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COMPASS Status Report 2009/2010

COMPASS Status Report 2009/2010. Bernhard Ketzer Technische Universit ät München for the COMPASS Collaboration SPSC, CERN 29 June 2010. Outline. New results from 2004 p - pilot run New results from 2008 hadron run 3 p final states Multi-particle final states (>3)

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COMPASS Status Report 2009/2010

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  1. COMPASS Status Report2009/2010 Bernhard Ketzer TechnischeUniversität München forthe COMPASS Collaboration SPSC, CERN 29 June 2010

  2. Outline • New results from 2004 p- pilot run • New results from 2008 hadron run • 3p final states • Multi-particle final states (>3) • Kaonic final states • Data with proton beam • Hadron run 2009 • Performance of spectrometer • First analysis of data • New results from muon scattering • Helicity distributions • Collins and Sivers asymmetries • Update on DG from open charm • Preparation and status of 2010 muon run

  3. The COMPASS Experiment MuonWall SM2 E/HCAL E/HCAL MuonWall SM1 Target RICH Beam • Two-stage spectrometer • large angular acceptance • broad kinematical range • ~250000 channels • > 1000 TB/year 50 m • Data taking periods: • 2002-2004: 160 GeV/c m+ • 2004: 2 weeks 190 GeV/c p- • 2006-2007: 160 GeV/c m+ • 2008-2009: 190 GeV/c p- • 2010: 160 GeV/c m+ RPD [COMPASS, P. Abbon et al., NIM A 577, 455 (2007)]

  4. Hadron Reactions at COMPASS Three production mechanisms studied in parallel usingproton, pionandkaonprojectiles Central production Diffractive dissociation Photoproduction • Rapidity gap between pslow, hfast, X • Beam particle looses ~10% of its energy • Particles at large angles from X decays • Possible source of glueballs (DPE) • Forward kinematics • Need to separate particles at • very small angles • Study of JPC-exotic mesons

  5. Analysis of 2004 Data Beam: 190 GeV/c p-, 5·106pps Target: 3 mm Pb Trigger: Multiplicity • Analysis: • p-p-p+ final state • High-t’: observation of spin-exotic resonance with JPC=1-+ • Low-t’: new results on photoproduction / diffraction • p-p-p-p+p+final state • acceptance corrections done • optimization of wave set ongoing

  6. JPC=1-+ Exotic Wave in p-p-p+

  7. p-p-p+ Final State at low t’ • Coherent production on Pb nucleus • Contributions at very low t’: • Diffraction: • Photoprod.: • Fit of 2 exponentialsfor t’ < 0.006 GeV2/c2 • Steep fall-off for photoproduced events dominated by experimental resolution • Statistical subtraction of diffractive contribution

  8. Partial Wave Analysis Two clearly separated regions: t’ < 0.5·10-3GeV2/c2 0.0015 < t’ < 0.01 GeV2/c2 a2(1320) (M=1) present in both t’-ranges  different production mechanisms? Diffraction vanishes for t’→0 Photoproduction Phase difference a2(1320) - a1(1260): offset for two t’-regions!

  9. Phase Difference a2-a1 PWA in t’ bins for single mass bin 1.26 < m3p < 1.38 GeV/c2 (a2 region) Theory [G. Faeldt et al., Phys. Rev. C 79 014607 (2009)] Plot by N. Kaiser, TUM Experiment F(a2) F(a1) DF(a2-a1) • smooth transitionbetween a2photoproduction • todiffractiveproductionwithincreasing t‘ • possibilitytocleanlyseparate photoproductionfromdiffraction  determinationofradiativewidthof a2(1320), p2(1670)

  10. Analysis of 2008 Data Beam: 190 GeV/c p-, 2.5·107pps, protons Target: 40 cm liquid hydrogen Trigger: Recoil proton (DT0) • Analysis: • p-p-p+ final state • full 2008 statistics available • M=1 production suppressed • acceptance corrections being finalized (MC description) • final states containing neutral particles • ECAL optimization close to being finished • p-p0p0 final state:isospin symmetry • other states • kaonic final states

  11. p-p-p+ Final State • Full 2008 statistics available: 96M events in high-t’, 5.8M a2(1320) • M=1 production on H suppressed compared to Pb • Acceptance corrections being finalized (MC description) • Wave set being optimized

