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Studies of Spin-Orbit Correlations at JLab

Studies of Spin-Orbit Correlations at JLab. P. Bosted, H. Avakian. Trento, Italy , May 2007. Outline. Semi-inclusive processes Factorization Studies at JLab at 6 GeV (HALL-C,CLAS) Spin Orbit Correlations Unpolarized Target Polarized Target Summary. Semi-inclusive DIS. pion.

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Studies of Spin-Orbit Correlations at JLab

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  1. Studies of Spin-Orbit Correlations at JLab P. Bosted, H. Avakian Trento, Italy, May 2007

  2. Outline • Semi-inclusive processes • Factorization Studies at JLab at 6 GeV (HALL-C,CLAS) • Spin Orbit Correlations • Unpolarized Target • Polarized Target • Summary

  3. Semi-inclusive DIS pion Main focus of SIDIS studies: MX • orbital motion of quarks (pt, f dependence) • parton distributions (separate valence, sea) X.Ji • Where region I/II boundary? • Can useful information come from Region II?

  4. SIDIS kinematic plane and relevant variables pion MX Pt is transverse momentum relative to virtual photon W2=M2+Q2(1/x-1) is invariant mass of total hadronic final state

  5. Unpolarized target e p Longitudinally pol. target Transversely pol. target e p Do we understand well the helicity distributions? SIDIS (g*p→pX) cross section at leading twist (Ji et al.) e Boer-Mulders 1998 Kotzinian-Mulders 1996 Collins-1993 structure functions = pdf × fragm × hard × soft (all universal) To observe the transverse polarization of quarks in SIDIS spin dependent fragmentation is required!

  6. Factorzation in SIDIS Basic idea: hit a single quark in nucleon which then hadronizes into a jet with negligible interaction with remenant quarks. s(x,z,PT) =? PDF(x,kt) x Frag.Fun.(z,pt) Example, SIDIS p+ from u quark in proton sp+(x,z,ph) =? u(x,kt) x D+(z,pt) When integrated over transverse momenta of quarks and hadrons

  7. EXPERIMENT E00-108 at JLAB Halll C • Unpolarized electrons E=6 GeV • Scattered electrons E’=1.6 GeV, 25 to 40 deg. Average Q2 2.5 GeV2. • W about 2.5 GeV, but Mx<2 GeV. • Detected positive and negative pions near 12 degrees • Proton and deuteron targets • Made scans in x, z. pt<0.2 GeV

  8. Z-Dependence of cross sections Good agreement with prediction using CTEQ5M PDFs and Binnewies fragmentation functions, except for z>0.7, or Mx>1.4 GeV. D or D+,D- X=0.3, Q2=2.5 GeV2, W=2.5 GeV

  9. In more detail, form super-ratios Simple LO picture in valence region: sp(p+) = 4u(x)D+(z) + d(x)D-(z) sp(p-) = 4u(x)D-(z) + d(x)D+(z) sd(p+) = [u(x)+d(x)] [4D+(z) + D-(z)] sd(p-) = [u(x)+d(x)] [4D-(z) + D+(z)] Rpd+= [sp(p+) + sp(p-)] / [sd(p+) + sd(p-)] = [4u(x) + d(x)] / 5[u(x)+d(x)] = sp(x)/sd(x) for any z, x, pt (if d and u have same pt depdendence)!

  10. In more detail, form super-ratios Simple LO picture in valence region: sp(p+) = 4u(x)D+(z) + d(x)D-(z) sp(p-) = 4u(x)D-(z) + d(x)D+(z) sd(p+) = [u(x)+d(x)] [4D+(z) + D-(z)] sd(p-) = [u(x)+d(x)] [4D-(z) + D+(z)] Rpd-= [sp(p+) - sp(p-)] / [sd(p+) - sd(p-)] = [4uv(x) - dv(x)] / 3[uv(x)+dv(x)] for any z, x!

  11. Rpd+ Rpd- Both ratios agree PDF models for z<0.7 (Mx>1.4 GeV)

  12. Another test: D-/D+ from Deuteron p+ to p- ratio Results agree HERMES and EMC for z=0.55 and x>0.35. Maybe some x depdendence x<0.35 (sea quark correction?)

