1 / 37

Overview of Jefferson Lab’s Spin Physics Programme

Overview of Jefferson Lab’s Spin Physics Programme. Introduction Experimental Setup Asymmetry Measurement Moments of Structure Functions Outlook. Stephen Bültmann - ODU RHIC/AGS Users Meeting, June 2007. Spin structure vs distance scale.

cormac
Download Presentation

Overview of Jefferson Lab’s Spin Physics Programme

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Overview of Jefferson Lab’s Spin Physics Programme • Introduction • Experimental Setup • Asymmetry Measurement • Moments of Structure Functions • Outlook Stephen Bültmann - ODU RHIC/AGS Users Meeting, June 2007

  2. Spin structure vs distance scale Q2 Bjorken Sum Rule Asymptotic freedom single partons multiple partons Perturbative QCD constituent quarks, N* photon interacts with pions, nucleon Chiral Perturbation Theory magnetic moment (GDH SR) GDH Sum Rule Q2=0 Stephen Bültmann - ODU RHIC/AGS Users Meeting, June 2007

  3. The CEBAF Accelerator • Electron beam • Energy up to 5.7 GeV • Current 1 - 100 µA (Hall B 50 nA) • Polarization > 0.8 Stephen Bültmann - ODU RHIC/AGS Users Meeting, June 2007

  4. Experimental Halls Hall C HMS + SOS Polarized Targets: H2 and D2 (Hall B + C) 3He (Hall A) Hall B CLAS Hall A HRS + HRS Stephen Bültmann - ODU RHIC/AGS Users Meeting, June 2007

  5. Polarized Targets in Halls B & C • Dynamically polarized targets of solid (deuterated) ammonia • 5 Tesla magnetic field • 140 GHz polarizing microwaves • 1 Kelvin superfluid helium • Longitudinal polariztion • P1 < 0.9 P1 ave = 0.7 - 0.8 • P2 < 0.4 P2 ave = 0.2 - 0.3 • measured by NMR • Also transverse polarization in Hall C • Current • 3 nA in Hall B • 100 nA in Hall C • Luminosity < 1035 cm-2 sec-1 Stephen Bültmann - ODU RHIC/AGS Users Meeting, June 2007

  6. Polarized Target in Hall A • Polarized 3He gas target • Optical pumping and spin exchange • Longitudinal and transverse polarization • P3 < 0.5 P1 ave = 0.4 • measured by NMR and EPR • Current 12 µA • Luminosity < 1036 cm-2 sec-1 Stephen Bültmann - ODU RHIC/AGS Users Meeting, June 2007

  7. CLAS Detector in Hall B Stephen Bültmann - ODU RHIC/AGS Users Meeting, June 2007

  8. k’ k k’ Elastic k q p’ q p’ xP= p xP=p P P W DIS of lepton off nucleon Virtual photon scatters off parton Stephen Bültmann - ODU RHIC/AGS Users Meeting, June 2007

  9. Kinematic Coverage EG1 EG4 Stephen Bültmann - ODU RHIC/AGS Users Meeting, June 2007

  10. Status of g1(x,Q2) • Existing data mostly for DIS and low x • Remaining • G (RHIC, COMPASS) • L (COMPASS, HERMES, Jlab) • Transversity (HERMES, Jlab, RHIC) • Large x precision measurements (Jlab) • Measurement in non-perturbative region (Jlab) Stephen Bültmann - ODU RHIC/AGS Users Meeting, June 2007

  11. Asymmetry Measurement A1 A2 e’ qe A1 A2 e the asymmetries A1 and A2 can be extracted by varying the direction of the nucleon polarization where D, , d,  are function of Q2, W, E0, R Pe Pt y nucleon the structure functions g1andg2are linear combination of A1andA2 g1(x,Q2) g2(x,Q2) Stephen Bültmann - ODU RHIC/AGS Users Meeting, June 2007

  12. Asymmetry Measurement Simultaneous extraction of A1 and A2 from measured asymmetry 1 -  E’ / E  √ Q2 A|| = D ( A1 +  A2 ) with = and D = E -  E’ 1 +  R Stephen Bültmann - ODU RHIC/AGS Users Meeting, June 2007