  12. p-p0p0 Final State • Partial 2008 statistics, no acceptance correction • Normalization to a2(1320) intensity • Charged and neutral mode rely on different detectors  systematics • Isospinsymmetry • expect same intensity for isovector isobars (e.g. r) • expect half the intensity in neutral mode for isoscalar isobars (f0, f2) • acceptance being finalized, ECAL reconstruction being optimized

  13. Multi-Particle (>3) Final States • Motivation: • Higher masses accessible  many disputed states: 0-+, 1++, 2-+,... • p1(1400) observed in hp • p1(1600) observed in h’p, b1p, f1p • p1(2000) observed in b1p, f1p • JPC=1-+ hybrid decay modes • [Page, Swanson, Szczepaniak, PRD 59, 034016 (1999)] established need confirmation further states

  14. p-h Final State p-p+p0 invariant mass gg invariant mass h w Select Select a2(1320)  PWA requiredtoresolvesmallcontributions, e.g. p1(1400)

  15. p-p-p+h Final State p -p +h invariant mass f1(1285) f1(1285) h’ h’ Select Hybrid p1(1600) expected in this channel

  16. p-hh Final State COMPASS 53% of 2008 data No cut for central production applied  both diffractively and centrally produced states

  17. Kaonic Final States • Access to exotics, glueballs • Clarify flavor content and structure of resonance • Expand knowledge on kaon spectrum • Requires CEDAR & RICH PID • Channels: Diffractive states at 1.7 GeV/c2 and 2.2 GeV/c2, decaying to K*(892)

  18. Kaonic Final States Diffractive dissociation:   • >10 × BNL statistics • very clean spectrum • possibly also f1(1420) seen

  19. Data with Proton Beam • Only very short test in 2008 (early shutdown of North Area): • Beam: 190 GeV/c, 71.5% p, 25.5% p, 3.0% K • CEDARs tagging protons • Trigger: Recoil proton • ~10% of total 2008/2009 statistics • Baryon spectroscopy: • Central Production

  20. Baryon Spectroscopy

  21. Central Production • cut on

  22. Hadron Run 2009 • Goals: • collect data sample with positive beam on lH2 target (central production) • increase data sample with negative beam on lH2 target (central production) • complete data taking with negative beam on lH2 target (diffr., low-t) • take data with negative beam on nuclear targets (M-dep., statistics) • PS/SPS efficiency ~70% rather than 80% as assumed for request • lower data taking efficiency for COMPASS for low-t’ and ECAL trigger

  23. New Equipment for 2009 Run Silicon Microstrip Detectors: all five stations at 200K, stability < 1K ECAL2 upgrade: Pipelined readout completed (1000 ch. MSADC) ECAL1 monitoring: LED replaced by laser system Nuclear targets: Pb, W, Ni • New trigger elements: • Multiplicity trigger • Digital trigger for ECAL

  24. Trigger Diffractive TriggerDT0= BT  RPD  !Veto  high-t’: t’>0.07 GeV2/c2 • Multiplicity Trigger: Cover full range of t’ • 12 trapezoidal scintillator slabs, ø 62 cm • central disk scintillator with 83 cm air light guide • acceptance 180 mrad • LT1 = [≥ 1(2) outer slabs]  BT  !Veto • LT3 = [> 1.6(2.5) MIPS disk]  BT  !Veto • Digital Trigger for ECAL: high-energy photons • Implemented in existing FPGA of MSADC • Time and amplitude extraction for each cell • Prim = Esum(12×12 cells) > Ethr(50/70 GeV) • Efficiency > 98%, energy resolution = 3.3 GeV • Time resolution 0.8 ns

  25. Nuclear Targets • Goals: • study dependence of M-population on A • increase statistics on nuclear targets • Target holder: carbon fiber / fiber glass • Thin disks of Pb, W, Ni: 25-250 mm

  26. First Look at 2009 Data Nuclear Targets: p-p-p+ final state 2009: 8.1M events 3 × statistics of 2004 2009: 2.3M events 6 × statistics of 2004

  27. Conclusions on Hadron Analysis • Very high statistics, 10 – 200 × existing data sample • Many new channels being analyzed

  28. Conclusions on Hadron Analysis • Very high statistics, 10 – 200 × existing data sample • Many new channels being analyzed • Monte Carlo  acceptance corrections • very good description of setup necessary (no asymmetries!) • new hardware (2008/2009) implemented • very large data samples required • Calorimetry: • improvement & unification of reconstruction code (ECAL1/ECAL2) • calibration: electron beam + Laser/LED + p0 signal • PWA: • three different programs • careful selection of wave set for PWA due to small statistical errors • combined PWA of diffractive and central production • new formalism for baryonic resonances • new international task PWA force: COMPASS, JLAB, PANDA, …

