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The Hall A Neutron Transversity Experiment

The Hall A Neutron Transversity Experiment. Andrew Puckett, LANL (JLab Hall A/E06-010 Collaborations) Presented to the Hall A Collaboration Meeting 6/9 /2011 . Outline. Introduction: brief review of SIDIS formalism, transverse SSA physics Status of transverse SSAs and TMDs in SIDIS

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The Hall A Neutron Transversity Experiment

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  1. The Hall A Neutron Transversity Experiment Andrew Puckett, LANL (JLab Hall A/E06-010 Collaborations) Presented to the Hall A Collaboration Meeting 6/9/2011

  2. Outline • Introduction: brief review of SIDIS formalism, transverse SSA physics • Status of transverse SSAs and TMDs in SIDIS • Status of JLab/Hall A experiment E06-010: neutron transversity • Final results and discussion of the data • Conclusions Hall A Collaboration Meeting

  3. Semi-Inclusive Deep Inelastic Scattering • In addition to usual DIS observables, SIDIS reaction N(e,e’h)X provides access to: • quark flavor • quark transverse motion • quark transverse spin • Extra degrees of freedom relative to inclusive DIS  more numerous and complicated structure functions • TMD approach: beyond collinear factorization, 8 leading-twist TMDs Hall A Collaboration Meeting

  4. SIDIS Kinematic Definitions • Incident (scattered) lepton four-momentum: l = (E,k), l’ = (E’,k’) • Scattered hadron four-momentum Ph = (Eh, ph) • Azimuthal angles defined according to Trento convention (right) Hall A Collaboration Meeting

  5. Transverse Single-Spin Asymmetries Large left-right single-spin asymmetry (SSA) first observed in inclusive pion production in pp collisions. SSA in naive parton model approach ~ αSmq/Q; could not be reconciled with this observation FNAL E704: PLB 264, 462 (1991) Hall A Collaboration Meeting

  6. Transverse SSAs in SIDIS • Transverse target spin-dependent cross section for SIDIS • Collins effect—chiral-odd quark transversity DF; chiral-odd Collins FF • Sivers effect—access to quark OAM and QCD FSI mechanism • “Pretzelosity” or Mulders-Tangerman function—access to wavefunction components differing by 2 units of OAM Different TMD contributions isolated via azimuthal modulations Hall A Collaboration Meeting

  7. Physics of Transverse SSAs—Sivers Effect • Sivers function is a correlation between kT of unpolarized quarks and nucleon transverse spin; • Connected to quark OAM • Generates left-right asymmetry in the SIDIS cross section (polarization normal to hadron production plane): • Naive T-odd: presence requires a phase; generated (in SIDIS) by QCD FSI (Brodsky, Hwang, Schmidt) • Based on gauge invariance, QCD predicts sign change of Sivers function between SIDIS and Drell-Yan production • Needs experimental verification! • Crucial test for TMD factorization approach to SSAs Hall A Collaboration Meeting

  8. Physics of Transverse SSAs—Collins Effect • Transversity distribution expresses the correlation between quark and nucleon transverse polarization. • Accessible in SIDIS by coupling to spin-dependent Collins fragmentation function: • Gluon transversity vanishes due to helicity conservation quark transversity is “valence-like” • Soffer bound: • For non-relativistic quarks, h1 = g1, difference between helicity and transversity is a signature of relativistic effects • First moment of h1 = tensor charge; calculable in lattice QCD Hall A Collaboration Meeting

  9. Transversity and Collins FFs from SIDIS and e+e- Data u and d quark transversity Favored/Unfavored Collins FFs • NPB 191, 98 (2009): Phenomenological global fit of quark transversity distributions and Collins FFs to latest HERMES proton + COMPASS deuteron SIDIS data and BELLE e+e- data • Data favor opposite sign u and d quark transversity, constraints from pre-2007 data are limited • Latest fit favors h1d close to Soffer limit. Hall A Collaboration Meeting

