Slide 1

F.-H. Heinsius (Universitt Freiburg/CERN) Introduction Gluon polarization in the nucleon Transverse spin distribution Newest Results from the Experiment Graduiertenkolleg Freiburg, 24.5.2006 Slide 2 Fritz-Herbert Heinsius GK Freiburg 2006 Towards understanding nonperturbative QCD Nucleon is fundamental in understanding QCD confinement asymptotic freedom spontaneous chiral symmetry breaking Mass around us mostly due to nucleons quark mass accounts for only about 1% mostly due to dynamics of gluons and quarks Do we understand the structure of baryons? measurements unpolarized: 40% of momentum: gluons DIS polarized: 30% of helicity: quarks cannot be calculated from QCD (yet) lattice gauge calculation Study of special bound states: double charmed baryons: 2 heavy & 1 light quark hybrids: q q & gluon glueballs: gluon bound state allowed by QCD, but do they exist? Study QCD at the low energy end using chiral perturbation theory: light meson sector: polarisability of and K Slide 3 Fritz-Herbert Heinsius GK Freiburg 2006 Deep Inelastic Scattering Probing the content of the proton 1968 Friedman, Kendall, Taylor: Nobel prize 1990 DESY: highest Q no further substructure Q = negative momentum transfer squared Slide 4 Fritz-Herbert Heinsius GK Freiburg 2006 Structure Functions parton carries all momentum parton carries 1/3 of momentum gluon contribution reduces momentum carried by quarks including sea quarks x = momentum fraction of the nucleon carried by the parton Slide 5 Fritz-Herbert Heinsius GK Freiburg 2006 Parton Density Distributions 40% of the momentum carried by gluons Slide 6 Fritz-Herbert Heinsius GK Freiburg 2006 Towards understanding nonperturbative QCD Nucleon is fundamental in understanding QCD confinement asymptotic freedom spontaneous chiral symmetry breaking Mass around us mostly due to nucleons quark mass accounts for only about 1% mostly due to dynamics of gluons and quarks Do we understand the structure of baryons? measurements unpolarized: 40% of momentum: gluons polarized: 30% of helicity: quarks cannot be calculated from QCD (yet) lattice gauge calculation Study of special bound states: double charmed baryons: 2 heavy & 1 light quark hybrids: q q & gluon glueballs: gluon bound state allowed by QCD, but do they exist? Study QCD at the low energy end using chiral perturbation theory: light meson sector: polarisability of and K Slide 7 Fritz-Herbert Heinsius GK Freiburg 2006 COMPASS SPS LHC COMPASS: A Facility to study QCD p, or /K beam 230 physicists, 10 countries, 25 institutes Slide 8 Fritz-Herbert Heinsius GK Freiburg 2006 COMPASS: A Facility to study QCD Experiments with muon beam Gluon polarization G/G in the nucleon Flavor dependent quark helicity density distributions q Transverse quark spin distribution functions h 1 (x) Spin transfer in -hyperon production Vector meson production Generalised parton distributions Experiments with hadron beams Pion and kaon polarizabilities Diffractive production of exotic states Search for glueballs Light meson spectroscopy Production of double charmed baryons Application and test of perturbative QCD nonperturbative QCD effective theories chiral perturbation theory lattice QCD Slide 9 Fritz-Herbert Heinsius GK Freiburg 2006 The COMPASS SpectrometerSM1 SM2 RICH ECal & HCal Filter Trigger-hodoscopes Silicon Micromegas SciFi GEMs Drift chambers Straws MWPC Two stage spectrometer Polarized beam and target ~80% 50% SAT,LAT,PID 10 -5 Fritz-Herbert Heinsius GK Freiburg 2006 G/G from Open Charm (D-mesons) Photon gluon fusion N D z D > 0.2 (0.25 for D 0 ) |cos *| < 0.85 (0.5 for D 0 ) RICH identification for K 9 GeV/c < p (K ) < 50 GeV/c Slide 19 Fritz-Herbert Heinsius GK Freiburg 2006 m D 0 with D * tagging m D 0 without D * tagging G/G from Open Charm (D-mesons) 2002 - 2004 2 13 (GeV/c) 2 Slide 20 Fritz-Herbert Heinsius GK Freiburg 2006 G/G from high- p T meson pairs Q 2 > 1 (GeV/c) 2 LEPTO Monte Carlo Photon Gluon Fusion h1h1 h2h2 N Q 2 < 1 (GeV/c) 2 PYTHIA Monte Carlo Slide 21 Fritz-Herbert Heinsius GK Freiburg 2006 How to get G/G Q 2 >1 (GeV/c) 2 Photon Gluon Fusion QCD-Compton Leading Order fractions of cross section determined by Monte Carlo Slide 22 Fritz-Herbert Heinsius GK Freiburg 2006 G/G from high- p T meson pairs G/G = 0.06 0.31 stat. 0.06 syst. Q 2 > 1 (GeV/c) 2 LEPTO Monte Carlo at = 0.13 0.08 2002/2003 Photon Gluon Fusion h1h1 h2h2 N Slide 23 Fritz-Herbert Heinsius GK Freiburg 2006 Background for Q 2Slide 24 Fritz-Herbert Heinsius GK Freiburg 2006 Uncertainty due to the unknown spin distribution in the hadronic structure of the photon Background for Q 2Slide 25 Fritz-Herbert Heinsius GK Freiburg 2006 Monte Carlo Tuning scrutinize systematic error: 15 independent simulations map the parameter space, i.e. for k T in nucleon and photon Fragmentation functions parton shower on/off, renormalization scale Nucleon Photon Slide 26 Fritz-Herbert Heinsius GK Freiburg 2006 G/G from high- p T meson pairs G/G = 0.06 0.31 stat. 0.06 syst. Q 2 > 1 (GeV/c) 2 LEPTO Monte Carlo at = 0.13 0.08 2002/2003 Photon Gluon Fusion h1h1 h2h2 N G/G = 0.016 0.058 stat. 0.055 syst. Q 2 < 1 (GeV/c) 2 PYTHIA Monte Carlo at = 0.085 2002-2004 +0.071 - 0.035 Slide 27 Fritz-Herbert Heinsius GK Freiburg 2006 G/G summary GRSV: Glck et al.,Phys. Rev. D63 (2001) 094005 G=2.5 G=0.6 G=0.2 NLO fits to g 1 2 = 3 Gev 2 Slide 28 Fritz-Herbert Heinsius GK Freiburg 2006 Transverse Spin Distributions 3 independent structure functions are necessary to describe the spin structure of the nucleon at leading order: All of equal importance ! h 1 (x) decouples from leading twist DIS because helicity of quark must flip No mixture with Gluon Slide 29 Fritz-Herbert Heinsius GK Freiburg 2006 3 possible quark polarimeters suggested: Azimuthal distribution of hadrons Azimuthal dependence of the plane containing 2 hadrons Measure transverse polarization of COMPASS studies all of them S = azimuthal angle of target spin vector after scattering h = azimuthal angle of hadron C = h - S h Transverse Spin Physics muon beam transverse target polarisation Slide 30 Fritz-Herbert Heinsius GK Freiburg 2006 Azimuthal distribution of hadrons Transverse Spin Physics Collins: spin dependent fragmentation of transversely polarised quarks into hadrons Efremov, Goeke, Scheitzer, hep-ph/060354 (fit to BELLE & HERMES data) Slide 31 Fritz-Herbert Heinsius GK Freiburg 2006 Transverse Spin Physics Collins fragmentation function extracted from HERMES / BELLE From: Efremov, Goeke, Schweitzer hep-ph/0603054 COMPASS 2002 data compatible with fit deuteron essential to determine h 1 d Slide 32 Fritz-Herbert Heinsius GK Freiburg 2006 Azimuthal distribution of hadrons Transverse Spin Physics Efremov, Goeke, Scheitzer, hep-ph/060354 (fit to BELLE & HERMES data) Anselmino et. al hep-ph/0507181 Sivers : intrinsic k T dependence of the quark distribution Slide 33 Fritz-Herbert Heinsius GK Freiburg 2006 Azimuthal dependence of the plane containing 2 hadrons Transverse Spin Physics precise measurement of few % systematics seems well under control also compatible with zero interesting to see proton in 2006 1 +/- combination per event: p t ordering all +/- combination per event Slide 34 Fritz-Herbert Heinsius GK Freiburg 2006 Measure transverse polarization of Transverse Spin Physics Slide 35 Fritz-Herbert Heinsius GK Freiburg 2006 Results not covered semi-inclusive asymmetries, single hadron high-p T spin-density matrix elements polarisation pentaquark search diffractive processes J/ production (1530) 0 Slide 36 Fritz-Herbert Heinsius GK Freiburg 2006 COMPASS upgrades for this year New solenoid magnet Larger acceptance 70 mrad 180 mrad RICH upgrade Central region: MAPMT system Outer region: new faster electronics Other upgrades: Large Drift Chamber ECAL1 Slide 37 Fritz-Herbert Heinsius GK Freiburg 2006 Summary / Outlook COMPASS results (2002-2004) polarisation of gluons in the nucleon transversity: small asymmetries on deuteron Many more results not covered Major upgrade of spectrometer for this year Next year: start spectroscopy hybrids, glueballs, Long term future (2010+): generalised parton distributions (DVCS,)