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Joint Meeting of Pacific Region Particle Physics Communities (DPF2006+JPS200)

Joint Meeting of Pacific Region Particle Physics Communities (DPF2006+JPS200) 200 6.Oct.29-Nov.03, Honolulu, Hawaii , USA. Study of spin structure of nucleon in COMPASS - Upgrade of the polarized target and the spectrometer of COMPASS -.

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Joint Meeting of Pacific Region Particle Physics Communities (DPF2006+JPS200)

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  1. Joint Meeting of Pacific Region Particle Physics Communities (DPF2006+JPS200) 2006.Oct.29-Nov.03, Honolulu, Hawaii , USA Study of spin structure of nucleon in COMPASS- Upgrade of the polarized target and the spectrometer of COMPASS - T. Iwata (Yamagata), N.Doshita(Bochum), S.Horikawa(CERN), N.Horikawa(Chubu), K.Kondo(Bochum), T.Hasegawa(Miyazaki), S.Ishimoto(KEK), T.Matsuda(Miyazaki), on behalf of COMPASS collaboration

  2. Outline Physics programs of COMPASS Experimental apparatus Upgrade of polarized target Upgrade of RICH Summary

  3. Physics programs of COMPASS • Study of nucleon spin structure • with pol. muon beam + pol. nucleon target • physics programs • gluon spin contribution • polarized quark distributions: Dq(x) • transversity : DTq(x) ) • flavor decomposition of Dq(x) and DTq(x) • polarized fragmentation functions • (* Hadron spectroscopy with hadron beams) K.Kondo’s talk semi-inclusive measurements: muons +hadrons T.Matsuda’s talk

  4. COMPASS setup Muon filter 2 MWPCs ECal2 & Hcal2 ~50m SM2 Muonfilter 1 ECal1 & Hcal1 RICH GEM & MWPCs SciFi SM1 GEM & MWPCs Silicon SciFi Scintillating fibers GEM & Straws Micromegas &Drift chambers Polarized Target Beam:polarized m+ 160 GeV 2 . 108 µ/spill (4.8s/16.2s) • Two stages • RICH • High rate trackers • Ecal, Hcal • Muon filter Polarization: mBeam: ~80% 6LiD Target:<50%> m+ beam

  5. COMPASS polarized target 2002 ~ 2004 • Material; 6LiD • 6Li (~ a + D) , D polarized in DNP • High dilution factor: ~ 50% • Twin target cell configuration • to reduce false asym. • pol. reversal by field rotation 3He-4He Dilution Refrigerator Tmin.=50 mK Magnet: 2.5 T solenoid along beam, for DNP 0.5 T dipole transverse to beam for field rotation for transverse pol. aperture: 69 mrad µ beam 69 mrad Mixing chamber Twin target cells 60 cm + 60 cm

  6. Dilution refrigerator Magnet Beam SciFi tracker

  7. Upgrade of PT for 2006

  8. PT Upgrade 1 New magnet with large aperture commissioned in May 2006 been used in physics run hadrons limited by aperture of previous magnet (69 m rad) F ~60cm 180 m rad

  9. Large aperture magnet system

  10. Field homogeneity of the new magnet high polarization in DNP  field homogeneity field homogeneity 30 ppm/ 130cm good enough for DNP

  11. Impact on the physics program • Large increase of hadron acceptance • gluon spin contribution • Open charm events : ~30% gain in statistics • improve precision of gluon polarization • measurements for • polarized parton distributions • transversity • kinematical acceptance extended • high Q2, high x

  12. 3 cell configuration 30cm 60cm 30cm PT Upgrade 2 upstream middle downstream further reduction of false asymmetry by factor ~10

  13. Performance of the new system “frozen spin mode” at 1T in 2006 to avoid stray field effect polarization highest polarization : up: +54.0%, middle: -52.5%, down: +56.0% polarization 0.5% days almost the same performance as the previous system days relaxation time(@1T) ~ 400 days

  14. Upgrade of spectrometer for 2006

  15. Upgrade of spectrometer RICH1 • RICH1: photon detector improvement • Pre-shower detector (RICH wall) installed • More large angle tracking devices • More small area trackers( additional SciFi trackers) RICH wall (pre-shower) DC4

  16. 3 m 6 m vessel mirror wall 5 m photon detectors: CsI MWPC radiator: C4F10 Previous RICH1 • radiator gas: C4F10 • mirror wall: 20 m2 surface • photon-detectors: MWPC(pad read-out) with CsI photocathode • angular acceptance: ±250 mrad horizontal, ±200 mrad vertical • read-out: 83,000 channels (pixels)

  17. RICH1Upgrade • motivation • large uncorrelated background • memory of MWPC + read-out(3 ms) + beam halo • point; slow RICH  fast RICH • Inner part (25%) • Multi Anode PMTs (MAPMT) • excellent timing, no dead time, improved efficiency • Outer part (75%) • new read-out system (APV chip) • time resolution (MWPC + r.o.): 3 ms  < 400 ns

  18. PMT system ¼ of inner part photons field lens concentrator MAPMT field lenses MAPMT inner part : 576 MAPMTs with indiv. telescope Read-out : 9216 ch analogue: MAD4 chip ( upto 1MHz/ch) timig: high resolution TDC, F1 chip HAMAMATSU R7600-M16-03, 16 ch

  19. Performance of upgraded RICH upgraded RICH mass spectrum p K previoussystem upgraded RICH inner part only K: upper limit 43  50 GeV/c previous system

  20. Whole upgrade impacts • Increase of hadron acceptance • Particle IDdeveloped • eg: open charm • ( expected in 2006) • new PT magnet • RICH upgrade; • additional channel in Ecal • gain factor x 2.34 • beam eff. x 0.88 • total x 2.06 w.r.t. 2004 D* yield Estimate 06 04 03 total 2002 /year

  21. Summary • COMPASS aims to study nucleon spin structure • with pol. muon beam and pol. nucleon target. • Important improvements have been performed in PT and RICH. • A large hadron acceptance was obtained with the new PT magnet. • Capability of particle identification has been developed • by the upgraded RICH. • These are essetntial to accomplish the physics programs.

  22. END of TALK Thank you for your attention.

  23. Backup slides

  24. COMPASS Collaboration at CERN More than 220 physicists from 30 Institutes from 12 countries Bielefeld, Bochum, Bonn (ISKP & PI), Erlangen, Freiburg, Heidelberg, Mainz, München (LMU & TU) Дубна (LPP and LNP), Москва (INR, LPI, State University), . Протвино CERN Helsinki Warsawa (SINS), Warsawa (TU) Nagoya/Chubu/Yamagata Miyazaki/KEK Saclay Praha Lisboa Torino (University,INFN), Trieste (University,INFN) Burdwan, Calcutta Tel Aviv

  25. gluon spin contribution gluon polarization Photon Gluon Fusion pQCD • Identification of PGF • q=cOpen charm：detection of D*/D0 , PID essential • q=u,d,s:　select high PThadron pairto reduce B.G.

  26. PGFvia Open Charm Open charm well understood by PGF No physical background ! fragment into charm hadrons detect in Golden channel accidental combination of Kp background D* tagging by to reduce background

  27. Charm ID with RICH1 Cuts • No decay vertex reconstruction • Kaon identification with RICH K p invariant mass spectra Need further improvement of S/BG

  28. outer part • CsI photocathode + MWPC(pad readout) • new electronics for readout • analogue pipe line • fast time response (s < 400 ns) APV chip

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