  10. Sivers Functions from SIDIS Data • EPJ A, 39, 89 (2009) • Extraction and flavor separation of Sivers functions for all light-quark/antiquark flavors using phenomenological ansatz • u and d quark Sivers of opposite sign, similar magnitude • Large K+ Sivers moments appear to require a positive anti-s Sivers function • ubar, s, not presently distinguishable from zero • Negative dbar favored Hall A Collaboration Meeting

  11. E06-010 in Jefferson Lab Hall A Institutions CMU, Cal-State LA, Duke, Florida International, Hampton, UIUC, JLab, Kharkov, Kentucky, Kent State, Kyungpook National South Korea, LANL, Lanzhou Univ. China, Longwood Univ. Umass, Mississippi State, MIT, UNH, ODU, Rutgers, Syracuse, Temple, UVa, William & Mary, Univ. Sciences & Tech China, Inst. of Atomic Energy China, Seoul National South Korea, Glasgow, INFN Roma and Univ. Bari Italy, Univ. Blaise Pascal France, Univ. of Ljubljana Slovenia, Yerevan Physics Institute Armenia. Collaboration members 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 (Co-SP), W. Chen, K. Chirapatpimol, E. Chudakov, , E. Cisbani(Co-SP), J. C. Cornejo, F. Cusanno, M. Dalton, W. Deconinck, C. de Jager, R. De Leo, X. Deng, A. Deur, H. Ding, C. Dutta, C. Dutta, D. Dutta, L. El Fassi, S. Frullani, H. Gao(Co-SP), F. Garibaldi, D. Gaskell, S. Gilad, R. Gilman, O. Glamazdin, S. Golge, L. Guo, D. Hamilton, O. Hansen, D.W. Higinbotham, T. Holmstrom, J. Huang, M. Huang, H. Ibrahim, M. Iodice, X. Jiang (Co-SP), G. Jin, M. Jones, J. Katich, A. Kelleher, 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(Co-SP), S. K. Phillips, M. Posik, A. Puckett, X. Qian, Y. Qiang, A. Rakhman, R. Ransome, S. Riordan, A. Saha, B. Sawatzky,E. Schulte, A. Shahinyan, M. 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, H. Yao, Y. Ye, Z. Ye, L. Yuan, X. Zhan, Y. Zhang, Y.-W. Zhang, B. Zhao, X. Zheng, L. Zhu, X. Zhu, X. Zong. Ph.D. thesis students, Co-spokespersons Hall A Collaboration Meeting

  12. Experiment Setup • 3He(e,e’π±)X in JLab Hall A • Transversely polarized 3He target through spin-exchange optical pumping of hybrid-alkali (Rb-K) mixture. • World record polarized 3He figure-of-merit: ~60% average polarization @ 12 μA avg. beam current • Electrons in BigBite spectrometer at 30° • Hadrons in High Resolution Spectrometer (HRS) at 16° Luminosity Monitor Beam Polarimetry (Møller + Compton) Hall A Collaboration Meeting

  13. Polarized 3He Target ~87% ~8% ~1.5% Polarized 3He as effective polarized neutron target ~10 atm 3He = ~1036 cm-2s-1 en luminosity Final target chamber <P> = (55.4 ± 2.8)% Effective nucleon polarization approach: Scopetta, PRD 75, 054005 (2007) Hall A Collaboration Meeting

  14. BigBite Spectrometer • 1.2 Tesla dipole magnet in front of detector stack • Positioned to subtend ~64 msr solid angle • Large out-of-plane angle acceptance (~±240 mrad), essential to maximize ϕ coverage, separate Collins/Sivers effects • Three drift chambers for tracking • Shower+Preshower for electron PID • Scintillator for timing BigBite Spectrometer Hall A Collaboration Meeting

  15. High Resolution Spectrometer Detector Package Detector Hut • Gas Cherenkov+Lead-glass for e/π separation • Coincidence Vertex + TOF w/ Bigbite suppress random coinc. • Aerogel+RICH+TOF: π/K separation >10:1 K rejection factor Q1 Q2 D1 Q3 Hall A Collaboration Meeting

