PHYSICS RESULTS FROM COMPASS F. Bradamante University of Trieste and INFN Trieste on behalf of the Collaboration Workshop on Hadron Structure at J-PARC November 30, 2005

F. Bradamante, Workshop on Hadron Structure, J-PARC COmmon Muon and Proton Apparatus for Structure and 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, Workshop on Hadron Structure, J-PARC Physics program of COMPASS Experiments with muon beam ΔG/G g 1 Transverse spin effects Flavor decomposition of spin distribution functions Vector meson production Spin transfer in  Λ-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

F. Bradamante, Workshop on Hadron Structure, J-PARC N SPS LHC luminosity: ~ cm -2 s -1 beam intensity: µ +/spill (4.8s/16.2s) beam momentum: 160 GeV/c longitudinally polarised muon beam longitudinally or transversely polarised target calorimetry particle identification

F. Bradamante, Workshop on Hadron Structure, J-PARC The Spectrometer SM1SM2 6 LiD Target 160 GeV μ RICH ECal & HCal μ Filter Trigger-hodoscopes Silicon Micromegas SciFi Gems Drift chambers Straws MWPC TWO STAGE SPECTROMETER: Polarized beam and target SAT,LAT,PID < x < < Q 2 < 10 GeV 2 50 m

F. Bradamante, Workshop on Hadron Structure, J-PARC WHERE ARE WE ? in 2002, 2003, and 2004 COMPASS has taken data in the muon program configuration physics results 1.  G/G 2.  3. Transversity 4. Pentaquark 5. Exclusive ρ 0 6. Λ physics pilot run in 2004 for hadron program 3·10 10 events ~ 1000 TB 160 GeV, polarized  beam 6 LiD polarized target (~polarized deuterons) 2005: no beam

F. Bradamante, Workshop on Hadron Structure, J-PARC physics results ΔG/G

F. Bradamante, Workshop on Hadron Structure, J-PARC  G/G at COMPASS Photon Gluon Fusion N q = c cross section difference in charmed meson production → theory well understood → experiment challenging q = u,d,s cross section difference in 2+1 jet production in COMPASS: events with 2 hadrons with high-p t → experiment easy → theory more difficult

F. Bradamante, Workshop on Hadron Structure, J-PARC ΔG/G from Open Charm

F. Bradamante, Workshop on Hadron Structure, J-PARC M K  - M D 0 (PDG) [MeV/c 2 ] M K  - (M K  + M  ) [MeV/c 2 ] ΔG/G from Open Charm - 1 M K  - (M K  + M  ) (MeV) D* (2002) M K  - (M K  + M  ) [MeV/c 2 ]

F. Bradamante, Workshop on Hadron Structure, J-PARC M K  - M D 0 (PDG) [MeV/c 2 ] M K  - (M K  + M  ) [MeV/c 2 ] M K  - (M K  + M  ) (MeV) D* (2002) M K  - (M K  + M  ) [MeV/c 2 ] D0D0 (2002) M K  - M D 0 (PDG) [MeV/c 2 ] ΔG/G from Open Charm - 2

F. Bradamante, Workshop on Hadron Structure, J-PARC D 0 (2003) 1100 events D 0 (untagged, 2003) 4200 events COMPASS preliminary D 0 (2002) 400 events COMPASS preliminary D 0 (untagged, 2002) 1400 events COMPASS preliminary ΔG/G from Open Charm - 3

F. Bradamante, Workshop on Hadron Structure, J-PARC First measurement of ΔG/G with Open Charm tagging with 2004 data: 0.73  0.43 = 0.15 ±   g x G G ΔG/G from Open Charm - 4

F. Bradamante, Workshop on Hadron Structure, J-PARC ΔG/G from High-p t hadron pairs

F. Bradamante, Workshop on Hadron Structure, J-PARC PGF LO DIS QCD- Compton PGF and background ΔG/G from High-p t hadrons, Q 2 > 1 (GeV/c) 2 - 1

F. Bradamante, Workshop on Hadron Structure, J-PARC ΔG/G from High-p t hadrons, Q 2 > 1 (GeV/c) Data – Monte Carlo (LEPTO) comparison Q2Q2 leading hadron: p leading hadron: p t

F. Bradamante, Workshop on Hadron Structure, J-PARC Results from Monte Carlo: Ratio of PGF events ΔG/G from High-p t hadrons, Q 2 > 1 (GeV/c) with 2004 data: 0.31  0.22 Gluon polarisation

F. Bradamante, Workshop on Hadron Structure, J-PARC PGF LO DIS QCD- Compton all Q 2 ΔG/G from High-p t hadrons

F. Bradamante, Workshop on Hadron Structure, J-PARC PGF LO DIS QCD- Compton low Q 2 all Q 2 resolved photon ΔG/G from High-p t hadrons

F. Bradamante, Workshop on Hadron Structure, J-PARC PGF QCD-C LO DIS qq‘→ qq ‘ qg→ qg gg→ gg low p t direct resolv.  Results from PYTHIA Background as for Q 2 > 1 (GeV/c) 2 additional background from resolved photon events additional processes sensitive to gluons in the nucleon neglect LO DIS and low p t ΔG/G from High-p t hadrons, Q 2 < 1 (GeV/c) 2 - 1

F. Bradamante, Workshop on Hadron Structure, J-PARC Determination of ΔG/G : A LL /D = ± stat. ± syst with 2004 data:  0.06 hep-ex/ , CERN-PH-EP/ , Phys. Lett. B ΔG/G from High-p t hadrons, Q 2 < 1 (GeV/c) 2 - 2

