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Mauro Iodice INFN Roma (Italy)

RICH detector update. Mauro Iodice INFN Roma (Italy). Hall A Collaboration Meeting - JLAB May 18, 2004. Cherenkov angle resolution. Separation power. Particle Particle mass m 2 mass m 1. R ing I maging CH erenkov Fundamentals. “ MIP ”.

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Mauro Iodice INFN Roma (Italy)

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  1. RICH detector update Mauro Iodice INFN Roma (Italy) Hall A Collaboration Meeting - JLAB May 18, 2004

  2. Cherenkov angle resolution Separation power Particle Particle mass m2 mass m1 Ring Imaging CHerenkov Fundamentals “MIP” Relevant quantities:NP.E. N. of detected photons AND sqangular uncertainty N. of detectedphotoelectrons : eQE = single photoelectron detection efficiency Q = photoconverter Quantum Efficiency T = transmission of radiator, gas and windows Minimize Maximize Mauro Iodice - Hall A Collaboration Meeting - JLAB May 18, 2004

  3. JLAB Hall A RICH layout – similar to ALICE HMPID RICH Freon Radiator: 1800x400x15 mm3 single box with quartz windows glued on neoceram housing Grid plane: 100 mm positive wires (collects electrons ionized in the gap) Wire chamber : composed by 20 mm anode wires plane sandwitched between a cathode plane formed by 100 mm wires and the cathode plane formed by the photocathodes Three Photocathodes : 403x640 mm2each, divided in 8.4 x 8 mm2 size pads evaporated with a 300 nmCsI layer Mauro Iodice - Hall A Collaboration Meeting - JLAB May 18, 2004

  4. JLAB Hall A RICH: some components Mauro Iodice - Hall A Collaboration Meeting - JLAB May 18, 2004

  5. JLAB Hall A RICH flying to hunt kaons into the detector hut Mauro Iodice - Hall A Collaboration Meeting - JLAB May 18, 2004

  6. JLAB Hall A RICH Event Display Mauro Iodice - Hall A Collaboration Meeting - JLAB May 18, 2004

  7. JLAB Hall A RICH OPERATING conditions • Gas: Pure Methane (Minimize Photon Feedback, High Q.E.) • High Voltage: ~ 2100 Volts for a gain of 8x104 • Grid Voltage: 250 - 450 Volts • Optimal trigger to read-out delay: ~400 ns (peaking time of gassiplex response) cluster charge and hit size MIP charge and hit size Mauro Iodice - Hall A Collaboration Meeting - JLAB May 18, 2004

  8. Rich Performances – key parameters : p Cherenkov angle reconstruction Npe for p and P Nclusters Cherenkov average angle (rad) Npep/p ratio : Angular resolution : Mauro Iodice - Hall A Collaboration Meeting - JLAB May 18, 2004

  9. Rich Performances – PID : p/K population ratio Aero Selected p Angular resolution Aero Selected K (!) Aero Selected P Separation power Aero Selected K on a large sample of filtered data This would accept ~ 10-4 pions x p/K ratio 1/100 pion contamination …. But NON GAUSSIAN TAILS GIVE AN IMPORTANT CONTRIBUTION ! Kaon selection: Mauro Iodice - Hall A Collaboration Meeting - JLAB May 18, 2004

  10. Rich – PID Strategy: • Particle Identification is also based on the following (correlated) quantities : • Single photon 2 distripution (Prob(2 ,ndof)) • log-likelihood function L • For all measured tracks different particle hypothesis (p,K,P) are made, and the corresponding central Cherenkov angles are computed (Qp/K/P) Lp/K/P = n Weighted number of reconstructed hits Mauro Iodice - Hall A Collaboration Meeting - JLAB May 18, 2004

  11. Rich – PID – Kaon selection results : Time of coincidence for Aerogel Selected Kaons w/o and w/ rich : AERO K AERO K && RICH K p P K Mauro Iodice - Hall A Collaboration Meeting - JLAB May 18, 2004

  12. Rich – PID – Pion rejection factor : Time of coincidence for Aerogel Selected Pions: effect of Rich Kaon selection AERO p && RICH K AERO p p p N.Evts in the peak Backgnd subtr. = 64656 N.Evts in the peak Backgnd subtr. = 63 Pion rejection ~ 1000 Mauro Iodice - Hall A Collaboration Meeting - JLAB May 18, 2004

  13. Rich Possible improvements : • MWPC stability for high rates • For single rates ≤ 60 KHz HV=2100 V is OK • In the range 60 KHz – 100 KHz HV=2075 V is OK • Above 100 KHz HV must be reduced further •  MWPC stability (and mechanics) needs to be studied • for high rates running (work is needed!) • However running at reduced gain with moderately good • performance seems to be feasable (see next slide) • p/K separation for p>2.5 GeV/c • Doable “just” replacing the radiator. • DAQ rate bottleneck (~1KHz) can be overcome replacing front-end Mauro Iodice - Hall A Collaboration Meeting - JLAB May 18, 2004

  14. Rich MWPC performance at lower HV HV = 2100 V HV = 1900 V Mauro Iodice - Hall A Collaboration Meeting - JLAB May 18, 2004

  15. Rich p/K separation for p > 2.5 GeV/c Radiator C5F12 n=1.24 sCh~ 5mr Radiator C6F14 n=1.29 sCh~ 5mr 4 s separation at ~ 2.5 GeV/c 4 s separation at ~ 3.0 GeV/c Mauro Iodice - Hall A Collaboration Meeting - JLAB May 18, 2004

  16. Conclusions : • The RICH detector has been successfully operated during the • hypernuclear experiment • It is a powerful tool for Particle Identification • Average Cherenkov angle resolution sq~ 5 mr in good agreement with • simulations • Clean kaon identification is possible with a pion rejection ratio ~1000 • Present analysis is still prelminary Mauro Iodice - Hall A Collaboration Meeting - JLAB May 18, 2004

  17. JLAB Hall A RICH flying into the detector hut Mauro Iodice - Hall A Collaboration Meeting - JLAB May 18, 2004

  18. JLAB Hall A RICH Event Display – altri eventi Mauro Iodice - Hall A Collaboration Meeting - JLAB May 18, 2004

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