  16. Kinematic and Azimuthal Coverage z pT π+ π- z, pT for different x bins, π± Collins Sivers Q2, W, z, W’ vs. x Collins/Sivers angle coverage, x bins 1-4, different target spin states Hall A Collaboration Meeting

  17. Analysis Highlights Hall A Collaboration Meeting

  18. Analysis: Target Single-Spin Asymmetry Target single-spin asymmetry from normalized yields, need to consider : beam charge, target density, DAQ life time, detector efficiency etc. 2845 target spin “local pairs” Automatic target spin flip once every 20 minutes. Beam Charge + vs Beam Charge - Beam charges are well-balanced between the pairs Hall A Collaboration Meeting

  19. SSA check: HRS single-arm3He SSA(Witness channels on 3He, not corrected for target polarization and dilution) K. Allada Univ. of Kentucky 2010. False asymmetry < 0.1% Hall A Collaboration Meeting

  20. Results—3He Collins+Sivers Moments • 3He π± Collins/Sivers moments <5% asymmetry magnitude • Collins consistent with zero, except at highest x, >2.3σ below zero • π+ Sivers moments favor negative values • Systematics: • “Experimental” includes contamination/dilution/acceptance/target density/yield drift/etc... • “Fit” results from neglecting other allowed azimuthal modulations of the SIDIS cross section PRELIMINARY E06-010 Results, 3He Draft publication submitted to PRL! Hall A Collaboration Meeting

  21. Comparison with World Data Hall A Collaboration Meeting

  22. Results—Neutron Collins/Sivers Moments • Neutron extracted from 3He using: • Nucleon effective polarization • Proton dilution from measured cross-section ratio of 1H2/3He • FSI: spin-independent(spin-dependent) estimated at <3.5 (dilution)% (<1% (asymmetry)) • Results compared to: • Global fit prediction • quark/diquark model (DQM): PRD 83, 037502 (2011) • Light-cone quark model (LCQM): PRD 79, 094012 (2009) and PRD 78, 034025 (2008) PRELIMINARY E06-010 results, neutron Draft publication submitted to PRL! Hall A Collaboration Meeting

  23. Best Neutron Measurements at High x Hall A Collaboration Meeting

  24. Paper posted on arxiv:1106.0363Submitted to PRL Hall A Collaboration Meeting

  25. 3He double-spin asymmetry ALT Preliminary • First observation of a non-zero ALT. • First measurement on neutron(3He). • Relate to quark TMD g1T(x, kT). • The real part of quark L=0✖L=1 interference, “twin-brother” of Sivers. Ph.D. thesis of J. Huang (MIT 2011). down-quark’s g1T(x) is rather small at low-x, negative at high-x. up-quark’s g1T(x) is not small, positive in sign. ALT on proton should be noticeable. Hall A Collaboration Meeting

  26. Status of Ongoing Efforts • Detailed results/kinematics tables, plots: • https://hallaweb.jlab.org/experiment/transversity/E06010/ • Long analysis note (in progress): • http://www.jlab.org/~kalyan/longnote/ • ALT paper drafted, under revision in core analysis group • Long paper drafting started • Inclusive (e,e’) and inclusive hadron (e,h) asymmetries • Kaon results Hall A Collaboration Meeting

  27. Conclusions • Successful execution and data analysis of E06-010, results submitted to PRL • Best measurement of neutron Collins/Sivers moments in the valence quark region • Largely consistent with expectations from HERMES/COMPASS data • Laid the foundation for high-precision neutron TMD measurements in multi-dimensional kinematic coverage @ JLab 12 GeV. Hall A Collaboration Meeting

  28. backup slides Hall A Collaboration Meeting

  29. Nature of E06-010 Results, I E06-010 n(e,e’π+)X Sivers result strongly suggests d quark Sivers < 0, consistent with expectation from HERMES+COMPASS fit Down quark dominates n(e,e’π+)X cross section Hall A Collaboration Meeting

