A RICH detector for CLAS 12 Physics motivations

A RICH detector for CLAS 12 Physics motivations Status of the project Future Plans Patrizia Rossi for the RICH Collaboration Laboratori Nazionali di Frascati- INFN (Italy) CLAS 12 2 nd European Workshop - March 7 -11, 2011 - Paris, France

CLAS 12 Physics Program Study of the internal nucleon dynamics: TMD distribution and fragmentation functions & GPDs Hadron PID to achieve flavor tagging Quark hadronization in the nuclear medium Hadron PID to strongly constrain the models Spectroscopy Hadron PID to access rare processes This program requires good identification of and K over the full kinematical range accessible with CLAS 12 Particle identification is an essential part of any experiment, and has contributed substantially to our present understanding o elementary particles and their interaction

The power of a good PID LHCb (MC prediction) NO RICH With RICH Need to distinguish Bd from other similar topology 2 -body decays and to distinguish B from anti-B using K tag.

CLAS 12 PID Ge. V/c 1 /K H RIC CH RI /p 2 TOF TOF e/ HTCC 4 5 6 LTCC RICH 7 8 full pion / kaon / proton separation over whole accessible momentum range of 2 – 8 Ge. V for SIDIS exp. 9 10 HTCC LTCC RICH EC/PCAL H RI C K/p 3 SIDIS kinematics /K separation of 4 -5 @ 8 Ge. V/c for a rejection factor ~1000

Concept of a RICH for CLAS 12 Projective geometry: 6 radial sectors ~ 3 m radius 25 o ll cm a F w 3 S RU TO m c 124 538 B ~ 40 G FTO 1. 2 m gap DC

RICH for CLAS 12 2 mrad C RI H RIC RADIATOR 8 mrad Freon+UV-light detection does not provide enough discrimination power in the 28 Ge. V/c momentum range Aerogel mandatory to separate hadrons in the 2 -8 Ge. V/c momentum range collection of visible Cherenkov light use of PMTs

RICH for CLAS 12 Challenging project: § Large Detector area (several m ) 2 RI C C RI RI C § Operation in magnetic field & with high intensity e- beam Innovative new technologies § Radiator Material § Photo-detectors § Electronics ~ 6 m 2 entrance window From a proximity focusing to an “hybrid” RICH 1 m depth

RICH for CLAS 12: status and plans MC Simulation for basic parameters studies ✔ (stand-alone GEANT-3 based code) - Aerogel refractive index and thickness - Photon detector pixel size - Gap dimension C K C Fix the pixel size of PMTs < 1 cm 5 8 5 8

RICH for CLAS 12: status and plans MC Simulation for basic parameters studies ✔ (stand-alone GEANT-3 based code) - Aerogel refractive index and thickness - Photon detector pixel size - Gap dimension Validation of simulations and check performances: RICH prototype construction - Procurements of parts done ✔ - Tests of the radiators and the photo-detectors at Frascati – setup installation started - Prototype beam tests MC Simulation with RICH geometry included into the CLAS 12 GEMC package (Geant 4/C++ based code) - focussing mirrors option studies in progress - Development of the reconstruction tracking algorithm of charged particles in progress Front-end & Readout Electonics - Available readout system to be customized for CLAS 12 - Test of the modified system in CLAS 12 conditions hile) C ( M UTFS - Production of the needed boards y b d itte m m - Quality checks/characterization o C Preparation of a Conceptual Design Report by this summer

Transparent Silica Aerogel with High n Makoto Tabata, Ichiro Adachi et al. for Belle II aerogel RICH group New production technique invented for high refractive index greater than 1. 05 –Optical quality degraded if sample with n>1. 05 is produced in a conventional method –“Pinhole drying (PD)” method artificially shrinks alcogel to obtain high index –Transparency doubled for n>1. 05 aerogel with this new method Some new developments also in Novosibirsk First use of high refractive index aerogel (n=1. 13) in particle physics experiment [A. Yu. Barnyakov et. al. , Nucl. Instr. and Meth. A 598 (2009) 163]

GEMC Simulations GEANT 4 toolkit: Toward a complete simulation: realistic geometry / detailed optic effects track multiplicity / background full Cherenkov ring simulation chain Ongoing activities: Improve simulation Reduce costs mirrors

The focusing Mirror System Low material budget Direct & reflected photons Goals: • instrument only forward region • reduce active area (~1 m 2/sect) • minimize interference with TOF system • allow larger aerogel thickness (focalization)

