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Transversity Experiments at JLab Hall A

Transversity Experiments at JLab Hall A. Jian-ping Chen, Jefferson Lab On Behalf of the Jefferson Lab Hall A and Transversity Collaborations GPD2010 Workshop, Trento, Italy, Oct. 12, 2010. Introduction 6 GeV transversity experiment preliminary results on Collins/Sivers asymmetries

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Transversity Experiments at JLab Hall A

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  1. Transversity Experiments at JLab Hall A Jian-ping Chen, Jefferson Lab On Behalf of the Jefferson Lab Hall A and Transversity Collaborations GPD2010 Workshop, Trento, Italy, Oct. 12, 2010 • Introduction • 6 GeV transversity experiment • preliminary results on Collins/Sivers asymmetries • preliminary results on ALT asymmetry • Future: 12 GeV plan and EIC

  2. Introduction Why do we care about transverse structure?

  3. Nucleon (Hadron) Structure Colors are confined in hadronic system Hadron: ideal lab to study QCD Nucleon = u u d + sea + gluons Mass, charge, magnetic moment, spin, axial charge, tensor charge Decomposition of each of the above fundamental quantities Mass: ~1 GeV, but u/d quark mass only a few MeV each! Momentum: total quarks only carry ~ 50% Spin: ½, total quarks contribution only ~30% Spin Sum Rule Orbital Angular Momentum Relations to GPDs and TMDs Tensor charge Transverse sum rule? Partons and gluon field are in-separable Multi-parton correlations are important Beyond co-linear factorization Multi-dimensional structure and distributions Transverse dimension is crucial for complete understanding of nucleon structure and QCD, and help shed light in understanding confinement

  4. Four Decades of Nucleon Structure Study • 1970s: SLAC DIS  Bjorken Scaling, discovery of partons (quarks) 4 decades study on unpolarized structure, 5 orders in x range and Q2 Global analyses to extract unpolarized PDFs • 1980s: ‘spin crisis’, quark spin contribution to proton spin is very small 3 decades study on longitudinally polarized structure: 3 orders in x and 2 in Q2 • DS ~ 30%; DG small Orbital angular momentum important, definition? A+=0 (light-cone) gauge(½)DS + Lq+ DG + Lg=1/2 (Jaffe) Gauge invariant (½)DS + Lq + JG =1/2 (Ji) A new decomposition (X. Chen, et. al.) • 2000s:Transversity and Transverse-Momentum Dependent Distributions Model-dependent extraction of transversity distributions Spin-orbit correlations, orbital angular momentum Multi-dimension structure Multi-parton correlations, QCD dynamics Confinement

  5. Current Status on Transversity and TMDs What have we learned?

  6. Transversity and TMDs • Three twist-2 quark distributions: • Momentum distributions: q(x,Q2) = q↑(x) + q↓(x) • Longitudinal spin distributions: Δq(x,Q2) = q↑(x) - q↓(x) • Transversity distributions: δq(x,Q2) = q┴(x) - q┬(x) • It takes two chiral-odd objects to measure transversity • Semi-inclusive DIS Chiral-odd distributions function(transversity) Chiral-odd fragmentation function(Collins function) • TMDs: (without integrating over PT) • Distribution functions depends on x, k┴ and Q2 : δq, f1T┴ (x,k┴,Q2), … • Fragmentation functions depends on z, p┴ and Q2 : D, H1(x,p┴,Q2) • Measured asymmetries depends on x, z, P┴ and Q2 : Collins, Sivers, … (k┴, p┴ and P┴ are related)

  7. “Leading-Twist” TMD Quark Distributions Nucleon Unpol. Trans. Long. Quark Unpol. Long. Trans.

  8. Wpu(k,rT) “Mother” Wigner distributions d2kT d2rT GPDs/IPDs H(x,rT),E(x,rT),.. TMDs f1u(x,kT), .. h1u(x,kT) d2kT Multi-dimensional Distributions quark polarization d2rT PDFs f1u(x), .. h1u(x) • Gauge invariant definition (Belitsky,Ji,Yuan 2003) • Universality of kT-dependent PDFs (Collins,Metz 2003) • Factorization for small kT. (Ji,Ma,Yuan 2005)

  9. BNL FNAL lepton lepton proton lepton JPARC pion proton antilepton Drell-Yan electron pion positron pion e–e+ to pions Access TMDs through Hard Processes EIC proton SIDIS Partonic scattering amplitude Fragmentation amplitude Distribution amplitude

