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Measurement of Transversity+friend in SIDIS

This seminar discusses the measurement of transversity and related quantities in Semi-Inclusive Deep Inelastic Scattering experiments. It covers the details of the extraction process and discusses acceptance effects, virtual photon contributions, and fragmentation functions.

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Measurement of Transversity+friend in SIDIS

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  1. Measurement of Transversity+friendin SIDIS Delia Hasch RHIC – Spin physics seminar BNL, NY (US), 22 Feb 2006

  2. outline Introduction  Transversity+friends : Theory see Mauro’s talk yesterday! case: SIDIS Experiments: Details of extraction:  acceptance effects  VM contributions  DF extraction C L A S ,Hall A

  3. probability that struck quark of flavour f fragments into hadron of type h with energy fraction z fragmentation function distribution function polarised semi-inclusive DIS Q2 …hard scale , z=Eh/n

  4. sidis cross section f1 g1 sLT beam target polarisation

  5. mixing of azimuthal moments experiment: target polarisation w.r.t. beam direction (l) theory: polarisation w.r.t. virtual photon direction (q) [Diehl, Sapeter EPJC41(2005)] at HERMES energies: cosqg*  1, sinqg* up to 15%

  6. mixing of azimuthal moments experiment: target polarisation w.r.t. beam direction (l) theory: polarisation w.r.t. virtual photon direction (q) [Diehl, Sapeter EPJC41(2005)] at HERMES energies: cosqg*  1, sinqg* up to 15%

  7. HERMES: 27.5 GeV e+/- Compass: 100-190 GeV m+ Jlab: HallA,B up to 6 GeV e- prerequisites • good hadron • identification  full phi coverage!! HERMES: d, p Compass: d , p Hall A,B: p, n

  8. e.g. HERMES 0.3T transverse holding field forward spectrometer: “box” acceptance (same for COMPASS) split in two halfs

  9. acceptance coverage in f andfs • good acceptance in f • and fs, though not perfect • fit amplitudes <sin(f+fs)> • and <sin(f-fs)> simultaneously prevents mixing of Collins + Sivers via acceptance!

  10. extraction method: MC tests • generate Collins + Sivers asymmetries (gaussian ansatz in ) • analyse MC like data… extraction method robust to effects of: •  acceptance+detector • smearing • QED radiative effects • target holding field • Collins-Sivers cross • contaminations

  11. asymmetries and moments I […]  convolution integral over initial (pT) and final (kT) quark transverse momenta

  12. solving the convolution integral weighted asymmetries:  acceptance effects not yet under control  gaussian ansatz (model dependent)

  13. interpretative uncertainty from exclusive VM wanted: SIDIS process exclusive r0 production: different physics… one of thepescapes…

  14. interpretative uncertainty from exclusive VM wanted: SIDIS process exclusive r0 production: different physics…

  15. interpretative uncertainty from exclusive VM • transfer coefficients • from MC • decay angular distributions • spin density matrix for transverse • target NEEDED a CHECK: • difference (p+-p-) asymmetries significantly non-zero! however: NO agreement if processes should be excluded…

  16. Sivers asymmetries 2002-2004 • significantly positive p+ asymmetry • requires non-zero orbital • angular momentum • first hint of naïve T-odd DF • from DIS •  test of universality: • D1 known  Sivers DF can be extracted

  17. extracting quark distributions purity formalism: … from a fragm. model in MC tuned to hadron multiplicities e.g.: extraction of quark helicity distributions: first direct 5-flavour separation

  18. U.Elschenbroich, thesis (gaussian ansatz, symmetric sea) extracting quark distributions purity formalism: Sivers:

  19. Collins asymmetries 2002-2004 • positive p+ and negative p- asymmetries … as maybe expected: (Du>0  du >0 Dd<0  dd <0 ) • unexpected largep- role of unfavoured fragmentation function? • NEEDED! • BELLE 

  20. map out solution space: Hdisfav ≈ - Hfav Hdisfav / Hfav why are p-Collins asymm. so large? DIS on p target always dominated by u-quark scattering  … expected: positive  … expected: ~zero minimal assumptions:  AUT is leading twist  CollinsFF obeys fav/disfav symmetry

  21. revisiting the longitudinal target SSA

  22. revisiting the longitudinal target SSA [PRL 84 (2000) 4047 : 160 citations !] • interpreted in terms of arising • from transv. Component • (tw-3 contributions essentially neglected)  subtract AUT part from AUL to obtain pure AUL moments:

  23. revisiting the longitudinal target SSA • AUL is almost-entirely • longitudinal (i.e. tw-3) • recent, more complete • theoret. analysis: …theoretical revisit needed!

  24. 2hadron asymmetries

  25. interference fragmentation function interference arises from different partial waves of p+p- system !collinear factorisation!  relativ. momentum: R=(Pp++Pp-)/2 can have transv. component even when integrating over PT of the pair [Radici etal,PRD65,2002] [Jaffe etal,PRL80,1998]

  26. interference fragmentation function • for >2 hadrons: all combinations • excl. r0 excluded

  27. interference fragmentation function • positive moments for • all invariant mass bins 0.040±0.009 (stat) ±0.003 (sys)

  28. transversity+friends from 02-05 data:  2D binning for single pion asymmetries  charged kaon asymmetries  working on weighted asymmetries  cosf and cos2f moments  Sivers extraction (purity formalism) … waiting Belle data for CollinsFF HERMES future2007 • till Nov2005: p • transversity+friends • exclusive AUT(DVCS, r0, p+)

  29. HERMES future2007 • till Nov2005: p • transversity+friends • exclusive AUT(DVCS, r0, p+)  2006-07: e+/e- 27.5 GeV dedicated measurements of hard exclusive processes with recoil

  30. transversity+friends @COMPASS @JLAB

  31.  proton target in 2006: 30 days NH3 TMDs @COMPASS Collins Sivers  all asymmetries compatible with zero  2007/08 priority of hadron program

  32. 424 PbWO4 ……..crystals IC CLAS+IC CLAS TMDs @JLab (6 GeV) • longitudinal target/beam asymmetries from • CLAS: AUL ALU PRELIMINARY p+

  33. 424 PbWO4 ……..crystals IC TMDs @JLab (6 GeV) • longitudinal target/beam asymmetries from • CLAS: AUL PRELIMINARY Mulders

  34.  valence region • small z-range •  limited f acceptance TMDs @JLab (6 GeV )  transverse target polarisation: projections for 24 days approved proposal @Hall-A with 3He  neutron p-

  35. fragmentation function  e+e- fragmentation in sidis

  36. e+ e- FFfrom e+e- • add p0: • favoured/unfavoured • extension to IFF • straight forward Milestone!

  37. first extraction of TMDs feasible e+ e- current facilities: near+mid term future • Collins/2hadron FF • with high accuracy JLAB @6GeV √ Sivers function from HERMES very near future: √ transversity from HERMES+BELLE √ Mulders function from CLAS+BELLE

  38. Backup slides Statistics: 02-04 : ~70 pb-1 05 ~150 pb-1

  39. pp  AN for inclusive hadrons, di-jets  Sivers AT in jets:  Collins FF  IFF ATT inclusive jets, DY STAR, PHENIX, Brahms PAX SIDIS  AUT, ALT, AUL, ALU, AUU for single and double hadrons L production, VM HERMES, Compass, JLab@6GeV JLab@12GeV, EIC TMDs e+e-  CollinsFF , IFF BELLE factorisation universality future TMD pp sidis e+e- measurements RHIC PAX HERMES COMPASS JLab EIC BELLE summary Summary

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