  30. Nature of E06-010 Results, II • Updated transversity and Collins FF fit: arXiv:0812.4366v1 to include new data from HERMES/COMPASS • Soffer bound enforced in model/fitting; • Current fit favors a result bumping up against the Soffer bound for d-quark transversity. • Small Collins moments predicted for n(e,e’π±)X due mainly to Soffer bound • High-x neutron π+ Collins moment tantalizingly large; a violation? But more precision needed to conclude anything... ? arXiv:0812.4366v1 Hall A Collaboration Meeting

  31. BigBite Performance: I • Vertex calibration using multi-foil Carbon target: • Vertex resolution: ~7 mm • Angle calibration using sieve slit: • Angular resolution: <10 mr BigBite Sieve Slit Hall A Collaboration Meeting

  32. BigBite Performance, II PID using preshower/shower: π- contamination <2% Momentum calibration using 1H(e,e’p) at two beam energies: Resolution dp/p ~1% Hall A Collaboration Meeting

  33. Neutron Double-Spin Asymmetry ALT • ∝ Worm-gear TMD, g1T ⊗ D1 • Dominated by L=0 (S) and L=1 (P) interference. • Consist with model in sign.suggest a larger asymmetry. Preliminary Hall A Collaboration Meeting

  34. SIMC: E06-010 Monte Carlo Test bias and efficiency of MLE method at E06-010 statistics Successful asymmetry extraction from simulated data Hall A Collaboration Meeting

  35. NSAC Milestone 2010-2015: HP13“Test unique QCD predictions for relations between single-spin phenomena in p-p scattering and those observed in deep-inelastic scattering”. Estimated statistical uncertainties of 3-year running at FNAL following E906 • A new 10 cm long vertically polarized NH3 target. PT=0.80. • Frequent target spin flip to reduce systematic uncertainties. Hall A Collaboration Meeting

  36. Layout of experiment • Electron arm (BigBite) at 30° • Hadron arm (SBS) at 14° • Upgraded high-luminosity 3He target, 60 cm long; target spin can be oriented in 8 transverse directions • 10X larger angular acceptance compared to 6 GeV transversity • BigBite effective solid angle for 60 cm target = 45 msr; ~5/1 vertical/horizontal aspect ratio • SBS solid angle = 50 msr; 4/1 vertical/horizontal aspect ratio • “Super-Big” momentum bite for h arm: 2 GeV < ph < full beam energy Hall A Collaboration Meeting

  37. Impact of E06-010 Results on World Data E06-010 3He and COMPASS p/d E06-010 n vs COMPASS d-p • E06-010 Helium-3 results are comparable in precision and complementary in x coverage (high-x/valence region) compared to COMPASS p/d • E06-010 neutron results provide the best constraint on neutron Sivers moments in the valence region, and comparable to COMPASS for neutron Collins moments after correcting for kinematic suppression Dnn Hall A Collaboration Meeting

  38. Hadron arm: Super BigBite Spectrometer (SBS) • http://hallaweb.jlab.org/12GeV/SuperBigBite/ • Warm dipole magnet 48D48, Bdl = 2 Tm; cut in yoke for passage of beam pipe, reach to very forward angles. (Lambertson magnet, familiar concept in accelerator physics). • Detectors for SIDIS • GEMs: high-rate capability, high-resolution tracking; momentum/angle/vertex/RICH, resolution • HCAL: Iron-scint hadronic calorimeter; trigger + timing + coordinate measurement+reduce search area for high-rate tracking • HERMES RICH: Hadron PID, full π/K/p separation 2 GeV<p<15 GeV Hall A Collaboration Meeting

  39. Charge Tagger = GEM with pad readout • Electron arm: BigBite Spectrometer • Already used successfully in a large number of experiments, including E06-010 (transversity) • Detectors for SIDIS • Lead-glass preshower/shower for trigger and offline pion rejection; threshold = 1 GeV • GEM chambers (INFN) instead of MWDC: • Increase rate capability in high-luminosity environment • Improve resolution • Gas Cherenkov: trigger and pion rejection [experience in hand, planned improvements] • Charge tagger: possible supplement to GC for neutral trigger suppression Hall A Collaboration Meeting

