COMPASS calorimeters S. Platchkov IRFU, CEA-Saclay GDR, 8-9 avril 2008 SP; Apr. 8, 2007 GDR Nucleon

Outlook The COMPASS calorimeters Calibration issues – T9 test beam results Monitoring – laser upgrade The DVCS project – ECAL0 calorimeter SP; Apr. 8, 2007 GDR Nucleon

COMPASS set-up SP; Apr. 8, 2007 GDR Nucleon

ECAL1 OLGA MAINZ GAMS Electronics for all: 320 blocks (143x143 mm2) SADC 291 400 SP; Apr. 8, 2007 GDR Nucleon

ECAL2 Matrix: 64 x 48 blocks with 10 x 10 central hole 2972 channels (all are Lead Glass GAMS blocks) Electronics: FIADCs SADCs SADC FIADC 183 SADC 244 SP; Apr. 8, 2007 GDR Nucleon

COMPASS LG blocks properties SP; Apr. 8, 2007 GDR Nucleon

Calibration issues SP; Apr. 8, 2007 GDR Nucleon

Calibration of ECALs (during µ runs) Energy range: ~5 GeV – 50 GeV Use SPS 40 GeV electron beam (~few 103/spill) Two-step procedure: 1. Use e- to measure ADC peak values. Change HVs accordingly 2. Use e- a second time for fine tuning. Use the resulting correction factors for energy measurements. ECAL1 Energy range: ~1 GeV – 10 GeV Use halo muons (no e- beam of low enough energy) Refine the procedure at the CERN-T9 test beam facility SP; Apr. 8, 2007 GDR Nucleon

T9 test beam set-up (CERN, October 2007) Energy: 1 – 15 GeV Beam: p, µ, e- Scintillator counters Scintillator hodoscope RichWall prototype HCAL2 3x3 modules Cherenkov counters ECAL modules: Shashlik 5x5 GAMS 5x5, Mainz 3x2, Olga 2x2 SP; Apr. 8, 2007 GDR Nucleon

T9 set-up SP; Apr. 8, 2007 GDR Nucleon

Calibration procedure First step (relative, or inter-calibration) Beam centered at each cell Assume all beam energy is deposited in the same block For electrons For muons Second step (absolute calibration) Sum of 9 or 25 blocks (all the deposited energy): Rescale: SP; Apr. 8, 2007 GDR Nucleon

SADC spectra after muon intercalibration SP; Apr. 8, 2007 GDR Nucleon

Calibration using muon “MIP” energy Mean = 5.628 +/- 0.003  MIP energy: 0.7 GeV SP; Apr. 8, 2007 GDR Nucleon

Final calibration using e- beam energy MPV = 0.620 +/- 0.004 MIP energy: ~10% underestimated or wrong assumption? SP; Apr. 8, 2007 GDR Nucleon

Muon “energy losses” in PbO modules How large is the muon “MIP” loss in PbO ? Measured: Eµ = 620 MeV Calc: Calculated: Eµ = 280 MeV !!  620/280 ≈ 2.2 !! But also: differences as a function of the energy: Differences between -10 and +1% ! SP; Apr. 8, 2007 GDR Nucleon

Muon “energy losses”: Cherenkov photons from muons: from 1) Ionization, 2) Cherenkov radiation Ionization loss Eion : energy dependence in PbO Eion( 1 GeV) = 1.40 g-1cm2 x 45 cm x 3.86 g.cm-3 = 243 MeV Eion( 4 GeV) = 1.63 g-1cm2 x 45 cm x 3.86 g.cm-3 = 283 MeV Eion(10 GeV) = 1.81 g-1cm2 x 45 cm x 3.86 g.cm-3 = 314 MeV Difference = 71 MeV (~11% of 620 MeV between 1 and 10 GeV) Cherenkov “loss” : ECh Proportional to 1/β2; For 1 GeV: β = 0.995 For 2 GeV: β = 0.998  Nearly constant as a function of the energy SP; Apr. 8, 2007 GDR Nucleon