  10. Separation of Collins, Sivers and pretzelocity effects through angular dependence in SIDIS

  11. AUTsin() from transv. pol. H target `Collins‘ moments `Sivers‘ moments • Sivers function nonzero (p+) • orbital angular momentum ofquarks • Regular flagmentation functions • Non-zero Collins asymmetry • Assume dq(x) from model, then • H1_unfav ~ -H1_fav • H1from Belle (arXiv:0805:2975)

  12. Collins/Sivers asymmetries from COMPASS deuteron Phys. Lett. B 673 (2009) 127-135 u and d cancellation?

  13. Transversity Distributions A global fit to the HERMES p, COMPASS d and BELLE e+e- data by the Torino group (Anselmino et al.). PRD 75, 054032 (2007)

  14. Collins/Sivers Moments for Kaon S. Gliske’s talk at DNP09

  15. Other TMDs COMPASS 2002-2004 arXiv:0705.2402 Pretzelocity g1T xB

  16. Summary of Current Status Large single spin asymmetry in pp->pX 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)? - consistent with 0 for the deuteron (COMPASS) Sivers Asymmetries - non-zero for p+ from proton (HERMES), smaller with COMPASS data? - consistent with zero for p- from proton and for all channels from deuteron - large for K+? Collins Fragmentation from Belle Global Fits/models by Anselmino et al., Yuan et al. and … Very active theoretical and experimental study RHIC-spin, JLab (6 GeV and 12 GeV), Belle, FAIR, J-PARC, … EIC

  17. 6 GeV Transversity Experiment: E06-010 Preliminary Results

  18. E06-010 Overview • First measurement of the SSA and DSA in SIDIS • Major installation/upgrade • 3He Target, BigBite Electron Package, LHRS RICH • Successful data taking from Oct 08 to Feb 09 • Spokespersons Xiaodong Jiang (Los Alamos), Jian-ping Chen (JLab), Evaristo Cisbani (INFN-Rome), Haiyan Gao (Duke), Jen-Chieh Peng (UIUC) • 7 PhD Thesis Students • K. Allada (Kentucky), C. Dutta (Kentucky), X. Qian (Duke), graduated in May, 2010; J. Katich (W&M), graduated in Sept. 2010. • J. Huang (MIT), Y. Wang (UIUC), Y. Zhang (Lanzhou)

  19. E06‑010 Experiment Setup Luminosity Monitor • Polarized 3He Target • Polarized Electron Beam • ~80% Polarization • Fast Flipping at 30Hz • PPMLevel Charge Asymmetry controlled by online feed back • BigBite at 30º as Electron Arm • Pe = 0.7 ~ 2.2 GeV/c • HRSL at 16º as Hadron Arm • Ph = 2.35 GeV/c Beam Polarimetry (Møller + Compton)

  20. JLab polarized 3He target • longitudinal, transverse and vertical • Luminosity=1036 (1/s) (highest in the world) • High in-beam polarization ~ 65% • Effective polarized neutron target • 13 completed experiments 6 approved with 12 GeV (A/C) 15 uA

  21. Performance of 3He Target • High luminosity: L(n) = 1036 cm-2 s-1 • Record high 65% polarization (preliminary) in beam with automatic spin flip / 20min

  22. BigBite Spectrometer Pre-Shower Shower • Single Dipole Magnet • Detects electrons • A “big bite” of acceptance • DW = 64 msr • P : 0.7 ~ 2.2 GeV/c • 3 Wire Chambers: 18 planes for precise tracking • Bipolar momentum reconstruction • Pre-Shower and Shower for electron PID • Scintillator for coincidence with Left HRS Scintillators 3 Multi-wire Drift Chambers (18 planes)

  23. J.P. Chen, USTC, 2007

  24. High Resolution Spectrometer • Left HRS to detect hadrons of ph = 2.35 GeV/c • QQDQ magnet configuration • Very high momentum resolution • Vertical Drift Chambers • Tracking • Scintillator trigger planes • 340ps Coinc. Timing Resolution • Gas Cherenkov & Lead-glass blocks • e/hadron separation • Aerogel Cherenkov &RICH detector • π/K separation Detector Package Detector Hut Q1 Q2 D1 Q3

  25. J.P. Chen, USTC, 2007

  26. x bin 1 2 3 4 Data Coverage x bin 2 x bin 1 Q2>1GeV2 Kinematics Coverage pT& ϕh- ϕS Coverage W>2.3GeV x bin 3 x bin 4 z=0.4~0.6 W’>1.6GeV

