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HIGHLIGHTS FROM THE COMPASS EXPERIMENT @ CERN

HIGHLIGHTS FROM THE COMPASS EXPERIMENT @ CERN. F. Bradamante University of Trieste and INFN Trieste on behalf of the Collaboration Sixth International Conference on Perspectives in Hadronic Physics Trieste, May 16, 2008.

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HIGHLIGHTS FROM THE COMPASS EXPERIMENT @ CERN

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  1. HIGHLIGHTS FROM THE COMPASSEXPERIMENT @ CERN F. Bradamante University of Trieste and INFN Trieste on behalf of the Collaboration Sixth International Conference on Perspectives in Hadronic Physics Trieste, May 16, 2008

  2. COmmon Muon and Proton Apparatusfor Structureand Spectroscopy NA58 Czech Republic, Finland, France, Germany, India, Israel, Italy, Japan, Poland, Portugal, Russia Bielefeld, Bochum, Bonn, Burdwan, Calcutta, CERN, Dubna, Erlangen, Freiburg, Heidelberg, Helsinki, Lisbon, Mainz, Miyazaky, Moscow, Munich, Nagoya, Prague, Protvino, Saclay, Tel Aviv, Torino, Trieste, Warsaw 28 Institutes, ~230 physicists F. Bradamante, 6th International Confrence on Perspectives in Hadronic Physics

  3. COMPASS • since 2002 taking data with a new spectrometer with outstanding performances • merging of two programmes: F. Bradamante, 6th International Confrence on Perspectives in Hadronic Physics

  4. Experiments with muon beam ΔG/G g1 Transverse spin effects Flavor decomposition of spin distribution functions Vector meson production Spin transfer inΛ-hyperon production Experiments with hadron beams Pion and Kaon polarizabilities Diffractive production of exotic states Search for glueballs Light meson spectroscopy Production of double charmed baryons Physics program of COMPASS F. Bradamante, 6th International Confrence on Perspectives in Hadronic Physics

  5. luminosity: ~5 . 1032 cm-2 s-1 beam intensity: 2.108m+/spill (4.8s/16.2s) beam momentum: 160 GeV/c longitudinally polarised muon beam longitudinally or transversely polarised target calorimetry particle identification LHC SPS N F. Bradamante, 6th International Confrence on Perspectives in Hadronic Physics

  6. 160 GeVμ SM2 SM1 6LiD Target The Spectrometer for the Muon Programme Trigger-hodoscopes μFilter ECal & HCal 50 m RICH MWPC Straws TWO STAGE SPECTROMETER: Gems Drift chambers Polarized beam and target Micromegas SAT, LAT, PID Silicon SciFi 0.003 < x < 0.5 10-3 < Q2 < 10 GeV2 F. Bradamante, 6th International Confrence on Perspectives in Hadronic Physics

  7. WHERE ARE WE ? • in 2002, 2003, 2004, 2006 and 2007 COMPASS has taken data in themuon programconfiguration 160 GeV, polarized m beam2002-2006 6LiD polarized target (~polarized deuterons) 2007 NH3 polarized target (~polarized protons) 2000 TB ~ 5·1010 events • pilot run in 2004 for hadron program • 2008: hadron beam at 190 GeV for diffractive and central production physics results • DG/G 1.pion polarizability • DS 2.PWA in diffractive • Transversity scattering • Cahn asymmetry • Pentaquark • Exclusive ρ0 • Λ physics F. Bradamante, 6th International Confrence on Perspectives in Hadronic Physics

  8. THE COMPASS MUON PROGRAM TWO CLASSES OF PHENOMENA: • LONGITUDINAL SPIN CASE • TRANSVERSE SPIN CASE F. Bradamante, 6th International Confrence on Perspectives in Hadronic Physics

  9. LONGITUDINAL SPIN CASE: the beginning  SPIN CRISIS F. Bradamante, 6th International Confrence on Perspectives in Hadronic Physics

