1. RICH detector for CLAS12 CLAS12 Technical Workshop P. Rossi Laboratori Nazionali di Frascati - INFN

2. Hadron PID in CLAS12 Baseline GeV/c12345678910  /K TOF LTCC HTCC  /p TOF LTCC HTCC K/p TOF LTCC  / K PID rely on LTCC performance in 3-5 GeV/c (No K/p PID in 5-8 GeV/c) RICH detector

3. r L 22  (deg) r(cm) = Ltan   38.479 K36.473 p30.358 P = 2 GeV/c L= 1m n=1.28 (liquid freon) Good separation  /K/p

4. Which RICH? Liquid Radiator (Freon) –May cover up to 5 GeV/c –Relatively inexpensive (proximity focusing RICH) Aerogel + Gas Radiators –May cover up to 10 GeV/c –Very expensive (cost Aerogel RICH ~ 5x Proximity Focusing RICH)

5. Location of the RICH Replace part of LTCC: -No impact on baseline design -Nobody will probably complain -Large space available (and to be covered!) Replace HTCC: -Impact on baseline design -Impact on tracking recontruction Simulation done for LTCC

6. LTCC sector ~ 6.2 m 2 entrance window 1 m depth

7. Proximity Focusing RICH The Proximity Focusing RICH consists of 3 basic components: Cherenkov Liquid Radiator The Radiator must be in a container (vessel) with UV transparent window (QUARTZ window) The Photon Detector must detect and localize the photon that hits on a given surface: we assume a “pads like” detector Gap (gas filled space) Photon Detector

8. A proximity Focusing RICH (~1 m 2 surface) is working in Hall A and being used in the Transversity experiment Same RICH type used by ALICE experiment ( ~10 m 2 surface) Hall A Proximity RICH

9. The Freon vessel (radiator) is the most fragile component of the detector The Freon pressure is partially compensated by the glued spacers Quarz planarity and parallelism 0.1 mm Evaporation facility CsI is evaporated on the pad panel in the evaporation chamber: 120h x 110r cm 2 (vacuum 10 -7 mbar) The evaporation facility - cost ~ 0.5 M$ has been built by the INFN Rome group (now at Stony Brook University)

10. Hall A RICH: QE measurements (July ‘08) 25 ~ 25% Quantum Efficiency has been measured

11.  K/  rejection ~ 1/1000 F. Garibaldi et al. NIM A502 (2003) Hall A RICH in Hypernuclear Exp. (2003-2005)

12. Estimate the optimal radiator thickness – Larger the thickness, higher the number of photons, higher the uncertainties on photon emission – Larger the thickness more challenging is the vessel technology (and more expensive the system) Estimate the optimal Gap length – Larger the gap, better the ‘focusing’, but larger must be the detection plane Monte Carlo studies: purpose

13.  Old GEANT3/Fortran/PAW based MonteCarlo framework the same used the for the development of the Hall A Proximity RICH but with different geometry and size!  Charged particles phase space at the LTCC-RICH entrance window assumed uniformly distributed with +/- 10 degree divergence  Use arcs as radiator and detector geometries (see next)  Limitation on photon production (~3000) old memory constraint. This becomes relevant for radiator thickness > 2.5-3.0 cm Main output parameter:  k  = mean error on Cherenkov angle reconstruction of k and  Monte Carlo studies: framework CC CKCK    K-  = (  K +   )/2

14. Working Point Assume: Two radiators (only 1 simulated); one per sector Detector span up to 2 sectors (detect photons from both radiators) Polar acceptance: 5° ÷ 30°  fix radiator size ~ 6.4 m 2 Max gap length ~ 80 cm Not to scale Unit: mm and degree

15. Black dots are charged particle positions at RICH entrance (the envelope is the radiator) Contour lines are positions at the detector level of all photons generated in the radiator The large arc is the detector surface (photons out of there are not detected) Geometry is rotated respect to the previous drawing … but represent basically the same idea Monte Carlo Result: Example x/y are not to scale

16. Points: MonteCarlo, Curves: analytical functions ~ 1 mr difference  C 5 F 12 mandatory! Geometry from the previous example Radiator Type C 5 F 12 C 6 F 14 CC CC   nn

17. Optimal combination: Freon Thickness ~ 3 cm GAP Length ~ 80 cm PAD size < 1 cm C 5 F 12 Single sector radiator 2 sectors photon detector (26 m 2 ) Angle reconstruction error vs: Radiator Thickness, Gap length Pad/Pixel size Radiator Thickness / Proximity GAP  Note: MC statistics is poor! CC CC KK KK

18. The drawings inside the plot represent different detector sizes simulated Black dots: represent the black arc at different external radius Red triangle: corresponds to the red single sector Blue square: corresponds to the blue single sector with optimal external radius Green Triangle: Optimal sector (± 45 degree) and external radius Photon Detector Size

19. 1.76 mr Detector Optimal Extension +/- 45 degree, r2=417cm Single Sector Detector +/- 30 degree, r2=417 cm 2.04 mr Photon Detector Size: Single Sector

20. K-  Separation Separation at 5 GeV/c: best case (red): 1:100 / 90% worst case (blue): 1:100 / 75%

21. HBD @ Phenix Replace MWPC with GEM Chamber  faster,  higher gain,  stability at high rate Photon Detector

22. Hall A RICHFactorClass12 RICH Readout954380 (15%) MWPC: Pads Planes2010200 (8%) MWPC: Parts (Macor Insulator)1510150 (6%) Freon (C6F14)2040800 (33%) Quartz+Neoceram3020600 (24%) Mechanical Structure3010300 (12%) Evaporation Fac.5001500 (exist) Freon Recirculation System20 (?)1.530 (?) Total210+5202420+530 Class12/Hall A Radiator:36-48 (min.-max. volume), 24 (surface) Detector:13 (surface), 4 (chs) GEM ~ 1.2 x MWPC k$ (estimation from Lire, CHF, $ and Euro) Costs - Very Preliminary!!

23. Monte Carlo simulations are in progress to study the feasibility to replace 2 sectors of LTTC with a proximity focusing RICH detector From very preliminary results it seems that:  The best choise is to use Freon C5F12 but it must be cooled! (it evaporate at 29 C at STP !!)  The detector is huge! The photon detector size must probably be between 20-30 m 2 (for 2 sectors)  The Cherenkov angle resolution is not impressive  a careful analysis and design is required to improve both the performance and the detector size Conclusions and outlook

24. Gap: 600 mm Freon Thick:20-30 mm (?)  Resolution: 1.5-1.8 mrad Channels: 70 k Proximity RICH Performance (Assume full detection acceptance)