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

Transcription

1 Overview of Results from the Transversity Experiment (E06-010) Kalyan Allada Massachusetts Institute of Technology User Group Meeting, Jefferson Lab June 3, 2015

2 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(sqt), 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=q 2 /2M ν y=ν/ E z= Eh /ν 2

3 Transverse Momentum Dependent Quark Distributions (TMDs) Accessible through Semi-inclusive DIS reaction Unpolarized Boer-Mulders Worm-gear Transversity Polarized target Sivers Pretzelosity Polarized beam and target Helicity Worm-gear ST and SL are target polarization and λe is beam polarization 3

4 Leading Twist TMDs TMDs sensitive to transversely polarized nucleon 4

5 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) 5

6 Azimuthal Moments in SIDIS Single Spin Asymmetry

7 Azimuthal Moments in SIDIS Separate different effects through azimuthal angular dependence Collins moment Sivers moment: Pretzelosity: ST = Nucleon Spin direction ST 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)

8 Azimuthal Angular Coverage Collins angle: ɸh+ ɸs Sivers angle: ɸh- ɸs Different colors corresponds to different target spin states: left, right, up and down

9 Particle Identification BigBite BigBite +HRS K+/π+ ratio: ~5% K-/π- ratio: ~1% Pions were suppressed using Aerogel counter (A1) when selecting Kaons

10 Neutron Collins and Sivers Moments (A UT) First measurement of 3He (neutron) Transverse SSA 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) Blue band: model (fitting) uncertainties Red band: other systematic uncertainties X. Qian et al., PRL 107 (2011)

11 Global Extraction of Transversity Transversity distribution Z-B. Kang et al., arxiv: Global analysis of transversity: includes HERMES (p), COMPASS (p/d) and JLab (3He) data

12 Pretzelosity Asymmetry (AUT) Pretzelosity SSA In some relativistic quark models directly related to quark OAM h 1T=g 1 h 1 Extracted neutron moments consistent with zero within uncertainties Pretzelosity is suppressed by k2t /M2 compared to the Sivers moment Y. Zhang et al., PRC 90 (2014)

13 Beam-Target Double Spin Asymmetry (ALT) ALT 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! J. Huang et al. PRL. 108, (2012) 13

14 Collins and Sivers SSA of Kaons from 3He (neutron) Both Collins and Sivers K+ asymmetry is consistent with zero within experimental uncertainties Kaon SSA from neutron 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 Important contribution to the global kaon SSA data (others include HERMES, COMPASS on proton target) for the extraction of sea quark TMDs Y. X. Zhao, et al., Phys. Rev. C 90, (2014) Predictions from global fit M. Anselmino et al., Eur. Phys. J. A39, 89 (2009). 14

15 Transverse SSA in Inclusive Hadron Production e + 3He h+x (h = π/k/p) pt Only one hard scale : PT of the detected hadron Relevant kinematic variables: pt : Transverse momentum of hadron x F 2p L / s : pl is the long. momentum of hadron Assuming TMD factorization valid in inclusive hadron production: Sivers contribution dominates SSA Collins contribution is negligible M. Anselmino et al., Phys. Rev. D81, (2010) 15

16 Transverse SSA in Inclusive Hadron Production 3 He asymmetry ϕs= 0o ϕs= 90o AN for ϕs= 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 16

17 Transverse SSA in Inclusive Hadron Production 3 He asymmetry 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 PT>1.0 GeV) Similar behavior compared to A in pp -->hx N Neutron asymmetry K. Allada, et al. Phys. Rev. C 89, (R) 17

18 Transverse DSA in Inclusive Hadron Production e + 3He h+x (h = π/k/p) 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 g (x ) Twist-3 effects in fragmenting hadron 18

19 Transverse DSA in Inclusive Hadron Production 3 3 He asymmetry for charged pions (pt distribution) He Asymmetry for charged hadrons 19

20 Transverse DSA in Inclusive Hadron Production 3 He asymmetry 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 Neutron asymmetry Y.X.Zhao et al. arxiv: (under review in Phys. Rev. C) Predictions from K. Kanazawa et al., arxiv: (2014) 20

21 Transverse Target SSA in Inclusive DIS (A y) Upolarized beam, trasversely polarized nucleon e + 3He e' + X Target Single Spin Asymmetry: dσut µ Im (M1γ M*1γ ) is zero at Born level time-reversal invariance * dσ µ Im (M M ) is non-zero with one and two-photon interference terms UT 1γ 2γ Two parton-model predictions of two-photon exchange contributions to A y Two-photon exchange with a single quark (A. Afanasev et al.) Ay ~ 10-4, at x ~ 0.3 and Q2 ~ 2.0 GeV2 Two-photon exchange with two difference quarks (struck and spectator di-quark) Ay ~ ( A. Metz et al., and M. Schlegel et al.) HERMES proton data at Q2 > 1 GeV2 consistent with zero at ~10-3 level 21

22 Ay on Neutron from inclusive DIS Data (JLab Expt. E07-013) J. Katich et al., Phys. Rev. Lett. 113 (2014) Data from singles trigger in the BigBite and HRS First non-zero measurement of Ay (3σ). Consistent with Metz et al. using Sivers input. 22

23 Summary of Results Published Results ( ) : Charged pions SSA in semi-inclusive DIS (Collins and Sivers moments) Charged pion DSA in semi-inclusive DIS (g1t) Y. Zhang et al., Phys. Rev. C 90 (2014) 5, Charged Kaon SSA in semi-inclusive DIS (Collins and Sivers moments) K. Allada et al., Phys. Rev. C 89 (2014) (Rapid Comm.) Charged pion SSA in semi-inclusive DIS (Pretzelosity) J. Katich et al., Phys. Rev. Lett. 113 (2014) Charged hadron (π/k/p) SSA in inclusive hadron production (AN) J. Huang et al., Phys. Rev Lett. 108, (2012) SSA in inclusive DIS production (TPE) (JLab expt. E07-013) X. Qian et al., Phys. Rev. Lett. 107, (2011) Y. X. Zhao et al., Phys. Rev. C 90 (2014) 5, 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) 23

24 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 24

25 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 3 He at JLab 12 GeV 25

26 Spare Slides 26

27 Kaon PID Contamination of pion in kaon sample is well controlled: π+ in k+: <2% π- in k-: <5% 27