  10. LONGITUDINAL SPIN CASE from polarised lepton – polarised nucleon DIS with and first moments: from measurement of EMC in 1988 and using complementary information from neutron and hyperon β–decay one obtained at variance with naïve expectation since necessity for measuring SMC, SLAC, HERMES and in SIDIS SMC, HERMES, COMPASS in SIDIS HERMES, COMPASS F. Bradamante, 6th International Confrence on Perspectives in Hadronic Physics

  11. LONGITUDINAL SPIN CASE physics results ΔG/G F. Bradamante, 6th International Confrence on Perspectives in Hadronic Physics

  12. MEASUREMENTS OF THEGLUON POLARIZATION FOUR LINES OF ATTACK: • Double spin asymmetry of the OPEN CHARM cross-section in high energy µD scattering • Double spin asymmetry of the HIGH-pt HADRON PAIRS in high energy µD DIS (Q2 > 1 GeV2) • Double spin asymmetry of the high-pt hadron pairs in high energy µD scattering (Q2 < 1 GeV2) • Measurement of g1 of the deuteron and QCD fit of all the world data F. Bradamante, 6th International Confrence on Perspectives in Hadronic Physics

  13. N DG/G at COMPASS Photon Gluon Fusion q = c cross section differencein charmed meson production → theory well understood → experiment challenging q = u,d,s cross section difference in 2+1 jet productionin COMPASS: events with 2 hadrons with high-pt → experiment easy → theory more difficult F. Bradamante, 6th International Confrence on Perspectives in Hadronic Physics

  14. ΔG/G from Open Charm F. Bradamante, 6th International Confrence on Perspectives in Hadronic Physics

  15. D mass spectra D0 → K π nD* = 8675 nD0 = 37398 D0 → K ππ0 APS, 13 April 2008 G.K. Mallot 15 F. Bradamante, 6th International Confrence on Perspectives in Hadronic Physics

  16. DG/G from open charm 2002 – 2006 data D0 + D* • ΔG/G = -0.49 ± 0.27 (stat) ± 0.11 (syst) • @ <xg> ~ 0.11, <m2> ~ 13 (GeV/c)2 preliminary 16 F. Bradamante, 6th International Confrence on Perspectives in Hadronic Physics

  17. ΔG/G from High-pt hadron pairs F. Bradamante, 6th International Confrence on Perspectives in Hadronic Physics

  18. QCD- Compton PGF LO DIS ΔG/G from High-pt hadrons, Q2 > 1 (GeV/c)2 PGF and background F. Bradamante, 6th International Confrence on Perspectives in Hadronic Physics

  19. ΔG/G from High-pt hadrons, Q2 > 1 (GeV/c)2 2002 – 2004 data: High pT, Q2 > 1 GeV/c2 • ΔG/G = 0.08 ± 0.10 (stat) ± 0.05(syst) • @ <xg> = 0.082 (range: 0.055 – 0.123), m2 ~ 3 (GeV/c)2 preliminary F. Bradamante, 6th International Confrence on Perspectives in Hadronic Physics

  20. QCD- Compton PGF LO DIS ΔG/G from High-pt hadrons all Q2 low Q2 resolved photon F. Bradamante, 6th International Confrence on Perspectives in Hadronic Physics

  21. ΔG/G from High-pt hadrons, Q2 < 1 (GeV/c)2 2002 – 2004 data: High pT, Q2 < 1 GeV/c2 ΔG/G = 0.016 ± 0.058 (stat) ± 0.055 (syst) • @ <xg> = 0.085, m2= 3 GeV2 preliminary F. Bradamante, 6th International Confrence on Perspectives in Hadronic Physics

  22. Gluon Polarization COMPASS preliminary results high-pT pairs, Q2>1GeV2 : 2002–2004 ΔG/G = 0.08 ± 0.10 (stat) ± 0.05(syst) • @ <xg> = 0.082 (range: 0.055 – 0.123), m2 ~ 3 (GeV/c)2 high-pt pairs, Q2< 1GeV2 : 2002–2004 ΔG/G = 0.016 ± 0.058 (stat) ± 0.055 (syst) • @ <xg> = 0.085, m2= 3 GeV2 open charm: 2002–2006 ΔG/G = -0.49 ± 0.27 (stat) ± 0.11 (syst) • @ <xg> ~ 0.11, <m2> ~ 13 (GeV/c)2 F. Bradamante, 6th International Confrence on Perspectives in Hadronic Physics