The focusing Mirror System Minimize TOF detector area (~1 m 2/sector) interference with FTOF Reflecting inside • spherical (elliptical) mirror within gap volume for backward refl. • plane mirror just beyond radiator forward reflections Low material budget direct & reflected Preliminary studies with mirrors (to reduce instrumented area): - focalization capabilities shown - ring patterns for positive and negative mesons at different angles and momenta reconstructed Different scenarios (refractive index, radiator thickness, mirror geometry) are being explored

The reconstruction algorithm: Direct Ray Tracing (DRT) For each track, t, and particle hypothesis, h, use direct ray tracing for a large number of generated photons to determine the hit probability for each PMT The measured hit pattern is compared to the hit probability densities for the different hypotheses by a likelihood function. is the hit pattern from data = 1 if the ith PMT is hit = 0 if the ith PMT is not hit is the probability of a hit given the kinematics of track t and hypothesis h E F / N F N +I is the probability of no hit is the total number of expected PMT hits is a background term Hypothesis that maximizes L N A is assumed to be true

200 trials per event Aerogel: - n=1. 06 - thickness increasing with radius: Direct ring example M. Contalbrigo INFN/FE Hit prob > 3 10 -3 2 cm up to 13 deg 4 cm 13 -15 deg 6 cm 15 -17 deg 8 cm 17 -20 deg 10 cm > 20 deg Mirror: 14 o-25 o PMTs: UBA PPMT (i)

Average Np. e. + - 5° Np. e. > 5 for reflected rings Np. e. > 12 for direct rings

LH -LHK, p + - Contamination as expected from the GEANT 3 simulation! Very promising results also for the reflected events 5°

Average Np. e. + - Mirror 14°-25° Mirror up to 35 o: Viable configuration

LHp-LH K, p - Mirror 14 o-25 o n=1. 06 Aer. thick 2 -4 -6 -8 -10 cm + - n=1. 03 Aer. thick 3 -6 -9 -12 -15 cm + - n=1. 03 in principle good due to the larger Cherenkov angle separation

Average Np. e. + - n=1. 06 better for patter recognition in the presence of backgrouns n=1. 06 Jo

Average Np. e. + - Jo

Photo-detectors REQUESTS: visible light compact single photon Small pad size § Multi-anode PMTs § Si. PM MA-PMT Dimentional outline (mm 3) Effective area (mm 2) Pixel size (mm 2) Comment R 7600 26 x 28 18 x 18 4. 5 x 4. 5 (4 x 4) Optimized for single photon Recommended by Hamam Low packing factor H 8500 -C 52 x 28 49 x 49 5. 8 x 5. 8 (8 x 8) Excellent packing factor Not optimized for single photon Not recommended by H. H 8500 -C-03 R 8900 -00 -M 16 UV glass window 25 x 28 20 x 20 4. 8 x 4. 8 (4 x 4) R 8900 -100 -M 16 R 11265 Optimized for single photon High packing factor Sensitive to B Super bialkali 23 x 23 2. 8 x 2. 8 (8 x 8) Optimized for single photon High packing factor Insensitive to B Available only 8 x 8 - Preliminary tests results with H 8500 and R 7600 at Glasgow U. - R 8900 will be tested soon

Front-end & Readout Electronics Front-end & readout board developed by INFN-Genova group (frontend chip MAROC from IN 2 P 3 -Orsay) A. G. Argentieri et al. NIM A 617 (2010) 348– 350 • Independent channels (unique!) with selectable gain for non-uniformity compensation • Smart (reconfigurable) selftriggering by active FPGA (trigger topology scheme) • Up to 4096 channels in compact form factor • Fast Readout • Compact (high density of the front end)

Players in the Game INSTITUTIONS Researchers ARGONNE NL 3 INFN 13 Bari, Ferrara, Genova, Frascati, Roma/ISS GLASGOW U. JLAB U. CONN UTFSM (Chile) 2 2 3 3 NEW COLLABORATORS, CONTRIBUTIONS ($, €. . ), MANPOWER, ARE VERY WELCOME TO JOIN THIS EXCTING PROJECT

Conclusions Good hadron identification is required for studies of the internal nucleon dynamics RICH technique is the clear choice when hadron identification is required at high momenta Preliminary studies show that aerogel plus visible light detection with MA-PMT can match the requirements for a RICH for CLAS 12. Work is in progress to: - Improve simulation and reconstruction algorithm - Define a CDR by this summer - validate simulations and check performances by testing components and building a prototype Initial R&D funding available from INFN and ANL