroproduction• Measured Single and double spin asymmetries (AUT, ALT)

Azimuthal Moments in SIDIS

Single Spin Asymmetry

Azimuthal Moments in SIDIS

ST

Separate different effects through azimuthal angular dependence

Collins moment

Sivers moment:

Pretzelosity:

Worm-gear:

Target spin orientations: up-down and left-right (increase angular coverage)

Automatic target spin-flip every 20 mins (keeps systematics due to target under control)

ST = Nucleon Spin direction

Azimuthal Angular Coverage

Collins angle: ɸh+ ɸs Sivers angle: ɸh- ɸs

Different colors corresponds to different target spin states: left, right, up and down

K+/π+ ratio: ~5% K-/π- ratio: ~1%

Pions were suppressed using Aerogel counter (A1) when selecting Kaons

Particle Identification

BigBite

BigBite +HRS

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Neutron Collins and Sivers Moments (AUT

)

X. Qian et al., PRL 107 (2011) 072003

Collins and Sivers Moments

● Neutron SSA extracted from measured 3He asymmetry in SIDIS

● Covers valence region

● Non-zero π+ Collins at x = 0.34 ?

● Favors negative values for π+ Sivers

● Neutron Collins and Sivers moments consistent with models predictions (2011)

First measurement of 3He (neutron) Transverse SSA

Blue band: model (fitting) uncertainties Red band: other systematic uncertainties

Global Extraction of Transversity

Transversity distribution

Global analysis of transversity:includes HERMES (p), COMPASS (p/d) and JLab (3He) data

Z-B. Kang et al., arXiv:1505.05589

http://arXiv.org/abs/arXiv:1505.05589

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Pretzelosity Asymmetry (AUT

)

Pretzelosity SSA

Y. Zhang et al., PRC 90 (2014) 055209

● In some relativistic quark models directly related to quark OAM

● Extracted neutron moments consistent with zero within uncertainties

● Pretzelosity is suppressed by k2T /M2

compared to the Sivers moment

h1T⊥ =g1−h1

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Beam-Target Double Spin Asymmetry (ALT

)

J. Huang et al. PRL. 108, 052001 (2012)

● Related to real part of L=0, L=1 interference Imaginary part => Sivers DF

● Clear non-zero ALT

observed for π− ● Consistent in sign with models

A non-vanishing quark “transversal helicity” distribution, reveals alignment of quark spin transverse to neutron spin direction - quark orbital motion!

ALT

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Collins and Sivers SSA of Kaons from 3He (neutron)

● Both Collins and Sivers K+ asymmetry is consistent with zero within experimental uncertainties

● Low statistics for K- (one bin): ● K- asymmetry favors negative values● K- Sivers asymmetry different from

prediction

● No predictions for Collins asymmetry - lack of information on kaon fragmentation function

Y. X. Zhao, et al., Phys. Rev. C 90, 055201 (2014)

Important contribution to the global kaon SSA data (others include HERMES, COMPASS on proton target) for the extraction of sea quark TMDs

Kaon SSA from neutron

Predictions from global fit M. Anselmino et al., Eur. Phys. J. A39, 89 (2009).

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Transverse SSA in Inclusive Hadron Production

● Only one hard scale : PT of the detected hadron

● Relevant kinematic variables: – pT : Transverse momentum of hadron– : pL is the long. momentum of hadron

● Assuming TMD factorization valid in inclusive hadron production:● Sivers contribution dominates SSA● Collins contribution is negligible

e + 3He↑ h + X (h = π/K/p)

M. Anselmino et al., Phys. Rev. D81, 034007 (2010)

pT

x F≃2pL/ s

http://dx.doi.org/10.1103/PhysRevD.81.034007

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Transverse SSA in Inclusive Hadron Production

3He asymmetry

ϕs= 90o

ϕs= 0o

● AN for ϕ

s= 0o indicate false asymmetry less than 0.1%

● Clear non-zero SSA observed for π+/-, K+ at ϕs= 90o

● π+ and π- have opposite sign

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Transverse SSA in Inclusive Hadron Production

