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

4. RICH Process Rates signal (e,e’K) 10-4 – 10-2 accidentals (e,e’)(e,pi)
(e,e’)(e,k)
100
0.1
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

5. n fixed by the momentum(2GeV/c)
Cos q =1/nb Db/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 ( 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. 3 PD

12. Probably underestimated
2200 V
Jlab Cosmic tests June 03
G~ 2.5 x 105
A0=26
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. detector ready end ofJuly
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 (very difficult to estimate with cosmic, conservative)
Fixing freon leakage ==> 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 coulomb/mm2/s