  13. A1+A2 for proton 1.7 GeV (proton) 5.7 GeV (proton) Parametrization of previous world data (including CLAS) by S. Kuhn , L. Stuart, et al. including “AO” and “MAID2000” for resonance region Blue solid line = Estimated contribution from A2 to A1+A2 Stephen Bültmann - ODU RHIC/AGS Users Meeting, June 2007

  14. F1 g1(x,Q2) = [(A1+´ A2)+(°-´)A2] 1+°2 g1(x,Q2) for the proton g1forthe proton Parameterization of previous world data (including CLAS) Stephen Bültmann - ODU RHIC/AGS Users Meeting, June 2007

  15. Proton/Deuteron Comparison In the ¢(1232) region and at low Q2, g1d/2 is consistent with g1p At high Q2, g1p is significantly larger than g1d/2 , indicating a negative contribution from the neutron Stephen Bültmann - ODU RHIC/AGS Users Meeting, June 2007

  16. Asymmetry Measurement • Very preliminary result • A2is larger than previously used EG1 model, basing on MAID and AO • Same result reported by RSS experiment from JLab Hall C (2007) Stephen Bültmann - ODU RHIC/AGS Users Meeting, June 2007

  17. Asymmetry Measurement in Hall C (RSS) • Polarized longitudinal and transverse ammonia target • 100 nA electron beam • Both polarizations average between 0.6 and 0.7 • HMS spectrometer at 13.5º • 160 million events Q2 range from 0.8 to 1.4 GeV2/c2 Stephen Bültmann - ODU RHIC/AGS Users Meeting, June 2007

  18. Asymmetry A1 Proton Deuteron Stephen Bültmann - ODU RHIC/AGS Users Meeting, June 2007

  19. g2 from Hall C (RSS) Twist-2 Wandzura-Wilcek approximation Stephen Bültmann - ODU RHIC/AGS Users Meeting, June 2007

  20. g2 from Hall C (RSS) Twist-3 matrix element d2 representing quark-gluon correlation d2 = 0.0057 ± 0.0009 stat. ± 0.0007 sys. for 0.29 < x < 0.84 d2 = 0.0029 at Q2 = 5 GeV2/c2 Compared to SLAC d2 = 0.0032 ± 0.0017 Stephen Bültmann - ODU RHIC/AGS Users Meeting, June 2007

  21. Polarized PDF’s • Inclusion of large amount of low-Q2 data from CLAS EG1 by Leader, Siderov, and Stamenov • Simultaneous extraction of polarized parton densities and higher twist corrections Stephen Bültmann - ODU RHIC/AGS Users Meeting, June 2007

  22. Polarized PDF’s • Error envelopes • LSS05 • LSS06 (EG1) • CLAS12 overall improved by EG1 data Stephen Bültmann - ODU RHIC/AGS Users Meeting, June 2007

  23. S11 (1535) D (1232) Global F15 (1680) Test of Quark-Hadron Duality Proton Stephen Bültmann - ODU RHIC/AGS Users Meeting, June 2007

  24. g1 from Hall C (RSS) Integration over resonance region 1.09 GeV < W < 1.91 GeV of NLO PDFs and comparison with measurement gives a ratio of 1.17 ± 0.08 Q2 range from 0.8 to 1.4 GeV2/c2 Global duality only at 2 sigma level Local duality not observed Stephen Bültmann - ODU RHIC/AGS Users Meeting, June 2007

  25. Q2 dependence of g1/F1 • Q2 dependence of g1 at fixed x is very similar to F1 in the DIS region • EG1 data show a decrease in g1/F1 even in the DIS region • Resonance region  different Q2 dependence  goes negative at  • High Q2 results agree with SLAC data Stephen Bültmann - ODU RHIC/AGS Users Meeting, June 2007

  26. Quark polarization in the valence region Assuming the naïve parton model with no sea contribution, quark polarizations in the valence region can be estimated directly from the data: ¢u/u = [5g1p-2g1d/(1-1.5wD)]/[5F1p-2F1d] ¢d/d = [8g1d/(1-1.5wD)-5g1p]/[8F1d-5F1p] ¢u /u ! 1 as x ! 1 Consistent with pQCD and QM Disagrees with SU(6) ¢d /d < 0 up to the highest x ~0.6 Consistent with Hyperfine Perturbed QM Disagrees with pQCD w/o orbital angular momentum Stephen Bültmann - ODU RHIC/AGS Users Meeting, June 2007