  13. Now look at transverse momentum dependence • Previous plots all for pion transverse momentum Ptp<0.1 GeV • Looks like factorization works for 0.3<z<0.7, 0.2<x<0.5, Q2=2.5 GeV2. • Publsihed in Phys. Rev. Lett. 98, 022001 (2007) • Ptp probes combination of quark intrinsitc momentum kt and favored and unfavored fragmentation widths pt (not necessarily same)

  14. Another test: D-/D+ from Deuteron p+ to p- ratio Ratio of fragmentation functions appears independent of hadron transverse momentum at these kinematics (x=0.3, Q2=2.5, z=0.55)

  15. Unpolarized target azimuthal asymmetries EMC(280GeV m) CLAS@5.7 M.Osipenko ep+X CLAS 5.7 GeV (preliminary) • Significant cosf,cos2f observed at large PT with CLAS at 5.7 GeV allow studies of flavor dependence of quark transverse momentum distributions.

  16. Unpolarized target azimuthal asymmetries M.Osipenko 5 fold x-section extracted Integrated over f and PT z-dependence extracted H2 (squares after mass corrections) consistent with NLO calculations (red line).

  17. Significant cos,cos2 moments observed at CLAS • <cos2f> negative at small PT • <cos2f> shows week Q2 dependence CLAS PRELIMINARY Unpolarized target azimuthal asymmetries M.Osipenko <cosf> <cos2f> • Significant cosf,cos2f observed at large PT with CLAS at 5.7 GeV cos2f moment consistent with the sign of Boer-Mulders contribution at small PT

  18. Polarized SIDIS at JLAB using CLAS Scattering of 5.7 GeV polarized electrons off polarized NH3, ND3 • ~8M p+ in DIS kinematics, Q2>1 GeV2, W2>4 GeV2, y<0.85, z>0.5 • beam polarization 73% • target polarization 0.7 (0.3) for NH3 (ND3) x x

  19. Determination of g1/F1 (approximately A1) • Dilution factor f varies from 0.1 to 0.3: used Lund model for n/p ratio (agrees with Hall C data) and preliminary Hall B data for A-dependence • Depolarization factor DLL(y) evaluated assuming • R=sL/sT same as for inclusive. • Assumed Aperp=0 (not measured) • “p+” and “p-” include some K+, K- for P>1.5 GeV • p0 events cleanly identified with two photons

  20. Dilution factor in SIDIS with NH3/ND3 Carbon/deuteron data averaged over our kinematics for SIDIS p+ CLAS@6GeV measurements (data available in bins in z,x) CLAS Preliminary • Assumed: • N/d same as C/d and p- and p0same as p+ • NO PT-depenence to d/p ratio Nuclear attenuation Measurements of PT-dependences of Nitrogen/proton ratios of pion multiplicities crucial for understanding of the dilution factor (ratio of counts from protons to counts from all materials in polarized target, mainly nitrogen).

  21. Polarized SIDIS: factorization tests Simple picture in valence region: sp(p+) ~ 4u(x)D+(z) + d(x)D-(z) sp(p-) ~ 4u(x)D-(z) + d(x)D+(z) Dsp(p+) ~ 4Du(x)D+(z) + Dd(x)D-(z) Dsp(p-) ~4Du(x)D-(z) + Dd(x)D+(z) (g1/F1)+-=[Dsp(p+)+Dsp(p-)]/[sp(p+)+sp(p-)] = [4Du(x) + Dd(x)] / [4u(x) + d(x)] = (g1/F1)inclusive Similarly for p0 (g1/F1)0=(g1/F1)inclusive Proton (g1/F1)+- and (g1/F1)0 should be independent of z and pt, and equal to inclusive (g1/F1)

  22. Polarized SIDIS factorization test GRVS g1/F1 for inclusive, for the sum of p+ ,p-, and for p0 are fairly consistent with each other in the range 0.4<z<0.7, as expected in LO if factorization works. Cuts used: Mx>1.4 GeV, Q2>1.1 GeV2, W>2 GeV

  23. pt-depenence of SIDIS proton A1 Signicant decrease of p+A1 with increasing pt! M.Anselmino et al hep-ph/0608048 m02=0.25GeV2 mD2=0.2GeV2 CLAS Preliminary p+ ALL can be explained in terms of broader kT distributions for f1 compared to g1

  24. VERY preliminary d/p ratios from CLAS- For z=0.55 and x=0.3, CLAS results consistent with Hall C, but when average over wider kinematic range 0.3<z<0.7 and 0.15<x<0.45, find: d/p increases with ptp for p+ d/p decreases with ptp for p- (for first bin, ratio 1.3, off plot!) d/p flat with ptp for p0 WHY? (acceptance, kinematic effect, nuclear effects, pr real physics, unfavored D- Wider in pt than favored D+ ?) p0 p+ p- PT(GeV) Essential to understand PT-dependence of deuteron/proton for precision measurements using polairzed NH3 target.

