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CLAS12 Particle Identification

CLAS12 Particle Identification. S. Stepanyan (JLAB) Probing Strangeness in Hard Processes INFN Frascati, October 18 – 21, 2010. Outline. CLAS12: physics and instrumentation PID in forward detector (baseline design) e/ p separation neutral particle identification

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CLAS12 Particle Identification

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  1. CLAS12 Particle Identification S. Stepanyan (JLAB) Probing Strangeness in Hard Processes INFN Frascati, October 18 – 21, 2010

  2. Outline • CLAS12: physics and instrumentation • PID in forward detector (baseline design) • e/p separation • neutral particle identification • charge hadron identification • Charge hadron identification in central detector (baseline design) • Improvements to the baseline design • K/p separation in forward detector • neutron detection in central detector • low energy recoil detector • CLAS12 trigger • Summary S. Stepanyan PSHP, INFN Frascati, October 18-21, 2010

  3. CLAS12 physics program • 3D Structure of the Nucleon - the new Frontier in Hadron Physics • Nucleon GPDs and TMDs – exclusive and semi-inclusive processes with high precision • Precision measurements of structure functions and forward parton distributions at high xB • Elastic & Transition Form Factors at high momentum transfer • Hadronization and Color Transparency • Hadron Spectroscopy – heavy baryons, hybrid mesons, … Already approved experiments correspond to about 5 years of running S. Stepanyan PSHP, INFN Frascati, October 18-21, 2010

  4. CLAS12 –Design Parameters Forward Central Detector Detector Angular range Tracks 50 – 400 350 – 1250 Photons 20 – 400 --- Resolution dp/p (%) < 1 @ 5 GeV/c < 5 @ 1.5 GeV/c dq (mr) < 1 < 10 - 20 Df (mr) < 3 < 5 Photon detection Energy (MeV) >150 --- dq (mr) 4 @ 1 GeV --- Neutron detection Neff < 0.7 (EC+PCAL) n.a. Particle ID e/p Full range --- p/p< 5 GeV/c < 1.25 GeV/c p/K < 2.6 GeV/c < 0.65 GeV/c K/p < 4 GeV/c < 1.0 GeV/c p(h)ggg Full range --- Forward Detector Central Detector S. Stepanyan PSHP, INFN Frascati, October 18-21, 2010

  5. High Threshold Cherenkov Counter (HTCC) for e/p separation, Low Threshold Cherenkov Counter (LTCC) for e/p separation, Scintillator counters (fTOF) @ ~650cm from the target, time resolution of 80ps Scintillator counters (cTOF) @ 50 cm from the target, time resolution of 60ps Electromagnetic calorimeters (PCAL&EC), 54 layers of lead and scintillators, 22 r.l. Detectors used for PID CLAS12, Sector mid-plane S. Stepanyan PSHP, INFN Frascati, October 18-21, 2010

  6. LTCC & HTCC Working gas C4F10 at 1 atm. Pion threshold P=2.7 GeV/c Working gas CO2 at 1 atm. Pion threshold P=4.9 GeV/c Ellipsoidal mirror system 48 5’’ quartz window PMTs S. Stepanyan PSHP, INFN Frascati, October 18-21, 2010

  7. U - plane V - plane W - plane ECal (EC&PCAL) Lead-scintillator sandwich with three stereo readout planes (UVW). Total of 22 r.l. thick, 54 layers (EC+PCAL) with longitudinal segmented 15+15+24 Transverse segmentation 4.5 cm in the first 15 layers and ~10cm in the last 39 layers. Light collection form one end of 5 to 420 cm long scintillator strips EC light readout with clear optical fibers connected to one end of scintillaotr strips PCAL light readout with wavelength shifting fibers embedded in the scintillaotr strips LG Inner PMT Inner bundle Outer PMT Outer bundle S. Stepanyan PSHP, INFN Frascati, October 18-21, 2010