  27. Analysis Progress • 7 PhD Students • 3 graduated in May; 1 in Sept., 2010. • Extensive data quality checks and systematic study -- Run selection/beam trip cut/yield check/witness channel • Two analysis teams cross check results • Red Team: Maximum Likelihood Method • Blue Team: Local Pair-Angular Bin-Fit Method • Results are consistent • Radiative corrections not done yet • Systematics are being further checked

  28. Asymmetry Extraction • It’s not simple! • Spin flip/angular coverage/kinematics dependence • Two analysis team • Independent method/code/compare results • Blue Team • local pair-angular bin-fit method • Low bias from yield drift • ideal for pion spin asymmetry extraction • Red Team • Maximum Likelihood method • Stable at low statistic/capable of high dimensional fit

  29. Result Comparison • Both asymmetry and modulation cross checked • Results are consistent E06010 RAW Asym. Preliminary

  30. Preliminary Asymmetry ALT Result • Preliminary 3He ALT - Systematic uncertainty is still under work - Projected neutron ALT stat. uncertainty : 6~10% To leading twist:

  31. Summary on 6 GeVTransversity Experiment • First measurement of angular modulated SSA and DSA in neutron (3He) SIDIS • Data cover valence range • Preliminary Results • In progress: • Simulation (coincidence ) • Systematics (further check) • Neutron asymmetry extraction • Kaon asymmetries • Submitting first paper in few months

  32. Future: 12 GeV with SOLID Precision 4-d mapping

  33. Precision Study of Transversity and TMDs From exploration to precision study Transversity: fundamental PDFs, tensor charge TMDs provide 3-d structure information of the nucleon Learn about 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

  34. Solenoid detector for SIDIS at 11 GeV Yoke Y[cm] Coil 3He Target FGEMx4 Aerogel Gas Cherenkov LGEMx4 LS HG SH GEMx2 PS Z[cm]

  35. 4-d Mapping of Collins/Sivers Asymmetries 12 GeV With SOLID (L=1036) • Both p+ and p- • For one z bin (0.5-0.55) • Will obtain 8 z bins (0.3-0.7) • Upgraded PID for K+ and K-

  36. Power of SOLID

  37. Discussion Unprecedented precision 4-d mapping of SSA Collins and Sivers p+, p- and K+, K- Study factorization with x and z-dependences Study PT dependence With similar quality SIDIS data on the proton and data from e+e- extract transversity and fragmentation functions for both u and d quarks determine tensor charge study TMDs for valence quarks study quark orbital angular momentum Combining with world data, especially data from high energy facilities (future EIC) study Q2 evolution (need theoretical development) sea and gluon TMDs (more surprises are waiting?) Global efforts (experimentalists and theorists), global analysis Precision information on multi-dimension nucleon structure

  38. Future: EIC From Valence Quarks to Sea and Gluons

  39. EIC phase space 12 GeV: from approved SoLID SIDIS experiment Lower y cut, more overlap with 12 GeV 0.05 < y < 0.8

  40. EIC projection: Proton π+ (z = 0.3-0.7)

  41. Summary Why transverse dimension? Complete understanding of nucleon structure Transverse momentum dependence - strong quark-gluon correlations Key to understanding QCD in all regions, including confinement region What have we learned? Non-zero Collins and Sivers asymmetries for pions and Kaons Non-favored Collins fragmentation functions as important as favored ones Model dependent extractions of transversity, Sivers and Collins functions Preliminary results from 6 GeV neutron transversity experiment First measurements of Collins ,Sivers, ALT asymmetries on the neutron Important inputs for global analysis Constraints on d-quark distributions Future12 GeV measurements with SOLID and EIC? Precision 4-d (x,z,PT, Q2)mapping of TMDs Ultimate coverage in kinematics, complete 4-d (x,z,PT,Q2) mapping Lead to breakthroughs in full understanding of nucleon structure and QCD

  42. Strong Interaction and QCD • Strong interaction, running coupling ~1 -- QCD: accepted theory for strong interaction -- asymptotic freedom (2004 Nobel) perturbation calculation works at high energy -- interaction significant at intermediate energy quark-gluon correlations -- interaction strong at low energy (nucleon size) confinement • theoretical tools: pQCD, OPE, Lattice QCD, AdS/CFT, … • A major challenge in fundamental physics: Understand QCD in all regions, including strong (confinement) region as E

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