1. 1 Silvia DALLA TORRE Playa del Carmen, 30/11-5/12/2004 - 5 th RICH Workshop STATUS AND CHARACTERIZATION OF COMPASS RICH-1 on-line image from RICH-1 event display INSTITUTIONS:  Trieste, INFN and University, ICTP  Turin, INFN and University  Bielefeld, University  CERN support OUTLINE:  RICH-1 in COMPASS  recall the main characteristiucs (4 talks in Pylos !) (4 talks in Pylos !)  hardware news  detector performances S. Dalla Torre S. Dalla Torre INFN – TRIESTE on behalf of the COMPASS RICH group Playa del Carmen, 30/11-6/12/2004 - 5 th RICH Workshop

2. 2 Silvia DALLA TORRE Playa del Carmen, 30/11-5/12/2004 - 5 th RICH Workshop With the muon beam * Gluon Polarization  G/G transverse spin distribution functions  T q (x) Flavor dependent polarized quark helicity densities  q(x)  physics Diffractive VM-Production * Data collected COMPASS With hadron beams Primakoff-Reactions * -polarizability of  and K glueballs and hybrids charmed mesons and baryons -semi-leptonic decays -double-charmed baryons understanding the non-perturbative physics of the nucleon

3. 3 Silvia DALLA TORRE Playa del Carmen, 30/11-5/12/2004 - 5 th RICH Workshop SM1 dipole SM2 dipole Polarised Target HCAL1 Muon-filter1,MW1 Micromegas,DC,SciFi Gems,SciFi,DCs,straws MWPC Gems Scifi trigger-hodoscopes Silicon COMPASS SPECTROMETER COMPASS SPECTROMETER RICH_1 BMS Gem_11 ECAL2,HCAL2 straws,MWPC,Gems,SciFi straws Muon-filter2,MW2 DW45 SciFi Veto Beam: 160 GeV µ + 2. 10 8 µ/spill (4.8 s/16.2s) P  ~ 80%

4. 4 Silvia DALLA TORRE Playa del Carmen, 30/11-5/12/2004 - 5 th RICH Workshop COMPASS RICH-1 - DESIGN from the experiment design:  hadron PID up to ~50 GeV/c  LARGE acceptance (large size): H: 500 mrad H: 500 mrad V: 400 mrad V: 400 mrad  able to stand trigger rates up to 100 KHz up to 100 KHz  beam rate up to 10 8 Hz  minimize material + detector designed in 1996 radiator: C 4 F 10 5 m 6 m 3 m photondetectors: CsI MWPC mirrorwall vessel radiator: C 4 F 10 detection of VUV photons (165-200 nm)

5. 5 Silvia DALLA TORRE Playa del Carmen, 30/11-5/12/2004 - 5 th RICH Workshop PHOTON DETECTION photon detectors (PD) : 5.3 m 2 MWPCs (8 chambers) with CsI photocathoderead-out: 84,000 analog read-out ch.s with extended local intelligence MWPCs with CsI photocathodes 2 CsI photocathodes, 60 x 60 cm 2 each

6. 6 Silvia DALLA TORRE Playa del Carmen, 30/11-5/12/2004 - 5 th RICH Workshop photocathodestoring glove box to handlephotocathodes photocathodetransportationsystem MWPCs WITH LARGE SIZE PHOTOCATHODES, COMPASS EXPERIENCE CsI: hygroscopic, water degrades QE never never exposed to air (max 50 ppm O 2, routinely: 10 ppm) marble table with x,y movement and microscope to solde anode wire and for dimensional checks (gaps, planarity within 100  m)

7. 7 Silvia DALLA TORRE Playa del Carmen, 30/11-5/12/2004 - 5 th RICH Workshop PHOTON DETECTORs behaviour in the experiment PHOTON DETECTORs behaviour in the experiment wire defect, diameter 20  m some PDs exhibit electrical instabilities when exposed to radioactive rates (*), LONG RECOVERY TIME ! (~ 1 d) Instabilities related to – local tiny defects 2001 - 2 good PDs / 8 2002 - 5 good PDs / 8 2003, 2004 – segmented HV supply: 97% MWPC surface good 97% MWPC surface good (*) with  beams : MIP flux : ~ 5 x 10 5 / s / m 2 (similar for all PDs) MIP flux : ~ 5 x 10 5 / s / m 2 (similar for all PDs) ph. flux : up to 3 x 10 5 / s / cm 2 ph. flux : up to 3 x 10 5 / s / cm 2

