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SINGLE HADRON TRANSVERSE SPIN ASYMMETRIES FROM COMPASS

SINGLE HADRON TRANSVERSE SPIN ASYMMETRIES FROM COMPASS. Franco Bradamante University of Trieste and INFN Trieste. on behalf of the COMPASS Collaboration. Kyoto, October 3, 2006. THE SPECTROMETER. two stages spectrometer Large Angle Spectrometer (SM1) Small Angle Spectrometer (SM2)

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SINGLE HADRON TRANSVERSE SPIN ASYMMETRIES FROM COMPASS

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  1. SINGLE HADRON TRANSVERSE SPIN ASYMMETRIES FROM COMPASS Franco BradamanteUniversity of Trieste and INFN Trieste on behalf of the COMPASS Collaboration Kyoto, October 3, 2006

  2. THE SPECTROMETER two stages spectrometer • Large Angle Spectrometer (SM1) • Small Angle Spectrometer (SM2) tracking, calorimetry, PID SciFi Silicon Micromegas GEMs Straws SDC MWPC W45 MuonWall SM2 E/HCAL E/HCAL SM1 MuonWall Polarised Target RICH mbeam • high energy beam • broad kinematical range • large angular acceptance

  3. dN/dz 4000 3He – 4He Dilution refrigerator (T~50mK) 2000 superconductive Solenoid (2.5 T) Dipole (0.5 T) 0 -1000 0 1000 zvtx (mm) two 60 cm long cells with opposite polarization (systematics) 3 m 6 m 5 m photon detectors C4F10 THE TARGET SYSTEM THE RICH DETECTOR solid target operated in frozen spin mode threshold momenta • pp = 2 GeV/c • pK = 9 GeV/c • pP =17 GeV/c fully efficient for transverse data in 2003 and 2004

  4. DIS events (106) DATA TAKING 2002-2004 transversely polarised deuteron target~ 20% of the running time Collins and Sivers asymmetries published results 2002 prel results 2002-2004 with RICH PID Two hadron asymmetries prel results 2002-2004 Λ polarimetry prel results 2002-2003

  5. SINGLE HADRON ASYMMETRIES unpol B and T transvely polarised target SIDIS cross-section long pol B and/or T hazimuthal angle of the hadron s’ azimuthal angle of the transverse spin of the struck quark sazimuthal angle of the transverse spin of the initial quark s’ = p - s FS at leading order Sivers Collins beam polarization independent angles  independent extraction of the asymmetries

  6. EVENT SELECTION DIS events Q2 > 1 GeV2 W2> 25 GeV2 0.1 < y < 0.9 hadrons pht > 0.1 GeV/c z > 0.2 (all h) z > 0.25 (leading h) Q2 = 2.4 (GeV/c)2 W = 9.4 GeV/c2 xBj  0.035 2002 data

  7. ASYMMETRIES 2003-2004 vs 2002 results from 2003-2004 data released in April (DIS2006) comparison with the published 2002 data increase in statistics by a factor of 7! PRL 94 (2005) 202002

  8. DIS2006 DIS2006 COLLINS ASYMMETRIES 2002-2004 • small errors (~1%) • small asymmetries • cancellation between p and n (lh and ah)

  9. preliminary COMPASS 2002-2004 preliminary COMPASS 2002-2004 Vogelsang and Yuan Efremov et al preliminary COMPASS 2002-2004 preliminary COMPASS 2002-2004 Anselmino et al, SB Anselmino et al, Tq = q COLLINS ASYMMETRY results from model calculations: • good fits to the proton HERMES DATA withCollins FF: favoured ~ – unfavored, at variance with unpolarised case • comparison with BELLE DATA ok:universality of the Collins effect, hints on Tu • comparison with the deuteron COMPASS 2002 DATA okTd ~ unconstrained comparison with the new COMPASS 2002-2004 data • agreement not so good as with COMPASS 2002 data • from a global fit of all the present data probably stronger constrains on the transversity PDFs and in particular on Td (x)

  10. DIS2006 DIS2006 SIVERS ASYMMETRIES 2002-2004 • small errors (~1%) • small asymmetries • cancellation between p and n (lh and ah)

  11. What have we learnt over the past 2 years ?Sivers Asymmetry comparison of the same calculations with the COMPASS 2002-04 data preliminary COMPASS 2002-2004 preliminary COMPASS 2002-2004 Collins et al Vogelsang and Yuan preliminary COMPASS 2002-2004 • as in the Collins case, agreement not always so good as for 2002 data • from a global fit of the present HERMES and COMPASS data probably stronger constrains on the Sivers DFs Anselmino et al

  12. hadrons 100% no RICH information 5% pions 77% after all cuts kaons 12% protons 3% p±, K± ASYMMETRIES 2003-2004 • same DIS event selection and hadron definition as before • plus • PID based on RICH response final sample additional systematic tests: RICH stability  systematic errors smaller than statistical ones

  13. p±, K± SIVERS ASYMMETRIES 2003-2004 GPD2006

  14. p±, K± Collins Asymmetries 2003-2004 GPD2006 again, difficult to see an effect …

  15. SUMMARY New precise DIS deuteron data from COMPASS are now available In all the channels investigated in so far the measured deuteron asymmetries are very small, compatible with zero Collins and Sivers asymmetries for positive and negative hadrons, p±, K± PRESENT PICTURE Collins: u quark dominanceDT0D(fav.) ~ - DT0D(unfav) for u quark DTd from global analysis (NEW COMPASS DATA) Sivers: D0Tu ~ - D0Td

  16. One of the most recent citations COMPASS 2002 data Evidence for the Absence of Gluon Orbital Angular Momentum in the Nucleon S.J. Brodsky, S. Gardner SLAC-PUB-12062, Aug 2006. Subm. Phys.Lett.B, hep-ph/0608219 Due to the smallness of the anomalous magnetic moment of the deuteron the orbital motion of the quarks should not contribute to the Sivers SSA of the deuteron. Thus

  17. riserva

  18. Anselmino et al, BNL UM 2006 Soffer bound & Tq = q Vogelsang Yuan, PRD 72, 054028 (2005) Soffer bound Efremov et al, PRD 73, 094025 (2006) chiral quark-soliton model COLLINS ASYMMETRY important theoretical work on the interpretation of the data assumptions on Tq and fit of HERMES 2002-2004 data to exctract the Collins FF

  19. Vogelsang Yuan, PRD 72, 054028 (2005) result: d SDF ~ -2 u SDF Collins et al, PRD 73, 014021 (2006) input: d SDF = - u SDF Anselmino et al, PRD 72, 094007 (2005) u SDF ~ - d SDF fit using the COMPASS 2002 data too SIVERS ASYMMETRY important theoretical work on the interpretation of the data use of the HERMES 2002-2004 data to exctract/check the Sivers DF

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