Estimate the number of photons Very crude estimation…(uncertainties…) Muon ionization loss (4 GeV) Efficiency (0.3-0.7 µm): ~10% Detected by PM: ~1300 g/GeV For 283 MeV: ~370 photons Muon Cherenkov “loss” Number of Cherenkov g’s (0.3-0.7µm): ~200/cm;  9000 for 45 cm Efficiency: ~10% Detected by PM: ~900 photons 900/370 ≈ 2.4 Autiero et al., NIM A387 ( 1997) 352 More precise estimation needed: Monte Carlo being developed (Mainz U.) SP; Apr. 8, 2007 GDR Nucleon

GAMS: e and µ peaks, 5 GeV GAMS: Cherenkov calorimeter ~625 MeV SP; Apr. 8, 2007 GDR Nucleon

Shashlik: e and µ peaks, 4 GeV Shashlik: Pb/scintillator sampling calorimeter ~280 MeV SP; Apr. 8, 2007 GDR Nucleon

Shashlik calorimeter Homogeneous calorimeters: Sampling calorimeters Ex: PbO, BGO, PbWO4, NaI, PbF2, … Light is generated in the detector volume PbO is radiation NOT tolerant Sampling calorimeters Ex: Pb/Scint, U/Ar U/Scint, etc… Absorber and detector materials are separated Radiation resistant Delicate to calibrate COMPASS decision 2008 hadron beam: replace the central part of ECAL2 with Shashlik (800 blocks) of Pb/scintillator SP; Apr. 8, 2007 GDR Nucleon

Shashlik module Pb/scintillator sampling calorimeter 155 layers, 370x40x40 mm3 SP; Apr. 8, 2007 GDR Nucleon

GAMS calibration: 1 and 6 GeV From: G. Khaustov SP; Apr. 8, 2007 GDR Nucleon

GAMS: linearity and resolution (preliminary) Analysis: G. Khaustov SP; Apr. 8, 2007 GDR Nucleon

Shashlik: linearity and resolution (preliminary) Analysis: G. Khaustov SP; Apr. 8, 2007 GDR Nucleon

keeping the calibration constant Monitoring or, keeping the calibration constant SP; Apr. 8, 2007 GDR Nucleon

ECAL2: calibration values SP; Apr. 8, 2007 GDR Nucleon

ECAL1: LED amplitudes Variations not well understood SP; Apr. 8, 2007 GDR Nucleon

Laser monitoring, based on CMS design Before the run: Systematic hardware check Measurement of the linearity block by block Relative inter-calibration of all modules During the run: Performs individual channel hardware check online (LG transparency, HV, PM, electronics, SADC,… = all OK? ) Monitors short term and long term variations Detects system self-failures PbO cell SP; Apr. 8, 2007 GDR Nucleon

Light distribution SP; Apr. 8, 2007 GDR Nucleon

Test fiber bundle SP; Apr. 8, 2007 GDR Nucleon

Fiber optical transmission – expected results Optical transmission test bench Relative transmission for 2151 fibers SP; Apr. 8, 2007 GDR Nucleon

DVCS - the ECAL0 calorimeter SP; Apr. 8, 2007 GDR Nucleon

Additional equipment to the COMPASS setup μ’ DVCS: μ p  μ’ p’   ECal1 + ECal2   10° 2.5m liquid H2 target to be designed and built + additional calorimeter ECal0 at larger angle (° background) L = 1.3 1032 cm-2 s-1 4m long Recoil Detector to insure exclusivity to be designed and built Nμ=2.108/SPS cycle (duration 4.8s, each 16.8s) μ p’ SP; Apr. 8, 2007 GDR Nucleon

Calorimeter acceptances (Simulation DVCS) xbj Q2 Existing Calorimeters Xbj-bins + 4m x 4m ECAL0 SP; Apr. 8, 2007 GDR Nucleon

Photons in ECALs (Simulation from A.Sandasz) <θγ> = 200 mrad <θγ> = 72 mrad <θγ> = 18 mrad θγ [rad.] θγ [rad.] θγ [rad.] <Eγ> = 7.6 GeV <Eγ> = 19 GeV <Eγ> = 54 GeV Eγ [GeV] Eγ [GeV] Eγ [GeV] SP; Apr. 8, 2007 GDR Nucleon

ECAL0 Dubna prototype - design Lead/Scintillator type 200 mm long, 73x73 mm2 4mm Scint 4mm Pb First tests at COMPASS end 2007 R/O: AMPDs SP; Apr. 8, 2007 GDR Nucleon

Merci! SP; Apr. 8, 2007 GDR Nucleon