A RICH Detector for strangeness physics A RICH Detector for strangeness physics in Hall A at Jefferson Lab in Hall A at Jefferson Lab. Why. How. Main Characteristics/Expected performances.. Tests. CERN. Cosmics. Beam. Conclusions and outlook IMAGING 2003 – Stockholm – 24 th – 27 th June 2003 F. Cusanno – Hall A RICH collaboration

 -N Interaction V  N = V ( r ) + V  ( r ) S .S N + V  (r ) S N.l N  + V T ( r) S 12 Very important for astrophysics (neutron star formation) E F. Garibaldi, S. Frullani, J. LeRose, P. Markowitz, T. Saito

ProcessRate signal(e,e’K)10 -4 – accidentals(e,e’)(e,pi) (e,e’)(e,p) (e,e’)(e,k ) RICH Project started Summer 98 Test CERN November 00

 =  msr  p/p = 5%  p/p =1 x 10 -4

Cos  =1/n   /  = tg  With N p.e. per ring    /  N - n fixed by the momentum(2GeV/c) C 6 F 14, transparent down to 160 nm - compact (~ 50 cm) x 1820 mm2 - relatively thin (18% X0) - quarz window 5 mm 15 mm 300 nm

MCarlo

radiator NEOCERAM Quartz cylinders, 5mm quartz window

KHz

Freon System

The fluid is degassed by bubbling high purity nitrogen through a bed of 2 micron pore, sintered stainless steel cylinders and then through the liquid to scavenge air in solution in the fluid. The sintered stainless cylinders maximize the contact area between the nitrogen and the radiator liquid. This significantly speeds the degassing of the radiator liquid. The nitrogen then passes through a cold condenser that removes the perfluorohexane from the air/nitrogen/perfluorhexane stream and returns the perfluorhexane to the tank. The fluid also passes over an alternating pair of molecular sieve filters before being pumped to the radiator. Several methods are used to verify the quality of the radiator fluid. The effluent from the degassing tank passes through an oxygen and moisture sensor. An on-line transmission monitor measures the transmission of the liquid in the return flow from the radiator. Periodically the return flow is temporally diverted through an optical sample cell. The light from a mercury vapor light, filtered to select the appropriate wavelength (184 nanometers) is passed through a beam splitter. One light beam goes through the sample cell and its intensity measured with photodiode. The other light beam goes directly to another photodiode and is used as a reference. The ratio of outputs from the two photodiodes is an approximate measure of radiator liquid transmission at the selected wavelength.

Bandpass filter

gas system

CERN tests Nov ‘00

CERN tests 11/00 7 GeV/C  beam Argon CH 4 (25/75) 2 photocathodes (Rome and CERN) Equal performances N = ~ 12

Jlab Cosmic tests Aug V

On beam tests March 02

2150 V2250 V G~ 5 x 10 4 G~ 1 x 10 5

MPWC Gain Comparison STAR PRESENT STATUS OLD STATUS HV (V)ALICEOUR RICH MIP signal size (# of pads) ‘Good working’ range

Jlab Cosmic tests June 03 Scan in positioning: presently we are on the left side, 160 mm distance from boundary (and  >0). Extrapolating to  =0 in with the whole ring in the active area: ~ p.e. (as at CERN) 2150 V G~ 2.5 x 10 5 A0=26

Conclusions The present Hall A PID setup is not sufficient for unambiguous K identification needed for hypernuclear spectroscopy A Proximity focusing C 6 F 14 /CsI RICH detector has been built and tested Performances in the expectations - gain problem understood and fixed CsI evaporation technique unders control Detector ready to be installed for the Hypernuclear experiment