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The PHOTON BALL at COSY

beam. The PHOTON BALL at COSY. W.Döring, M.Hoek, R.Novotny II.Physics Institute, University Giessen, Germany M.Büscher, V.Hejny, H.R.Koch, H.Machner, H.Seyfarth, H.Ströher Nuclear Physics Institute, FZ Jülich, Germany J.Bacelar, H.Löhner KVI, Groningen, The Netherlands V.Chernyshev

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The PHOTON BALL at COSY

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  1. beam The PHOTON BALL at COSY W.Döring, M.Hoek, R.Novotny II.Physics Institute, University Giessen, Germany M.Büscher, V.Hejny, H.R.Koch, H.Machner, H.Seyfarth, H.Ströher Nuclear Physics Institute, FZ Jülich, Germany J.Bacelar, H.Löhner KVI, Groningen, The Netherlands V.Chernyshev Institute for Theoretical and Experimental Physics, Moscow, Russia A.Wronska Institute of Physics, Cracow, Poland • physics motivation ANKE@COSY • experimental requirements • the concept • status on R&D • photon and particle detection with PbWO4 • read-out with fine-mesh phototubes • outlook CALOR 2002, Pasadena

  2. The Cooler SynchrotronCOSY @ FZ Jülich acceleration of protons and deuterons beam momentum p < 3.5 GeV/c internal and external experiments luminosity  10 32 cm-2s-1 polarized beams Apparatus for studies of Nucleon and Kaon Ejectiles

  3. the magnetic spectrometer • 3 C-shaped dipoles • ramped synchronously • with COSY • detection and identification of • charged particles • indirect detection of short-lived • neutral particles: • missing mass analysis • the physics programm • study of the structure • of the nucleon • interactions of nucleons • meson production in • nN and NN collisions ANKE

  4. direct measurement of neutral mesons via the invariant mass of thedecay photons in a new dedicated photon detector ANKE combination of charged and neutral particle detection integration of various target concepts significant background reduction complete set of variables (even for multi-meson events) events kinematically overdetermined

  5. technical constraints gg-coincidences good time resolution photomultiplier read-out charged-particle veto plastic scintillator array invariant mass analysis good energy resolution (12X0 ) high granularity large solid angle ~4p limited space in the target region compact design dense and fast detector material integration of different targets and detectors flexible geometry, modularity magnetic stray-field (~ 0.2T) fine-mesh phototubes PbWO4

  6. design concept 540 mm PbWO4 0.5 m 120 mm the individual crystal module different geometries 11 maximum dimensions of rear surface < 43 mm total number876 120 mm =13.5X0 energy range 0 - 2 GeV s (t) ~ 130 ps s (E = 1GeV) ~ 3.5% solid angle 93% of 4p R 5505 PbWO4 soft iron cylinder thickness 3mm quartz light guide

  7. photon response < 1GeV: PbWO4 Eg=45.4 MeV Eg=105.6 MeV s/E=7.4% s/E=5.3% counts energy / a.u. energy resolution for electromagnetic probes for PbWO4

  8. experimental tests of charged particle response @COSY 5x5 matrix target TOF start detector µ measurement: energy, TOF of charged reaction products particle ID (p+/-, p, d, t, e+/-) energy response 1.2 GeV p + Al

  9. experimental tests of charged particle response @COSY Ep= 50 MeV Ep= 200 MeV p p counts p d d t energy / MeV “proton calibration” t d time-of-flight relative to photons / ns p p MIP deposited energy / MeV

  10. experimental tests of charged particle response @COSY g “proton calibration” p „proton-calibration“ fails! K p MIP d deposited energy / MeV quenching effects ? p / p ~ 3 / 1

  11. experimental tests of charged particle response @ KVI measurement: energy of scattered protons energy response of BaF2, CeF3 and PWO 85 MeV p + C, CH2

  12. experimental tests of charged particle response @ KVI counts counts proton energy / MeV proton energy / MeV CeF3BaF2 PWO PWO:Mo comparison: 85 MeV p + C 85 MeV p + CH2

  13. experimental tests of charged particle response @ KVI PWO PWO:Mo CeF3 BaF2 achieved energy resolutions E < 100 MeV

  14. read-out in magnetic field: fine-mesh phototubes optional shielding R5505 test in static magnetic field Hamamatsu R 5505  25mm 15 stages gain: 5105@ 0Tesla blue LED 3mm soft iron shielding will be sufficient

  15. read-out in magnetic field: fine-mesh phototubes acceleration phase ramping of D2: up to 1.6 Tesla PM signal [a.u.] operation time [D t =1s] operation time [D t = 0.01s] measured in ANKE environment

  16. first test with prototypes: photon response new crystals: 32 mm2 PWO 120 mm 54.6MeV 105.6MeV 77.7MeV 152.7MeV 200.2MeV 250.6MeV 457.5 MeV 3x3 array 740.5MeV read-out R 5505 measurement with energy marked photons at MAMI, Mainz counts energy (a.u.)

  17. first test with prototypes: photon response 3x3 array no difference due to quartz light guide read-out R 5505 perfect linearity good energy resolution

  18. outlook and conclusions additional R&D: PM base:Cockroft-Walton generators read-out electronics:adapted TAPS electronics VME-based, 8-ch/board trigger electronics:multiplicity trigger pattern recognition detector mechanics:modular and flexible short installation time time schedule: summer 2002 detector design to be fixed 2002/03 support structure, delivery of crystals and phototubes end of 2004 installation at ANKE first experimentsh and w production in pp and pn collisions

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