  27. Moments and Sum Rules QPM Ellis-Jaffe Sum Rule 3 1 4 a0 a3 + 1p = a8 + = 0.186 +QCD corr 36 36 36 3 1 4 a0 = - 0.025 +QCD corr a3 + 1n = - a8 + 36 36 36 Bjorken Sum Rule (pre QCD) Stephen Bültmann - ODU RHIC/AGS Users Meeting, June 2007

  28. 1 Q2 (GeV2) GDH Sum Rule IGDH • relates the difference of the photo-absorption cross section for helicity 1/2 and 3/2 to the nucleon magnetic moment, i.e. a connection between dynamic and static properties. Recent measurements at Bonn and Mainz, ongoing efforts at other labs • based on very general principles, as gauge invariance, dispersion relation, low energy theorem • at finite Q2 can be related to the integral of the spin structure function g1 • strong variation of nucleon spin properties as a function of Q2 G1 DIS pQCD Transition Region GDH sum rule Stephen Bültmann - ODU RHIC/AGS Users Meeting, June 2007

  29. Generalized GDH Integral A generalization of the GDH sum rule has been suggested by Ji and Osborne by relating the virtual-photon forward Compton amplitude S1to the nucleon structure function G1 X.Ji et al., Phys.Lett.B472 (2000) 1 GDH sum rule and Chiral Perturbation Theory - — + cQ2 + O (Q4) Lattice? Ellis-Jaffe Sum rule and Operator Product Expansion ~ Q2 < 0.1 GeV2 S1(0,Q2)  2 M2  x0 ò 16pa Q2 IGDH (Q2) = dx g1(x,Q2) 0.1 < Q2 < 0.5 GeV2 Q2 > 0.5 GeV2 Measurable Calculable mt(Q2) Qt-2 t=2,4,… Stephen Bültmann - ODU RHIC/AGS Users Meeting, June 2007

  30. 1 for the proton and deuteron proton deuteron 1 1 Q2(GeV2) Q2(GeV2) • Xmin=0.001, x_max= pion production threshold • shows strong Q2 dependence varying from negative to positive values as Q2 increases Stephen Bültmann - ODU RHIC/AGS Users Meeting, June 2007

  31. Low Q2 behavior of 1-PT deuteron proton preliminary preliminary Stephen Bültmann - ODU RHIC/AGS Users Meeting, June 2007

  32. EG4 projection • Extends to very low Q2 of 0.015 GeV2 both proton and deuteron • Data taken earlier this year Stephen Bültmann - ODU RHIC/AGS Users Meeting, June 2007

  33. Hall A Measurement on 3He 1n E94-110 Q2 range 0.1 - 1 GeV2 Preliminary Stephen Bültmann - ODU RHIC/AGS Users Meeting, June 2007

  34. Hall A Measurement on 3He E01-012 • g1/g2 and A1/A2 (3He/n) in resonance region, 1 < Q2 < 4 GeV2 • Study quark-hadron duality in spin structure 1n Stephen Bültmann - ODU RHIC/AGS Users Meeting, June 2007

  35. Bjorken Sum Q2 Evolution Combined data from EG1a and Hall A E94-010 A. Deur, et al., PRL 93, 212001 (2004) Stephen Bültmann - ODU RHIC/AGS Users Meeting, June 2007

  36. JLab Upgrade: EG12 projections W > 2; Q2 > 1 Allows access to higher x values Stephen Bültmann - ODU RHIC/AGS Users Meeting, June 2007

  37. Summary • A wealth of new data on the nucleon spin structure in the non-perturbative regime has been produced at Jefferson Lab as part of a broad spin physics program, still in progress • These measurements provide new information for understanding the transition between hadronic and partonic degrees of freedom by investigating spin structure functions, related sum rules and moments, asymmetries, … • A new measurement to cover the very low momentum transfer region and provide a bridge to the GDH sum rule at the photon point has just been completed recently • 12 GeV program at Jlab will offer the opportunity to extend these measurements into new kinematic regions Stephen Bültmann - ODU RHIC/AGS Users Meeting, June 2007

More Related