8. 8 Silvia DALLA TORRE Playa del Carmen, 30/11-5/12/2004 - 5 th RICH Workshop RICH-1 mirror system ‘VUV mirror wall’, 21 m 2,116 mirrors radius: 6.6 m average on 126 mirror units at production 2000 = @ COATING reflectance wave length reflectance stable in time 2002 2001 2000

9. 9 Silvia DALLA TORRE Playa del Carmen, 30/11-5/12/2004 - 5 th RICH Workshop MIRROR WALL MECHANICS: light, stiff and adjustable mirror wall mechanics, assembled the elements of this modular structure mirror wall mechanics,assembling assembly jig mirror rear side individual mirror support regulation for angular alignment, 2 orthog. movements THICKNESS mechanics: 2.5 % X 0 mirrors ~5.5 % X 0 STABILITY: after an initial deformation ~1 mrad, stable: 0.1 mrad over ~ 3.5 y

10. 10 Silvia DALLA TORRE Playa del Carmen, 30/11-5/12/2004 - 5 th RICH Workshop Gas System for: P constant +/- 0.1 mbar P constant +/- 0.1 mbar to limit  P on - vessel windows to limit  P on - vessel windows quartz plates quartz plates He beam pipe He beam pipe gas filtering (remove H 2 O, O 2 ) gas filtering (remove H 2 O, O 2 ) filling with / recovering C 4 F 10 filling with / recovering C 4 F 10 RICH-1 C 4 F 10 GAS SYSTEM PLC and electricalinstallation compressors filters liquidstoragetank liquifier vessel

11. 11 Silvia DALLA TORRE Playa del Carmen, 30/11-5/12/2004 - 5 th RICH Workshop PRESENT (>2002) GAS PERFORMANCES gas (atm. P) leak rate = 90 l/d extremely reduced leak rate vessel volume ~ 85 m 3 total o-rings : ~ 100 m very good transparency (better than design) -gas cleaning, see O. Ullaland’s talk -on-line filters, separate functions: -Cu catalyst, ~ 40 0 C for O 2 -5A molecular sieve, ~ 10 0 C for H 2 O transmission through 1,87 m, corresponding to: H 2 O: ~1 ppm, O 2: ~3 ppm typical wavelength (nm) transmission C 4 F 10 : N2 = 95 : 5 stabile !

12. 12 Silvia DALLA TORRE Playa del Carmen, 30/11-5/12/2004 - 5 th RICH Workshop PREDICTING ON-LINE (n-1) [(n-1) meas – (n-1) cal ] / (n-1) (n-1) cal from measured P, T continuous line (n-1) meas from off-line data analysis red dots prediction at ‰ level to allow quasi-online data processing, a must: COMPASS data rate = 3 TB/day

13. 13 Silvia DALLA TORRE Playa del Carmen, 30/11-5/12/2004 - 5 th RICH Workshop RICH-1 RAW INFORMATION an event, calibration run low intensity: 10 7 /sec an event, standard run nominal intensity: 4 x10 7 /sec

14. 14 Silvia DALLA TORRE Playa del Carmen, 30/11-5/12/2004 - 5 th RICH Workshop RICH-1 CENTRAL REGION Distance from Beam (mm) Efficiency Monitor PID efficiency fromMonteCarlo (beam halo off) 2 combinated effects: - beam halo - central dead zones - central dead zones all dead zones only photon detector dead zones photons generated by the beam halo overlap of event images

15. 15 Silvia DALLA TORRE Playa del Carmen, 30/11-5/12/2004 - 5 th RICH Workshop “SINGLE PHOTON” PERFORMANCES  hit (mrad)  ring (mrad) all particles selecting particles according to polar angle and producing  ring slices  information on: resolution resolution number of detected photons number of detected photons background background example