  8. e/pseparation • LTCCxHTCCxEC for P < 2.7 GeV/c • HTCCxEC (will be used in the trigger) for P < 4.9 GeV/c • EC for P > 4.9 GeV/c (p/e rejection better than few %) HTCC 3p.e. HTCC 3p.e. and EC+PCAL > 0.4 GeV S. Stepanyan PSHP, INFN Frascati, October 18-21, 2010

  9. Electron detection with EC/PCAL Added pre-shower calorimeter with 15 lead-scintillator layers will allow to retain good energy resolution for up to 11 GeV/c ECAL for e/p separation for P > 4.9 GeV/c: cuts on the energy detected in PCAL and Inner part of EC, a cut on the total energy in ECAL 0.02 0.04 0.06 Pion detection efficiency Electron detection efficiency 0.08 EC only 0.1 EC+PCAL 0.12 0.14 Cut on total energy in ECAL (GeV) S. Stepanyan PSHP, INFN Frascati, October 18-21, 2010

  10. Neutron, g, and p0detection in PCAL+EC Two cluster reconstruction from high energy p0ggg decays Neutron detection efficiency 4.5 cm transverse segmentation For neutron identification and momentum measurements, time-of-flight from the target to EC planes will be used. With time resolution of ~0.3 – 0.4 ns neutrons with P<3 GeV/c can be identified 10 cm transverse segmentation Neutron momentum (GeV/c) S. Stepanyan PSHP, INFN Frascati, October 18-21, 2010

  11. Forward TOF system CLAS/e2 – 12C run Existing TOF, Panel 1a and 2a, time resolution st=150ps-180ps 58 counters in each sector, 6x6 cm2 scintillator bars with lengths from 32 to 375 cm New TOF plane, Panel 1b, time resolution st=80ps S. Stepanyan PSHP, INFN Frascati, October 18-21, 2010

  12. Charged hadron ID with fTOF • Forward TOF at L~650 cm with st~80ps will allow clean (4-5s) separation for • p/K with P< 2.6 GeV/c • K/p with P<4 GeV • p/p with P<5 GeV/c Dt – time-of-flight difference between different particles In some limited cases, where exclusivity of the reaction can be used to aid kaon ID, LTCC can be used to veto charged pions with P>2.7 GeV/c. There is a gap in p/K separation in forward detector for momenta above ~2.5 GeV/c. S. Stepanyan PSHP, INFN Frascati, October 18-21, 2010

  13. Charged hadron ID in central detector Momentum measurements in the solenoid field using silicon tracker and time-of-flight measurements with 60 ps time resolution in central TOF counters will provide p/K and K/p separation for momenta up to 0.7 GeV/c and 1.2 GeV/c, respectively. Should be sufficient for the main physics program. 5T SC Solenoid Magnet p-K 3s, s=0.06 ns K-p Silicon Tracker Scintillator Counters, dt=60ps S. Stepanyan PSHP, INFN Frascati, October 18-21, 2010

  14. CLAS12 Large acceptance detector with excellent vertex reconstruction and good PID, capable of running with high energy electron beams on variety of targets - cryogenic, gausses, solid, polarized - at luminosity of ~1035 cm-2 s-1 Suitable for exclusive reactions with multi-particle final states There is always room for improvement! Electromagnetic calorimeters CLAS12 Solenoid Low Threshold Cherenkov Counters (LTCC) Si-tracker Forward TOF Counters Drift Chambers High Threshold Cherenkov Counter (HTCC) Forward TOF Counters CLAS12 Torus S. Stepanyan PSHP, INFN Frascati, October 18-21, 2010

  15. Charge kaons in FD p detection in LTCC K/p separation > 4 - 5 GeV/c should not be a problem, production of energetic nucleons is highly suppressed - p detection in LTCC p/p fTOF K/p p/K The biggest problem is charged kaon identification above ~2.5 GeV/c. Cherenkov counters will not help, small inefficiencies for pions will cause big problems with kaon spectrum contamination. RICH with a radiator of n≈1.03 will be the ideal choice to carry over charged hadron PID above limits of CLAS12 fTOF. P, GeV/c 3 4 5 S. Stepanyan PSHP, INFN Frascati, October 18-21, 2010