K. Allada, et al.Phys. Rev. C 89, 042201(R)

● Clear non-zero SSA observed for π+/−, K+● No theoretical prediction at low P

T

● Data agrees in sign with predictions from twist-3 collinear factorization (for P

T>1.0 GeV)

● Similar behavior compared to AN in pp↑-->hX

3He asymmetry Neutron asymmetry

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Transverse DSA in Inclusive Hadron Production

• ALT in inclusive hadron is a sub-leading twist observable in collinear factorization• Collinear twist-3 contributions from both distribution and fragmentation side• Related to collinear twist-3 “Worm-Gear” type function

learn about q-g-q correlations in the nucleon Twist-3 effects in fragmenting hadron

e + 3He↑ h + X (h = π/K/p)

g̃(x )

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Transverse DSA in Inclusive Hadron Production

3He Asymmetry for charged hadrons

3He asymmetry for charged pions(p

T distribution)

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Transverse DSA in Inclusive Hadron Production

Y.X.Zhao et al. arXiv:1502.01394(under review in Phys. Rev. C)

● Clear non-zero SSA observed for π+/−● π+ and π− SSA have opposite sign● Model predictions:

● using WW-type approx agrees in sign● using Sivers-type approx do not agree

3He asymmetry Neutron asymmetry

Predictions from K. Kanazawa et al., arXiv:1411.6459 (2014)

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Transverse Target SSA in Inclusive DIS (Ay)

Upolarized beam, trasversely polarized nucleon

Target Single Spin Asymmetry:

● dσUT

µ Im (M1γ

M*1γ

) is zero at Born level – time-reversal invariance● dσ

UT µ Im (M

1γM*

2γ ) is non-zero with one and two-photon interference terms

● Two parton-model predictions of two-photon exchange contributions to Ay

● Two-photon exchange with a single quark (A. Afanasev et al.)A

y ~ 10-4, at x ~ 0.3 and Q2 ~ 2.0 GeV2

● Two-photon exchange with two difference quarks (struck and spectator di-quark)A

y ~ -10-2 ( A. Metz et al., and M. Schlegel et al.)

● HERMES proton data at Q2 > 1 GeV2 consistent with zero at ~10-3 level

e + 3He↑ e' + X

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First non-zero measurement of Ay (3σ). Consistent with Metz et al.

using Sivers input.

Ay on Neutron from inclusive DIS Data (JLab Expt. E07-013)

J. Katich et al., Phys. Rev. Lett. 113 (2014) 022502

Data from singles trigger in the BigBite and HRS

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Summary of Results

Published Results (2011 - 2015) :● Charged pions SSA in semi-inclusive DIS (Collins and Sivers moments)

● X. Qian et al., Phys. Rev. Lett. 107, (2011) 072003

● Charged pion DSA in semi-inclusive DIS (g1T

)● J. Huang et al., Phys. Rev Lett. 108, (2012) 052001

● SSA in inclusive DIS production (TPE) (JLab expt. E07-013) ● J. Katich et al., Phys. Rev. Lett. 113 (2014) 022502

● Charged hadron (π/k/p) SSA in inclusive hadron production (AN)

● K. Allada et al., Phys. Rev. C 89 (2014) 042201 (Rapid Comm.)