  25. D.S.Hwang (JLab-07) Helicity distributions: Diquark model Jakob, Mulders, Rodrigues, Nucl. Phys. A 1997 A.Bacchetta (JLab-07) q+ (quark aligned with proton spin) and q- (anti-aligned) may have very different kT-dependences

  26. Flavor Decomposition Use double spin asymmetries for different targets and final state particles to extract the helicity distributions for different flavors Sum over quark flavors Extraction of kT-dependent distributions q+ (f1+g1) and q- (f1-g1) will require unfolding of spin independent and spin dependent contributions

  27. SSA measurements at CLAS ep→e’pX W2>4 GeV2 CLAS PRELIMINARY p1sinf+p2sin2f Q2>1.1 GeV2 y<0.85 0.4<z<0.7 MX>1.4 GeV PT<1 GeV 0.12<x<0.48 p1= 0.059±0.010 p2=-0.041±0.010 p1=-0.042±0.015 p2=-0.052±0.016 p1=0.082±0.018 p2=0.012±0.019 • Significant SSA measured for pions with longitudinally polarized target • sin2f moments consistent with 0 for p0 (H1┴u=-H1 ┴d?)

  28. sUL ~ KM Longitudinally polarized target SSA using CLAS+IC 60 days of CLAS+IC (Inner calorimeter (L=1.5.1034cm-2s-1) curves, cQSM from Efremov et al Hunf=-5Hfav Hunf=-Hfav Hunf=0 • Provide measurement of SSA for all 3 pions, extract the Mulders TMD • Complimentary to BM and Collins effects study of the Collins fragmentation

  29. First glimpse of Twist-2 TMD h1L┴ For Collins fragmentation function use HERMES data Distribution functions from cQSM from Efremov et al PRELIMINARY CLAS-5.7GeV Systematic error only from unknown ratio of favored and unfavored Collins functions (R= H1d→p+/H1u→p+), band correspond to -2.5<R<0 • More data required with p- & p0 • Exclusive 2 pion background may be important: analysis in progress. The sign of h1L┴consistent with predictions Accessible in DY with Long.polarized protons

  30. Summary • Factorization in SIDIS pion production seems to work for 0.3<z<0.7, W>2 GeV, Mx>1.4 GeV, 0.2<x<0.5, Q2>1 GeV2. • Opens opportunity for studies of transverse momentum in PDF, fragmentation • Unpolarized moments cosf and cos2f extracted for p+ (BM?) • Puzzling results for negative pions in both spin-average d/p, and proton g1/F1 versus PT. Could both be due to different kT width of PDFs or favored and unfavored fragmentation differing? • The sin2f SSA measured, first glimpse of h1L┴ TMD. • Jlab upgrade will allow definitive measurements for x>0.1

  31. Future Plans • 20x more p+, p-, 40x more p0 for g1/F1 at 6 GeV on proton (using CLAS) • 3x more p+ and p- g1/F1 data on deuteron (Hall C) • Studies of q+/q- TMDs at Jlab 6 (2008-2009) • Transverse target measurements at 6 GeV • Measure TMDs with upgraded to 11 GeV electrons combined with wide acceptance of CLAS and high luminosity of Hall A/C will allow huge increase in kinematic coverage and statstical accuracy in SIDIS!

  32. 50o 13o Experimental Setup (CLAS EG1+IC) Polarized target (eg1) • solid NH3 polarized target • proton polarization >75% • high lumi ~ 1.51034 s-1cm-2 IC Inner Calorimeter (424 PbWO4 crystals) for the detection of high energy photons at forward lab angles (e1-DVCS).

