1. Il Ring Imaging CHerenkov (RICH) detector a Jefferson Lab – Hall A

2. Kaon Identification through Aerogels The PID Challenge Very forward angle ---> high background of p and p -TOF and 2 aerogel in not sufficient for unambiguous K identification ! AERO1 n=1.015 AERO2 n=1.055 p k p p h = 1.7 : 2.5 GeV/c Protons = A1A2 Pions = A1A2 Kaons = A1A2 p k All events p k

3. K AON Id Requirements physics case ProcessRates signalBound states (e,e’K) 10 -4 – 10- 2 accidentals (e,e’)(e,  ) (e,e’)(e,p) (e,e’)(e,k) 100 0.1 Forward angles  higher background of p and p  TOF and 2 Threshold Cherenkov NOT sufficient for unambiguous kaon identification  RICH DETECTOR Signal Vs. Background

5. RICH detector –C 6 F 14 /CsI proximity focusing RICH “ MIP ” Performances - N p.e. # of detected photons(p.e.) - and   (angular resolution) Cherenkov angle resolution Separation Power N. of detected photoelectrons maximize minimizee

8. The R ICH detector at Jefferson Lab

9. RICH photocathode installation

11. J LAB Hall A RICH flying to hunt kaons into the detector hut

13. UV source and optical system The evaporator system Quantum Efficiency measurement system

15. Good uniformity (±10%)and reproducibility Bad spot QE measurements cern latest results x-coordinate across GEM Relative QE (%) 40 0

16. R ich Performances ‘key parameters’: Angular resolution: N pe p /p ratio: N pe for  and p Cherenkov angle for p Cherenkov average angle (rad) Nclusters

17. RICH – PID – Effect of ‘Kaon selection p P K Coincidence Time selecting kaons on Aerogels and on RICH AERO KAERO K && RICH K Pion rejection factor ~ 1000

19. Dilepton pair Beam Pipe HBD Gas Volume: Filled with CF 4 Radiator (n CF4 =1.000620, L RAD =50 cm) Cherenkov light forms “blobs” on an image plane (r BLOB ~3.36cm) Triple GEM detectors (12 panels per side) Space allocated for services Windowless Cherenkov Detector Radiator gas = Avalanche Gas Electrons radiate, but hadrons with P < 4 GeV/c do not Pcb pad readout (~ 2x2 cm 2 ) 5 cm 55 cm e-e- e+e+ q Pair Opening Angle The HBD Detector CsI photocathode covering GEMs

20. The Clean Tent at USB Entrance Foyer Level of Clean Room evaporator glove box GEM storage vessel laminar flow hood

21. The Evaporator Evaporation Chamber Quantum Efficiency Station Magnetically coupled driver for moving the GEMs inside the vacuum. on loan from INFN Roma