● Charged pion SSA in semi-inclusive DIS (Pretzelosity) ● Y. Zhang et al., Phys. Rev. C 90 (2014) 5, 055209

● Charged Kaon SSA in semi-inclusive DIS (Collins and Sivers moments)● Y. X. Zhao et al., Phys. Rev. C 90 (2014) 5, 055201

● Charged hadron (π/k/p) DSA in inclusive hadron production (twist-3 effect)● Y. X. Zhao et al., (Under review, Phys. Rev. C)

On-going analysis: ● Unpolarized SIDIS cross-section (Xuefei Yan, Duke University)

● Double spin asymmetry in inclusive DIS to extract g2 on 3He (Y.X. Zhao, Stony brook)

E06010 (6-GeV Transversity) Collaboration

Institutions (38) Univ. Kentucky, W&M, Duke Univ., CalTech, UIUC, Lanzhou Univ, California State Univ, Univ. Glasgow, MIT, CMU, JLab, ODU,

UVa, Hampton Univ, INFN, Mississippi State Univ, Rutgers, Kharkov Inst. of Phys. and Tech., Los Alamos National Lab, Longwood Univ, Cairo Univ, Kyungpook National Univ, China Inst. of Atomic Energy, Kent State Univ, Univ. of Sci. & Tech. of China, Florida International Univ., Univ. Massachusettes, Temple Univ, Univ. Blaise Pascal, Univ. of New Hampshire, Syracuse Univ., Yerevan Physics Inst., Univ. Ljubljana, Seoul National Univ.

Collaboration members (115) K. Allada, K. Aniol, J. R. M. Annand, T. Averett, F. Benmokhtar, W. Bertozzi, P. C. Bradshaw,

P. Bosted, A. Camsonne, M. Canan, G. D. Cates, C. Chen, J.-P. Chen, W. Chen, K. Chirapatpimol,E. Chudakov, E. Cisbani, J. C. Cornejo, F. Cusanno, M. M. Dalton, W. Deconinck, C.W. de Jager,R. De Leo, X. Deng, A. Deur, H. Ding, P. A. M. Dolph, C. Dutta, D. Dutta, L. El Fassi, S. Frullani ,J. Huang, H. Gao, F. Garibaldi, D. Gaskell, S. Gilad, R. Gilman, O. Glamazdin, S. Golge, L. Guo,D. Hamilton, O. Hansen, D.W. Higinbotham, T. Holmstrom, M. Huang, H. F. Ibrahim, M. Iodice,X. Jiang, G. Jin, M. K. Jones , J. Katich, A. Kelleher, W. Kim, A. Kolarkar, W. Korsch, J. J. LeRose,X. Li, Y. Li, R. Lindgren, N. Liyanage, E. Long, H.-J. Lu, D. J. Margaziotis, P. Markowitz, S. Marrone, D. McNulty, Z.-E. Meziani, R. Michaels, B. Moffit, C. Munoz Camacho, S. Nanda, A. Narayan, V. Nelyubin, B. Norum, Y. Oh, M. Osipenko, D. Parno, J. C. Peng, S. K. Phillips, M. Posik, A. J. R. Puckett , X. Qian, Y. Qiang, A. Rakhman, R. D. Ransome, S. Riordan, A. Saha, B. Sawatzky, E. Schulte, A. Shahinyan, M. H. Shabestari, S. Sirca, S. Stepanyan, R. Subedi, V. Sulkosky, L.-G. Tang, A. Tobias, G. M. Urciuoli, I. Vilardi, K.Wang, Y. Wang, B.Wojtsekhowski, X. Yan, X.F. Yan, H. Yao, Y. Ye, Z. Ye, L. Yuan, X. Zhan, Y. Zhang, Y.-W. Zhang, B. Zhao, Y. X. Zhao, X. Zheng, L. Zhu, X. Zhu, and X. Zong

Co-spokesperson , Graduate student, Leading Postdoc

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Summary

● Hall A Transversity experiment was very successful

● First experiment to measure the target SSA and DSA in SIDIS and inclusive hadron production channels on transversely polarized 3He

● Exploration of rich TMD physics at Jlab using polarized 3He

● 9 PhD students, including two joined after the experiment

● A total of 7 publications and few more analysis on-going

● These results laid a solid foundation for precision study of TMDs using 3He at JLab 12 GeV

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Spare Slides

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Kaon PID

Contamination of pion in kaon sample is well controlled:π+ in k+: