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Spin Physics at

Spin Physics at. Delia Hasch. (for the HERMES collaboration). 17 th international spin physics symposium October 02-07, 2006; Kyoto (Japan). the spin of the nucleon. DS.

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Spin Physics at

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  1. Spin Physics at Delia Hasch (for the HERMES collaboration) 17th international spin physics symposium October 02-07, 2006; Kyoto (Japan)

  2. the spin of the nucleon DS Delia Hasch spin Physics at Hermes Kyoto (Japan), 02-10-2006 outline: • prerequisites • final results on g1 for the proton and deuteron • flavour decomposition of Dq talks by L.DeNardo, H.Jackson • new result on DG talk by P. Liebing • news on transversity & friends talks by M.Diefenthaler, M.Contalbrigo • hunting DL: DVCS, excl. r0 talks by W.D.Nowak, H.Guler, E. Kinney • new results on L polarisation (not covered)talk by K.Rith

  3. Hermes @ DESY kinematic range = 7 GeV: 0.2 < Q2 < 20 GeV2 0.004 < x <0.9 for Q2 > 1 GeV2 : x > 0.02 self-polarised electrons: e <Pb>~ 53±2.5 % • resolution: dp/p~2%, dq<1 mrad • particle ID: lepton ID with e~98%, hadron contamination <1% • RICH: p, K, p ID within 2<Eh<15 GeV 1H→<|Pt|> ~ 85 ±3.8 % 2H→<|Pt|> ~ 84 ±3.5 % 1H <|Pt|> ~ 74 ±4.2 % pure nuclear-polarised atomic gas, flipped at 90s time intervals 27.5 GeV (e+/e-) <Pb>~ 53±2.5 % Delia Hasch spin Physics at Hermes Kyoto (Japan), 02-10-2006 Stern-Gerlach separation

  4. polarised structure function g1 Delia Hasch spin Physics at Hermes Kyoto (Japan), 02-10-2006

  5. polarised structure function g1 [Q2>1 GeV2 data only] see talk by L. DeNardo x MS a0= DS(theory) (exp) (evol) = 0.330 ± 0.011 ± 0.025 ± 0.028 Delia Hasch spin Physics at Hermes Kyoto (Japan), 02-10-2006 assume saturation of G1d :

  6. Duv and Ddv (quite) well determined: • Duv >0,Ddv <0 • Dq and DG weakly constraint by data Delia Hasch spin Physics at Hermes Kyoto (Japan), 02-10-2006 Dq and DG from inclusive data

  7. unpolarised DIS • need more direct probes Delia Hasch spin Physics at Hermes Kyoto (Japan), 02-10-2006 how to further proceed ? • Dq and DG from inclusive DIS data via evolution equations : • requires wide kinematic range in Q2 and x • only fixed targetspin experiments so far … need polarisedcollider to extend kinematic coverage OR:

  8. probability that struck quark of flavour f fragments into hadron of type h with energy fraction z fragmentation function distribution function , z=Eh/n Delia Hasch spin Physics at Hermes Kyoto (Japan), 02-10-2006 polarised semi-inclusive DIS

  9. probability that struck quark of flavour f fragments into hadron of type h with energy fraction z flavour tagging p+ ud K- us p- ud , z=Eh/n Delia Hasch spin Physics at Hermes Kyoto (Japan), 02-10-2006 polarised semi-inclusive DIS ‘purities’ (based on MC tuned to HERMES multiplicities)

  10. sea quarks (u, d, s ,s) compatible with 0 :in measured x-range: (0.02-0.6): - - - Delia Hasch spin Physics at Hermes Kyoto (Japan), 02-10-2006 quark/anti-quark helicity distributions [HERMES, PRL92(2004), PRD71(2005)] u quarks large positive polarisation d quarks negative polarisation x

  11. strange quarks carry no isospin (same in p, n) • deuterium is isoscalar target •  fragmentation simplifies all needed information extracted from HERMES data alone: • A1d(x,Q2) , A1K(x,Q2) • kaon multiplicities assumptions:  isospin symmetry  charge conjugation Delia Hasch spin Physics at Hermes Kyoto (Japan), 02-10-2006 ‘isoscalar’ extraction DS [HERMES, PRL92(2004), PRD71(2005)]

  12. strange quarks carry no isospin (same in p, n) • deuterium is isoscalar target •  fragmentation simplifies all needed information extracted from HERMES data alone: • A1d(x,Q2) , A1K(x,Q2) • kaon multiplicities assumptions:  isospin symmetry  charge conjugation Delia Hasch spin Physics at Hermes Kyoto (Japan), 02-10-2006 ‘isoscalar’ extraction DS [HERMES, PRL92(2004), PRD71(2005)] x x

  13. see talk by H. Jackson Delia Hasch spin Physics at Hermes Kyoto (Japan), 02-10-2006 ‘isoscalar’ extraction DS [HERMES, PRL92(2004), PRD71(2005)]  earlier Ds result confirmedwith factor 2 smaller errors: xDS(x)/2 x

  14. Delia Hasch spin Physics at Hermes Kyoto (Japan), 02-10-2006 direct measurement of DG • golden channel: charm production • @HERMES: hadron production at high PT hard scale is PT method I: method II: MC: PYTHIA6.2 Bg-processes: DIS, QCDC, direct+resolvedg

  15. Dg/g see talk by P. Liebing +0.127 x (sys-model) -0.105 Delia Hasch spin Physics at Hermes Kyoto (Japan), 02-10-2006 direct measurement of DG • golden channel: charm production • @HERMES: hadron production at high PT : hard scale is PT method I: method II: MC: PYTHIA6.2 Bg-processes: DIS, QCDC, direct+resolvedg <m2>=1.35 GeV2

  16. Delia Hasch spin Physics at Hermes Kyoto (Japan), 02-10-2006 quark structure of the nucleon

  17. Delia Hasch spin Physics at Hermes Kyoto (Japan), 02-10-2006 quark structure of the nucleon unpolarised quarks and nucleons transversely polarised quarks and nucleons h1(x): helicity flip chiral-odd  needs a chiral odd partner: SIDIS: COLLINS-FF  azimuthal asymmetry AUT longitudinally polarised quarks and nucleons

  18. Delia Hasch spin Physics at Hermes Kyoto (Japan), 02-10-2006 HERMES transverse running 2002-05 transversally polarised p (Pt = 0.78±0.04) 0.3T transverse holding field 2002: first results [PRL94(2005)] preliminary data 2002-2004  [hep-ex/0507013]

  19. Delia Hasch spin Physics at Hermes Kyoto (Japan), 02-10-2006 asymmetries and moments [angle and moments definitions according to Trento conventions] Collins moment Sivers moment Collins and Sivers moments extracted by fitting the asymmetry with:

  20. see talk by M. Diefenthaler Delia Hasch spin Physics at Hermes Kyoto (Japan), 02-10-2006 Collins asymmetries p+/- • significantly positivep+ and • negativep-asymmetries • unexpected largep- • role of unfavoured • fragmentation function? • measurement of from K+/-

  21. Delia Hasch spin Physics at Hermes Kyoto (Japan), 02-10-2006 what can we learn from Collins AUT? [Efremov et al. hep-ph/0603054] • h1 from cQSM • Collins FF: x-dependence: Hermes data fitted to obtain parameters for ansatz for CollinsFF z-dependence: BELLE data fitted and asymmetry for Hermes calculated • HERMES+BELLE data in agreement 

  22. see talk by M. Diefenthaler Delia Hasch spin Physics at Hermes Kyoto (Japan), 02-10-2006 Sivers asymmetries p+/- • significantly positive p+ • asymmetry • requires non-zero orbital angular momentum • first hint of naïve T-odd DF from DIS  test of universality: K+/- • D1 known  Sivers DF • can be extracted from • HERMES data !

  23. [Jaffe etal,PRL80,1998] [Radici etal,PRD65,2002] Delia Hasch spin Physics at Hermes Kyoto (Japan), 02-10-2006 two-hadron asymmetry 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  needs new unknown 2hadron fragmentation function Mpp Mpp

  24. see talk by M. Contalbrigo Delia Hasch spin Physics at Hermes Kyoto (Japan), 02-10-2006 two-hadron asymmetry • positive moments for all invariant mass bins 0.040±0.009 (stat) ±0.003 (sys)

  25. Q2 Vector mesons (r, w, f): H E Pseudoscalar mesons (p, h): H E DVCS (g) depends on H, E, H, E Quantum number of final state selects different GPDs: ~ ~ ~ ~ t ( H + E) x dx =Jq = 1/2 DS+ Lz 10-30%(DIS) Delia Hasch spin Physics at Hermes Kyoto (Japan), 02-10-2006 hunting for Lq  hard exclusive processes: Generalised Parton Distributions Q2>>, t<<  

  26. MC Bethe-Heitler associated BH + data Delia Hasch spin Physics at Hermes Kyoto (Japan), 02-10-2006 exclusivity @HERMES e+/e- 27.5 GeV Pb=55% (detected) • missing mass (energy) technique background estimated by MC no recoil detection

  27. DVCS-BH interference leads to non-zero azimuthal asymmetry Delia Hasch spin Physics at Hermes Kyoto (Japan), 02-10-2006 Deeply Virtual Compton Scattering Bethe-Heitler DVCS Bethe-Heitler

  28. ~ DsC~cosf∙Re{ H+ xH +… } ~ see talk by H. Guler DsLU~sinf∙Im{H+ xH+ kE} DsUT polarisation observables: ~ DsUL~sinf∙Im{H+ xH+ …} beam target Delia Hasch spin Physics at Hermes Kyoto (Japan), 02-10-2006 DVCS asymmetries I~Ds  different charges: e+ e-(only @HERA!):  H H ~  H DsUT~sinf∙Im{k(H- E) + … } H, E  kinematically suppressed x = xB/(2-xB ),k = t/4M2

  29. e+/- p→ e+/- p g (MX<1.7 GeV) (in HERMES acceptance) Regge, D-term Regge, no D-term fac., D-term fac., no D-term Delia Hasch spin Physics at Hermes Kyoto (Japan), 02-10-2006 DVCS: beam charge asymmetry [hep-ex/0605108, subm.to PRL] GPD calculations: different parametrisations forH • Vanderhaeghen(1999/02)–  AC sensitive to GPD-models tiny e-p sample (L=10pb-1) HERA: 2005/06 e- beam (10x)

  30. Delia Hasch spin Physics at Hermes Kyoto (Japan), 02-10-2006 DVCS: longitudinal target-spin asymmetry sinf in agreement with GPD models unexpected large sin2f (twist-3)

  31. see talk by W.D. Nowak Delia Hasch spin Physics at Hermes Kyoto (Japan), 02-10-2006 DVCS: transverse target-spin asymmetry [2002-2004 data] GPD model by: [Goeke et al. (2001)] [Ellinghaus et al. (2005)] first model dependent constrain on Ju+Jd

  32. see talk by E. Kinney Delia Hasch spin Physics at Hermes Kyoto (Japan), 02-10-2006 r0transverse target-spin asymmetry interference of H and E: sS ~ |ST| sin (f-fS) E∙H [curves: Vinnikov et al. (2005)] GPD model calculations:quark+gluon GPDs Erelated toJq TSA sensitive to Jq • add 2005 data:sL/sT separation (meson production: factorisation for longitudinal photons only)

  33. Delia Hasch spin Physics at Hermes Kyoto (Japan), 02-10-2006 summary: HERMES view at the nucleon structure polarised DIS + HERMES: from unpolarised DIS first glimpse a0 =0.330±0.025(exp)  signals of GPDs  Ju+Jd transversity is non-zero! first T-odd DF in DIS direct flavour decomp. new constrain on Ds

  34. Backup slides

  35. Delia Hasch spin Physics at Hermes Kyoto (Japan), 02-10-2006 HERMES futureJune 2007 • add 2005: p data transversity+friends exclusive AUT(DVCS, r0, p0)  2006-07: e+/e- 27.5 GeV dedicated measurements of hard exclusive processes with recoil

  36. contribution from exclusive VM in sidis sample  basically no VM contribution for kaons

  37. polarised gluon distribution 3 data samples: • ‘anti-tagged’ : e+ not in acceptance • pT measured w.r.t. beamline • ‘tagged’ : e+ identified • hadron pairs  different bg contributions, different systematics Dg/g

  38. DVCS: TTSAconstrain on Ju+Jd

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