  29. Conclusions on Hadron Analysis • Future data taking: based on results of ongoing analyses • Higher beam energies for cleaner separation of central production • All neutral final states with full ECAL trigger • Primakoff measurements with p-, p+, K  Addendum to COMPASS II Proposal

  30. New Results with Muon Beam • Muon beam 2007 with NH3 target: • Helicity distributions • Collins and Sivers asymmetries Gluon polarisation from open charm (2002-2007 data) Longitudinal spin transfer to L and Lbar in polarised DIS

  31. Helicity Distributions Longitudinal spin asymmetry: • Pb ≈ -80% • Pt ≈ 90% • f = 0.1-0.2 • improved precision of at low x • Q2[1,100] GeV2 • no Q2 dependence of A1 • data compatible with g1=const. • for x→0.004 [COMPASS, M.Alekseev et al., Phys. Lett. B 690, 466 (2010)]

  32. Bjorken Sum Rule Non-singlet spin structure function • Q2 evolution independent of singlet quark • and gluon densities • both g1p and g1n measured at COMPASS • 3-parameter NLO QCD fit 1st moment  Bjorken sum rule • ~92% of G1NS from measured region • saturation of integral only at lowest x 

  33. Collins Asymmetry Fragmentation of transversely polarised quarks to unpolarised hadrons Comparison with HERMES  COMPASS data with x>0.050

  34. Sivers Asymmetry Modulation of transverse momentum of unpolarisedquarks in a transversely polarised nucleon Comparison with HERMES  COMPASS data with x>0.032

  35. Gluon Polarisation from Open Charm p0 (2002-2007 data)

  36. Muon Run 2010 H1 hodoscope Pixel- Gem PA03-05 MWPC Polarized Target Cold Silicon SciFi 15 MM cooling H2 hodoscope

  37. Muon Run 2010 • Triggers: • (modified) 2007 triggers fully operational • Two new hodoscopes (H1, H2) not yet ready Installation: May 21 May 20

  38. Muon Run 2010 • Triggers: • (modified) 2007 triggers fully operational • Two new hodoscopes (H1, H2) not yet ready • to be operational by end of July 2007 June 10, 2010 • Polarized target: operational • Upgrade of control system for liq. 4He delivery system • New control system for new 4He pumps for cryogenic operation • Modification of cooling water infrastructure 24 h

  39. Muon Run 2010 • Triggers: • (modified) 2007 triggers fully operational • Two new hodoscopes (H1, H2) not yet ready • to be operational by end of July Polarized target: operational Detectors: all operational Physics data taking with transversely polarized target: started June 12

  40. Publications • Since 2009 status report: • Measurement of the Longitudinal Spin Transfer to Λ and Λ-bar Hyperons • in Polarized Muon DIS, Euro. Phys. J. C 64, 171 (2009). • Observation of a JPC = 1–+ exotic resonance in diffractive dissociation • of 190 GeV/c π– into π–π–π+, Phys. Rev. Lett. 104, 241803 (2010). • The spin-dependent structure function of the proton g1p and a Test • of the Bjorken Sum Rule, Phys. Lett. B 690, 466 (2010). • Measurement of the Collins and Sivers asymmetries on transversely • polarised protons, submitted to Phys. Lett. B (2010), 1005.5609v1 [hep-ex].

  41. Conferences & Workshops • 2009: 91 COMPASS presentations • DIS2009: 9 talks • CIPANP 2009: 4 talks • HEP 2009: 3 talks • HADRON 2009: 9 talks • 2010: >20 COMPASS presentations • DIS 2010: 10 talks • MENU 2010: 3 talks • MESON 2010: 3 talks • QCD 2010: 3 talks

  42. Spare Slides

  43. Longitudinal Spin Transfer to L and L • Polarisedm (-0.80) DIS on unpolarised target (2003-2004): • Q2>1 GeV2/c2 • Fractional virtual photon • energy 0.2 < y < 0.9 • 30·107 DIS events  Spin transfer to L small (compatible with 0)  Spin transfer to L 0.4-0.5

  44. Flavor Separation • Longitudinal spin asymmetries • for identified pions and kaons in • SIDIS on NH3 target • combined with data on d and inclusive DIS • LO QCD analysis • Ds, Dsbar compatible with 0 • sea quark distributions small • no sizable x-dependence

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