E - 94 -107 RICH detector status report

1. E - 94 -107 RICH detector status report • - Why • How • Were we are

2. E-94-107 - High Resolution 1p shell Hypernuclear Spectroscopy F. Garibaldi, S. Frullani, J. LeRose, P. Markowitz, T. Saito forward angle&very good PID are needed to be able to get reasonable counting rates and unambiguous kaon identification in order to clean up the huge background

3. Kaon Identification through Aerogels: p p k All events p k p AERO1 n=1.015 AERO2 n=1.055 KAONS = AERO1•AERO2 Hypernuclei -> smaller scattering angle -> higher background --> something else is needed

4. RICH Contamination of pion and proton on the K signal with different PID systems, for the counting rates of two levels (10-2 Hz and 10-4 Hz) without RICH with RICH 0

5. Cosq =1/nbDb/b = tg Dq N = p.e. per ring Dq D q /sqrt(N) • n fixed by the momentum(2GeV/c) • C6 F14, transparent down to 160 nm • - compact (~ 50 cm) • relatively thin (18% X0) • 310 x 1820 mm2 • quarz window 5 mm 15 mm 300 nm

6. Many parameters affect the detector performances (# p.e.) • quartz transparency in the v.w. region of interest (160 - 220 nm) • freon purity to not absorb the emitted Cherenkov light • freon purity circuit + continuously monitoring • CsI photocathode • - evaporation + on line QE absolute measurement • QE is strongly affected by oxygen and moisture • Careful handling of photocathodes after evaporation • Continuous monitoring of gas “purity”

11. PD 3

12. 2200 V G~ 2.5 x 105 A0=26 Jlab Cosmic tests June 03 Extrapolating to q=0 and taking into account the geometric inefficiency and false triggers (cosmics): > ~ 12 p.e. (as at CERN) Probably underestimated (protons below threshold, random coincidences etc.)

13. The detector has been tested succesfully at CERN Novembre 2000(12 p.e.(14-15 with CH4))2 photocathode evaporated respectively at CERN and ROME ---> same result ! (the best CERN had obtained with the same gas mixture) • Neverthless increasing HV (2100 to 2200V) • gain back • p.e 10-12 (very difficult to estimate with cosmic, conservative) • Fixing freon leakage ==> 12-14 p.e. • (look at possible moisture contamination!) detector ready end ofJuly • spare radiator • spare f.e. electronics • 3 spare radiators to be evaporated by end of July • After trasportation, mechanical problems(a. w. to photocatode distance) • lower gain --> lower # p.e. (Difficult to measure, difficult to fix) fixed July 2002 • right gain back, but • wait for freon • Radiator accident • Fixed, but still some leak ->quench • --> lower gain (lower #p.e.) Slow control status to be checked (kaon meeting should be good (Jlab task) DAQ integration (see Bodo) Software - C++ code written by Guido being tested with CERN data for comparison with CERN (report next kaon mee. - improving the tracking (minimizing the angle error) using FPP?

14. Conclusions • Detector ready to be installed when needed • decision driven by Hall A installation schedule • (eventual “last” evaporation not to be anticipated) • only test missing: hight rate behaviour on Jlab beam • the CERN experience (the only one available) says that we should not have problem but no tests are possible with a continuous beam)(type of problem: charging up of photocathode (CsI)) • F.Piuz (Pilos proceedings): 24 hours with 6.4X10-10 Coulomb/mm2/s • - in our case (Hall A, our experiment at 250 KHz we have 2 x 10-13 coulomb/mm2/s