  40. High Luminosity Polarized 3He Target • History of FOM increases in JLab polarized 3He experiments (top right) • New design with convection-driven flow • Fast replacement of polarized gas • Tolerate higher beam currents—support up to 60 μA, 60 cm long cell • Decouple location of target chamber and pumping chamber; decouple magnetic field directions • Concept already demonstrated in bench tests • Fast spin orientation: ~every 2 minutes • Metal target cell in vacuum: reduce non-3He material on beamline—reduce background rates Bench test of convection flow Schematic of target chamber in vacuum Hall A Collaboration Meeting

  41. Hall A Collaboration Meeting

  42. SOLID: Solenoid Detector for TMD Studies Hall A Collaboration Meeting

  43. Inclusive DIS and PDFs MSTW2008 NNLO PDFs: arXiv:0901.0002v3 • Deep-inelastic lepton-nucleon scattering N(e,e’)X (DIS) is the richest source of information on nucleon structure • Greatest triumph of pQCD; factorization, universality, scale evolution of PDFs HERA F2p arXiv:hep-ex/0211051v1 Hall A Collaboration Meeting

  44. Polarized DIS and Helicity PDFs PDG2010 compilation of g1 data DSSV NLO global fit: PRD 80, 034030 (2009) Hall A Collaboration Meeting

  45. Physics of transverse target SSA Collins Effect Sivers Effect Correlation between quark transverse momentum and nucleon transverse spin “Naive T-odd”—presence requires interference between S-wave and P-wave light-cone WF components In SIDIS: QCD FSI between struck quark and target remnant generates required phase. In Drell-Yan: QCD ISI between active partons and spectator nucleons Fundamental QCD prediction (based on gauge invariance): • Transversity distribution; correlation of transverse quark/nucleon polarization. • First moment = tensor charge; test of lattice QCD prediction • Chiral-odd; access in SIDIS combined with chiral-odd Collins FF. Strongly suppressed in inclusive DIS • Soffer bound: Hall A Collaboration Meeting

  46. Status of Experimental Data: Transverse Target SSAs in SIDIS Hall A Collaboration Meeting

  47. HERMES: Sivers Effect in Proton SIDIS • Sivers moments in e± SIDIS on transversely polarized protons (HERMES Collaboration): • PRL 103, 152002 (2009) • Key observations: • π+/K+ Sivers moments “large” and positive • π-/K- ≈ 0 • Suggests strong flavor dependence; partial cancellation between u and d quark Sivers functions. • Increases with transverse momentum pT; “saturation” above 0.4 GeV. Hall A Collaboration Meeting

  48. COMPASS: Sivers Effect in Deuteron SIDIS • COMPASS Collaboration: Sivers moments in muon SIDIS on transversely polarized deuterons: • PLB 673, 127 (2009) • COMPASS deuteron Sivers data for all measured hadron species ~0; • Combined with HERMES proton data, suggest a cancellation between proton and neutron; u/d quarks Hall A Collaboration Meeting

  49. HERMES: Collins Effect in Proton SIDIS • Collins moments in e± SIDIS on transversely polarized protons: • PLB 693, 11 (2010) • Positive asymmetries for π+ and K+ • Negative asymmetries for π- • K- ~ 0 • “Unfavored” Collins FF could be comparable to “favored” based on similar size of π+/π- asymmetries (consistent with BELLE e+e- annihilation data: PRL 96, 232002 (2006) ) Hall A Collaboration Meeting

  50. COMPASS: Collins Effect in Deuteron SIDIS • Collins effect in muon SIDIS on transversely polarized deuterons: • PLB 673, 127 (2009) • All asymmetries compatible with zero; as in Sivers case, suggesting a cancellation between p/n and u/d quarks Hall A Collaboration Meeting

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