F. Bradamante, Workshop on Hadron Structure, J-PARC  G/G from high-p t : results data results favour small ΔG or ΔG crosses 0 around x g ≈ GRSV2000 with 1  G =  G =  G = 0.2 Glück et al., Phys. Rev. D63 (2001) preliminary hep-ex/ accepted PLB

F. Bradamante, Workshop on Hadron Structure, J-PARC g1dg1dg1dg1d

g 1 of the deuteron ( ) most precise measurement for < x < 0.03 new NLO QCD fit, precision of a 0 improves factor 2 (Q 2 = 4 GeV 2 ) Phys Lett B 612 (2005) 154

F. Bradamante, Workshop on Hadron Structure, J-PARC Transversity single hadron two hadrons Λ

F. Bradamante, Workshop on Hadron Structure, J-PARC Collins and Sivers angles   C =  h -  S’  S =  h -  S  S ’ azimuthal angle of spin vector of fragmenting quark (  S’’ =   -  S )  h azimuthal angle of hadron momentum Transversity – single hadron - 1

F. Bradamante, Workshop on Hadron Structure, J-PARC Transversity – single hadron - 2 first measurements of transverse spin asymmetries in DIS of high energy muons on a transversely polarized deuteron target published single hadron asymmetries from 2002 run Collins: related to transverse quark distributions Sivers: related to intrinsic k T Phys Rev Lett 94 (2005)

F. Bradamante, Workshop on Hadron Structure, J-PARC Transversity: two hadrons - 1

F. Bradamante, Workshop on Hadron Structure, J-PARC Transversity: two hadrons - 2 precise measurement of few % systematics seems well under control also compatible with zero interesting to see proton in 2006 all +/- combinations

F. Bradamante, Workshop on Hadron Structure, J-PARC Transversity: two hadrons data weighted average with h 1 always positive 1 +/- combination per events: p t ordering

F. Bradamante, Workshop on Hadron Structure, J-PARC Transversity: Λ polarization data

F. Bradamante, Workshop on Hadron Structure, J-PARC Pentaquark search

F. Bradamante, Workshop on Hadron Structure, J-PARC motivated by NA49 report of pentaquark candidate COMPASS has large sample of the double-strange Ξ – baryon (18000 Ξ –, Ξ + ) from data search for Ξ – π – resonance Φ(1860) – – → Ξ – π – → Λπ – π – → p π – π – π – Φ(1860) Pentaquark search - 1

F. Bradamante, Workshop on Hadron Structure, J-PARC Φ(1860) Pentaquark search - 2 compare to yields opposite-sign pairs: Ξ(1530) 0 → Ξ – π +, 1700 and 920 evts like-sign pairs: evts <79 and <89 at 99% CL (expected ~400) Ξ(1530) 0 Eur Phys J C41 (2005) 469

F. Bradamante, Workshop on Hadron Structure, J-PARC Exclusive ρ 0 production

F. Bradamante, Workshop on Hadron Structure, J-PARC Exclusive ρ 0 production (2002 data) - 1

F. Bradamante, Workshop on Hadron Structure, J-PARC Exclusive ρ 0 production - 2 ANGULAR DISTRIBUTIONS 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 GeV 2 preliminary, statistical errors only, limited by MC corrected for acceptance, smearing and efficiency (MC:DIPSI gen) background not subtracted

F. Bradamante, Workshop on Hadron Structure, J-PARC measurement of r Exclusive ρ 0 production < Q² < 0.05 < Q² < 0.3 < Q² < 0.6 < Q² < 2.0 < Q² < 10 GeV 2 distribution : Spin density matrix element: T λ ρ λγ are helicity amplitudes meson photon 2002

F. Bradamante, Workshop on Hadron Structure, J-PARC measurement of r and Im r Exclusive ρ 0 production < Q² < 0.05 < Q² < 0.3 < Q² < 0.6 < Q² < 2.0 < Q² < 10 GeV 2 distribution : Spin density matrix element: beam polarisation if SCHC holds weak violation

F. Bradamante, Workshop on Hadron Structure, J-PARC Longitudinal polarization of Λ and antiΛ in DIS

F. Bradamante, Workshop on Hadron Structure, J-PARC Event selection p -- ++ ’+’+ V1V1 V2V2  N(  )N(  ) E NOMAD HERMES COMPASS COMPASS Λ POLARIZATION (2002 data) - 1

F. Bradamante, Workshop on Hadron Structure, J-PARC Λ POLARIZATION 2002 data

F. Bradamante, Workshop on Hadron Structure, J-PARC Λ POLARIZATION 2002 data

F. Bradamante, Workshop on Hadron Structure, J-PARC NEAR FUTURE ( ) Workshop on Future COMPASS Yellow Report CERN , 22 Nov IMPORTANT UPGRADE of the SPECTROMETER ONGOING RICH TRACKING E.M. CALORIMETERS O. D. P.T. MAGNET Veto System 2006 MUON RUNNING 100 days 6LiD Longitudinal Polarization 30 days NH3 Transverse Polarization 2007 HADRON RUNNING CENTRAL PRODUCTION with 300 GeV hadron beam and LH2 target COMPLETE THE APPROVED MUON and HADRON PROGRAMME

F. Bradamante, Workshop on Hadron Structure, J-PARC a technically challenging new experiment is IN OPERATION SINCE 2002 SUMMARY AND OUTLOOK “LHC” technologies detectors read-out data handling FIRST PHYSICS RESULTS have been produced MANY MORE IN THE PIPE-LINE BIG DISCOVERY POTENTIAL a privileged situation at CERN with some upgrade COMPASS might be an interesting option even in the second decade of this century COMPASS is foreseen to run up to the end of the present mid-term plan of CERN (2010)