  33. Support slides….

  34. Super-ratios versus transverse momentum Rpd+ Rpd- Both ratios independent of pt (to 0.3 GeV) for z=0.55

  35. x-depenence of SIDIS proton g1/F1 W>2 GeV, Q2>1.1 GeV2, 0.4<z<0.7 • Good agreement with • HERMES p+ data at • higher W. • x-dependence follows PEPSI (Lund) Monte Carlo using GRSV polarized PDFs (LO) • Magnitude also in good • agreement with simulation

  36. Missing mass of pions in ep->e’pX with 6 GeV electrons p0 D++ p- p+ n D0 Duality question: will factorization work if Mx<2 GeV, even though D(1232) resonance visible? For p-, guess need Mx>1.4 GeV.

  37. Another test: D-/D+ from Deuteron p+ to p- ratio sd(p+) = [u+d] [4D++D-] sd(p-) = [u+d] [4D-+D+] Results agree HERMES (higher W, Mx>2 GeV) up to z=0.7 (Mx>1.4 at pt=0), after rho correction

  38. Rpd+ Rpd- Both ratios agree PDF models 0.2<x<0.5 for z=0.55 (possible complications x>0.5)

  39. In region where factorization tests hold, can use data to constrain polarized PDFs in NLO analysis(separate out polarized up, down valence and sea quark parton distributions). CLAS 5.7 GeV PRELIMINARY

  40. In more detail, form super-ratios Simple LO picture in valence region: sp(p+) = 4u(x,pt)D+(z,pt) + d(x,pt)D-(z,pt) sp(p-) = 4u(x,pt)D-(z,pt) + d(x,pt)D+(z,pt) sd(p+) = [u(x,pt)+d(x,pt)] [4D+(z,pt) + D-(z,pt)] sd(p-) = [u(x,pt)+d(x,pt)] [4D-(z,pt) + D+(z,pt)] Rpd+= [sp(p+) + sp(p-)] / [sd(p+) + sd(p-)] = [4u(x,pt) + d(x,pt)] / 5[u(x,pt)+d(x,pt)] = sp(x)/sd(x) for any z, x, pt (if d and u have same pt depdendence)!

  41. Another test: d/p ratios for p+, p- p+ p- Again, ratios appear constant at these kinematics (x=0.3, Q2=2.5, z=0.55), although bit higher than Lund MC predictions

  42. Transverse target: p+ yield ratios to deuteron Multiple scattering and attenuation in nuclear environment introduces additional PT-dependence for hadrons

  43. Cross sections at x=0.3, z=0.55 versus Ptp Cross sections drop exponentially to Ptp-0.4: slopes for all four cases are similar and about 4.5 GeV-2 (vaires from about 4 to 5 GeV-2 depending on Q2 correction) p- from p p+ from p p- from d p+ from d

  44. SSA: x-dependence Twist-2 Higher Twist Data in rough agreement with Efremov et al. predictions, except for p0 sin(f) term (evidence for terms not involving Collins fragmentation?) 5.7 GeV PRELIMINARY

  45. pt-depenence of SIDIS proton g1/F1 dsp(p+) = 4du(x,pt)D+(z,pt) + dd(x,pt)D-(z,pt) dsp(p-) = 4du(x,pt)D-(z,pt) + dd(x,pt)D+(z,pt) Another explanation for opposite slopes for p+ and p- is that D-/D+ increases with pt (I.e. unfavored fragmentation has a wider transverse momentum dependence), as can be seen from above. This effect magnified in g1 compared to F1 due to dd negative while du positive

  46. z-depenence of SIDIS proton g1/F1 No significant z-dependence seen for p0 and p++ p- for 0.3<z<0.7, as expected if factorization holds Good agreement with PEPSI predictions including dropoff at high z for p-, due to increasing importance of dd(x), in turn due to increase of D+/D- with increasing z CLAS 5.7 GeV PRELIMINARY

  47. AULSSA: PT-dependence HT –SSA significant for p + and p 0 CLAS PRELIMINARY • sinf SSA p + increases with PT and is consistent with HERMES measurement.

  48. In region where factorization tests hold, analyze f depdendence of ALL, ALU, and AUL to learn about orbital motion of quarks, polarized fragmentation, and higher twist contributions. CLAS 5.7 GeV PRELIMINARY

  49. Significant phi-dependence seen for proton p+ sin(2f) in AUL of particular interest: leading twsit function Sensitive to L=0 and L=1 interference sin(f) and sin(2f) in AUL cos(f) in ALL sin(f) in ALU CLAS 5.7 GeV PRELIMINARY

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