  16. Neutron detection in CD Deeply exclusive reactions on neutron, e.g. DVCS on neutron - gives access to GPD E, the least known and least constrained GPD that appears in Ji’s sum rule • 80% of neutrons recoil at θlab > 40°, in momentum range 0.2 to 1.2 GeV/c • Spectator tagging method is luminosity limited (few x1033 to 1034 cm-2 sec-1) • Direct detection of neutrons in CD will fully utilize high luminosity of CLAS12 • Central neutron detector – • ~10 cm thick scintillator in the space between CTOF and solenoid inner cryostat • Neutron identification and momentum measurement using TOF • Expected momentum resolution dp/p~5%, expected efficiency ~10-15% S. Stepanyan PSHP, INFN Frascati, October 18-21, 2010

  17. Low energy recoil detector Physics motivation: • Neutron structure function – spectator tagging • Nuclear DVCS – recoil (light) nuclei tagging • Meson spectroscopy in coherent production on light nuclei Lightweight target-tracking detector system will substitute dense target and central silicon tracker in the solenoid Tracking detector RTPC based on cylindrical GEMs work well for 3 experiments with CLAS Thin wall, e.g 30mm kapton, high pressure (6-7 atm) gas targets S. Stepanyan PSHP, INFN Frascati, October 18-21, 2010

  18. Very forward electron detection (LowQ) Torus HTCC • Electroproduction at very small values of Q2 is equivalent to photoproduction using partially linearly polarized photons • Forward angle electron detector together with CLAS12 will be excellent place for baryon (e.g., S and X ) and meson spectroscopy. Part of the program can be run in parallel with electron running ECal Silicon tracker Target Detector system: tracker (can be combined with CLAS12 forward vertex tracker), calorimeter, fast scintilation detector Trigger logic with fast clustering is necessary to reject high energy showers (>7 GeV) from elastic and Moller electrons Moller absorber R1 DC S. Stepanyan PSHP, INFN Frascati, October 18-21, 2010

  19. CLAS12 trigger • CLAS12 will have free running DAQ system. ADCs and TDCs will collect data in pipeline mode. Readout of data will be performed after trigger decision is made. Expected event readout rate ~10kHz. Inclusive electron rate at 1035 cm-2 s-1 is ~3kHz. • Available fast FPGA with flash-ADCs will allow to employ a multi layer trigger system in order to find clusters in ECal, reconstruct tracks in drift chambers and identify segments in Cherenkov counters and TOF counters • Trigger decision will be made after matching clusters, hits and tracks. The goal is: • Achieve good electron selectivity using cluster energy cuts in ECal, momentum from fast tracking, and hits in HTCC (+LTCC). Singles rates will be high, it is important to suppress accidentals. [CLAS Level 1 trigger for electrons is based on the total energy cut in EC and sector based ECxLTCC coincidence and only 7% of triggered events have electron at high energy runs] • Alow additional (multi-prong) triggers from photoproduction process – • tagged quasi-real photoproduction with LowQ setup • Qusi-real photoproduction of events when electron scattered at ~0 degree [Some photoproduction reactions were successfully analyzed from CLAS high energy electroproduction data] S. Stepanyan PSHP, INFN Frascati, October 18-21, 2010

  20. Summary • In the baseline design, CLAS12 particle identification system includes gaseous threshold Cherenkov counters, scintillator counters for time-of-flight measurements, and electromagnetic calorimeters • Despite excellent design characteristics of each element, requirements of some class of experiments cannot be fulfilled with the baseline system • Important improvements to CLAS12 detector system for already proposed/approved physics program are: • neutron detection in CD • very forward electron detection • low-energy spectator/recoil detection • charged kaon identification in forward detector at momenta >2.7 GeV/c Hopefully, this workshop will bring us one big step closer to build RICH detectors for CLAS12 S. Stepanyan PSHP, INFN Frascati, October 18-21, 2010

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