RICH detector for CLAS12 … continue to explore feasibility of proximity focusing RICH in LTCC sector(s) INFN-Rome and ISS CLAS12-RICH Working Group Meeting ? 08 October 2008 08 Oct 2008 Clas12-RICH

Reminder The proximity focusing RICH consist of 3 basic components: Cherenkov Liquid Radiator Gap (gas filled space) Photon Detector 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 08 Oct 2008 Clas12-RICH

MonteCarlo Studies purpose 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 08 Oct 2008 Clas12-RICH

MonteCarlo Old GEANT3/Fortran/PAW based MonteCarlo framework used for the development of the Hall A Proximity RICH Different Geometry and Size! Limitation on photon production (due to old memory constraint), becomes relevant for radiator thickness > 2.5-3.0 cm 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) Main output parameter: skp=mean error on Cherenkov angle reconstruction of k and p 08 Oct 2008 Clas12-RICH

Working Point Assume: Two radiators (only 1 simulated); one per sector Detector span up to 2 sectors (detect photons from both radiators) Polar acceptance: from 5 to 30 degree  fix radiator size ~ 6.4 m2 Max gap length ~ 80 cm 08 Oct 2008 Clas12-RICH

MonteCarlo Result, Example 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 the are not detected) Geometry is rotated respect to the previous drawing … but represent basically the same idea. x/y are not to scale (“k Acc.Efficiency = …” is meaningless here) 08 Oct 2008 Clas12-RICH

Radiator Type ?  C5F12 Left C5F12, Right: C6F14 (points are MonteCarlo, curves are analytical functions) Left C5F12, Right: C6F14 (Geometry from the previous example) ~ 1 mr difference  C5F12 mandatory! 08 Oct 2008 Clas12-RICH

Radiator Thickness / Proximity GAP Angle reconstruction error versus Radiator Thickness, Gap length Pad/Pixel size Optimal combination: Freon Thickness ~ 3 cm GAP Length ~ 80 cm PAD size < 1 cm C5F12 single sector radiator 2sector photon detector (26 m2) Note: MC statistics is poor 08 Oct 2008 Clas12-RICH

Photon Detector Size 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 08 Oct 2008 Clas12-RICH

Photon Detector Size / Single Sector Detectors 2.04 mr Single Sector Detector +/- 30 degree, r2=417 cm 1.76 mr Detector Optimal Extension +/- 45 degree, r2=417cm 08 Oct 2008 Clas12-RICH

K-p Separation 08 Oct 2008 Clas12-RICH

Considerations The Freon C5F12 must be cooled, it evaporate at 29 C at STP !! Detector is huge! The photon detector size must probably be between 20-30 m2 (for 2 sectors) Unfortunately the Cherenkov angle resolution is not impressive; probably there is margin of improvements (both in performance and reduction of size), a careful analysis and design is required! 08 Oct 2008 Clas12-RICH