  23. Summary of results new high-pT point new charm point G.K. Mallot F. Bradamante, 6th International Confrence on Perspectives in Hadronic Physics

  24. g1d F. Bradamante, 6th International Confrence on Perspectives in Hadronic Physics

  25. g1 of the deuteron (2002-2003) Phys Lett B 612 (2005) 154 • most precise measurement for 0.004 < x < 0.03 • new NLO QCD fit, precision of a0 improves factor 2 (Q2 = 4 GeV2) F. Bradamante, 6th International Confrence on Perspectives in Hadronic Physics

  26. CONCLUSION from ΔG MEASUREMENTS: ΔG SMALL more precise measurements will come soon COMPASS 2006 RHIC RUN6 …. interest in orbital angular momentum GPD’s Ji’s SUM RULE F. Bradamante, 6th International Confrence on Perspectives in Hadronic Physics

  27. more on LONGITUDINAL SPIN CASE MEASUREMENT OF VALENCE QUARK POLARISATION F. Bradamante, 6th International Confrence on Perspectives in Hadronic Physics

  28. valence quark polarisation hadron asymmetries F. Bradamante, 6th International Confrence on Perspectives in Hadronic Physics

  29. valence quark polarisation comparison with other experiments F. Bradamante, 6th International Confrence on Perspectives in Hadronic Physics

  30. The Transverse Spin Case F. Bradamante, 6th International Confrence on Perspectives in Hadronic Physics

  31. Transverse Spin case Large effects observed in hadronic interactions F. Bradamante, 6th International Confrence on Perspectives in Hadronic Physics

  32. q(x) Dq(x)DTq(x) Transverse Spin case at leading order a third PDF is necessary for a complete description of the structure of the nucleon Theoretical developments: Large effects observed in hadronic interactions • DTq(x) being chiral-odd, it can be measured only in conjunction • with another chiral-odd partner: Collins function SIDIS DY measurable in e+e- hadrons • relevance of transverse momentum dependent (TMD) PDF and FF Sivers function Many Workshops in recent years on Transverse Momentum, spin, and position distributions of partons in hadrons F. Bradamante, 6th International Confrence on Perspectives in Hadronic Physics

  33. Transversity – single hadron - 1 Collins and Sivers angles • C = h- S’ S = h- S S ’ azimuthal angle of spin vector of fragmenting quark (S’’ = p- S) hazimuthal angle of hadron momentum F. Bradamante, 6th International Confrence on Perspectives in Hadronic Physics

  34. Transversity – single hadron- 2 first measurements of transverse spin asymmetries in DIS of high energy muons on a transversely polarizeddeuteron target published single hadron asymmetries from 2002-2004 runs • Collins: related to transverse quark distributions • Sivers: related to intrinsic kT Phys Rev Lett 94 (2005) 202002 Nucl Phys B765 (2007) 31 F. Bradamante, 6th International Confrence on Perspectives in Hadronic Physics

  35. Collins asymmetry for pions and kaons preliminary 2002-2004 data proton (virtual photon asymm) (lepton beam 2002-05  DIS07) final CERN-PH-EP/2008-002hep-ex/0802.2160 (PRL) 2003-2004 data deuteron (virtual photon asymm) COMPASS sign convention F. Bradamante, 6th International Confrence on Perspectives in Hadronic Physics

  36. Independent Measurement of the Collins FF measurable in e+e– annihilation • first attempts to measured it from the correlation between the azimuthal angles of p‘s from e+e– annihilation using LEP data • 547 fb-1 charm corrected data sample, • UL and UC double ratios last years: great news from BELLE the Collins FF is being measured in e+e– annihilation, and it is different from zero! measurement of the correlation between the azimuthal angles of p‘s in the near jet and in the far jet from e+e– annihilation F. Bradamante, 6th International Confrence on Perspectives in Hadronic Physics