16. 16 Silvia DALLA TORRE Playa del Carmen, 30/11-5/12/2004 - 5 th RICH Workshop NUMBER OF PHOTONS n. of ph.s background rings with < 5 ph.s not reconstructed not reconstructed fit above 36 mrad adding up regions 3-6  particle <30 mrad 30-60 mrad 30-60 mrad 120-150 mrad 120-150 mrad 150-180 mrad 150-180 mrad 90-120 mrad 90-120 mrad 60-90 mrad 60-90 mrad

17. 17 Silvia DALLA TORRE Playa del Carmen, 30/11-5/12/2004 - 5 th RICH Workshop IS THE NUMBER OF PHOTONS UNDERSTOOD ? Very low beam intensity ~ 4  10 6 /spill threshold at 3  HV = 2000 V eff.  N ph  ~ 21 expected: 22 =6.3 =6.5 = 21.3 - 3 = 20.5 - 3 ring centres of the selected particles

18. 18 Silvia DALLA TORRE Playa del Carmen, 30/11-5/12/2004 - 5 th RICH Workshop RICH-1 RESOLUTION  measured from reconstructed rings  RING (mrad) COMPARISON OF RING RESOLUTION DIRECTLY MEASURED (reconstructed rings) AND CALCULATED FROM SINGLE PHOTON RESOLUTION: FULL DETECTOR UNDERSTANDING single photon resolution  photon (mrad) p (GeV/c) ring resolution  calculated from single photon resolution  particle (mrad) 2.5  /K sep. up to 40 GeV/c

19. 19 Silvia DALLA TORRE Playa del Carmen, 30/11-5/12/2004 - 5 th RICH Workshop PID with COMPASS RICH-1  K p  particle > 25 mrad p (GeV/c) > p thr (K) + 2 GeV/c

20. 20 Silvia DALLA TORRE Playa del Carmen, 30/11-5/12/2004 - 5 th RICH Workshop PID EFFICIENCY  ± from K s decays p> thr. (= on average 0 photons ) p> thr. + 0.5 GeV/c (=on av. 5 det. ph.s) p> thr. + 1.2 GeV/c (=on av.8 det. ph.s) p> thr. + 2 GeV/c (=in m. 10 det. ph.s) 0-30 mrad = = 12.4 GeV/c = = 9.3 GeV/c = 7.1GeV/c = 7.1GeV/c = = 5.8 GeV/c = = 4.9 GeV/c = = 4.3 GeV/c 30-60 mrad 60-90 mrad 120-150 mrad 150-180 mrad 90-120 mrad MOMENTUM SPECTRA IN  particle BINS  particle (mrad) EFFICIENCY EFFICIENCY 

21. 21 Silvia DALLA TORRE Playa del Carmen, 30/11-5/12/2004 - 5 th RICH Workshop K ± from  decay (sample purity: 84% ) p> thr. + 2. GeV/c (= on av. 5 det. ph.s) (= on av. 5 det. ph.s) EFFICIENCY, learning curve  ± da decadimenti K s (sample purity: 94% ) p> thr. + 0.5 GeV/c (= on av. 5 det. ph.s) (= on av. 5 det. ph.s) software upgrade   particle (mrad) EFFICIENCY EFFICIENCY    particle (mrad) EFFICIENCY EFFICIENCY  PD stabilit y gasquality

22. 22 Silvia DALLA TORRE Playa del Carmen, 30/11-5/12/2004 - 5 th RICH Workshop 2002 : S eff (*) = 151 (8) 2003: S eff = 674 (17) (*) S eff =S/(1+B/S) A remarkable example:  G/G open charm-signal  D 0 & D 0 without microvertex detector RICH-1 in COMPASS PHYSICS 2002  2003 (2004) S eff /day * 4.9 Preliminary

23. 23 Silvia DALLA TORRE Playa del Carmen, 30/11-5/12/2004 - 5 th RICH Workshop CONCLUSIVE REMARKS  COMPASS RICH-1 is fully operative  plateau performances since 2003  COMPASS RICH-1  designed ~ mid 90’s  challenging requirements concerning  transversal size and  rates (beam, trigger)  large size VUV gas RICH  limitations for the operation of large size CsI photocathodes coupled to gas detectors in radioactive environments have been encountered  “single photon” resolution is satisfactory (~ parameter design)  “ring resolution” limited by physical background  ring resolution allows 2.5   / K separation up to 40 GeV/c  central for COMPASS physics (demonstrated in polarized DIP)