  37. Collins asymmetries: SUMMARY The facts: • HERMES has measured on a proton targetnon-zero Collins asymmetries for π+ and π- • COMPASS has measured on a deuteron targetCollins asymmetries compatible with zero • BELLE has produced the first results on Collins FF Conclusion: • Collins mechanism is a real phenomenon • universality of Collins FF • transversity can be measured in SIDIS Present picture • Collins:DTu ~ - DTd DT0D(fav.) ~ - DT0D(unfav) To extract TMD DF and FF GLOBAL ANALISYS are necessary F. Bradamante, 6th International Confrence on Perspectives in Hadronic Physics

  38. HERMES, COMPASS, BELLE F. Bradamante, 6th International Confrence on Perspectives in Hadronic Physics

  39. Sivers asymmetry for pions and kaons preliminary 2002-2005 data proton (DIS07) CERN-PH-EP/2008-002hep-ex/0802.2160 (PRL) 2003-2004 data deuteron F. Bradamante, 6th International Confrence on Perspectives in Hadronic Physics

  40. F. Bradamante, 6th International Confrence on Perspectives in Hadronic Physics

  41. Sivers asymmetry the measured asymmetry on deuteron compatible with zero has been interpreted as Evidence for the Absence of Gluon Orbital Angular Momentum in the Nucleon S.J. Brodsky and S. Gardner, PLB643 (2006) 22 F. Bradamante, 6th International Confrence on Perspectives in Hadronic Physics

  42. SUMMARY AND OUTLOOK • a technically challenging new experiment is IN OPERATION SINCE 2002 • a privileged situation at CERN • MANY PHYSICS RESULTS have been producedMANY MORE IN THE PIPE-LINE • COMPASS is foreseen to run up to the end of the present mid-term plan of CERN (2010) BIG DISCOVERY POTENTIAL • with some upgrade COMPASS might be an interesting option even in the second decade of this century F. Bradamante, 6th International Confrence on Perspectives in Hadronic Physics

  43. F. Bradamante, 6th International Confrence on Perspectives in Hadronic Physics

  44. SPARE SLIDES F. Bradamante, 6th International Confrence on Perspectives in Hadronic Physics

  45. Transversity: two hadrons - 1 F. Bradamante, 6th International Confrence on Perspectives in Hadronic Physics

  46. Transversity: two hadrons - 2 all +/- combinations • precise measurement of few % • systematics seems well under control • also compatible with zero • interesting to see proton in 2006 F. Bradamante, 6th International Confrence on Perspectives in Hadronic Physics

  47. Exclusive ρ0production F. Bradamante, 6th International Confrence on Perspectives in Hadronic Physics

  48. Exclusive ρ0production(2002 data) - 1 F. Bradamante, 6th International Confrence on Perspectives in Hadronic Physics

  49. 0.01 < Q² < 0.05 < Q² < 0.3 < Q² < 0.6 < Q² < 2.0 < Q² 0.01 < Q² < 0.05 < Q² < 0.3 < Q² < 0.6 < Q² < 2.0 < Q² < 10 GeV2 Exclusive ρ0production- 2 ANGULAR DISTRIBUTIONS preliminary, statistical errors only, limited by MC corrected for acceptance, smearing and efficiency (MC:DIPSI gen) background not subtracted F. Bradamante, 6th International Confrence on Perspectives in Hadronic Physics

  50. 0.01 < Q² < 0.05 < Q² < 0.3 < Q² < 0.6 < Q² < 2.0 < Q² < 10 GeV2 2002 Exclusive ρ0production - 3 measurement of r 04 00 distribution : Spin density matrix element: Tλρλγare helicity amplitudes meson photon F. Bradamante, 6th International Confrence on Perspectives in Hadronic Physics

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