Electromagnetic Calorimeter for HADES at SIS100: MAMI and CERN test results Lead-glass modules Tests -  beam at MAMI energy resolution -  - /e - beam at MAMI particle separation Outlook HADES ECAL Workshop, Frankfurt a.M., October 14-15, 2010 A. Krása, F. Křížek, A. Kugler, J. Pietraszko, Y. Sobolev, J. Stanislav, P. Tlustý, T. Torrieri (NPI Řež), M. Golubeva, F. Guber, A. Ivashkin, K. Lapidus, A. Reshetin (INP Moscow), J. Pietraszko (IKF Frankfurt)

Detector modules Our proposal is to use lead glass modules from OPAL end cap calorimeter. ~ 900 modules needed, at present 1080 modules moved to GSI. Energy resolution ~ 5%/sqrt(E), E in GeV Module dimensions: 42 x 9.2 x 9.2 cm Signal Read-out PMT - EMI 9903KB (1.5'') from MIRAC (WA98 hadron calorimeter) ~720 PMT's diameter – 38 mm (1.5'') diameter of photocathode – 34 mm Front-end readout – ADC ADD-ON (Shower)+ TRB

Detector modules numberlightguide, wrapping glass wrappingPMT 1lead glass, mylarmylarEMI9903KB 2lead glass, paperpaperEMI9903KB 3NOmylarEMI9903KB 4NOpaperEMI9903KB 5NOmylarHAMAMATSU1949 EMI9903KB: 1.5” tube from MIRAC (WA98) H1949: 2.5” tube from HADES Tofino Lead glass dimensions: 9.2 x 9.2 x 42 cm

Tests – cosmic muons Source – cosmics muons: energy ≈ 2 GeV, energy deposit in module ≈ 200 MeV, Cerenkov light output corresponds to ≈577 MeV electrons count rate ≈ 20 particles / hour Measurement of pulse height (ADC) spectra – check of energy resolution various PMTs, configuration with/without lightguide July test of 5 modules before the MAMI test November test of 5 modules after the MAMI test December test of one module with PMTs (same type) with various gains, various wrappings March 2010 – now test of modules produced for one LG HADES sector

cosmics - module No.4 July 2009 Nov  = 5.4 ± 0.2 %  = 5.3 ± 0.2 %

Cosmic tests - results numberlightguide, wrapping glass wrapping PMTmean (channel) resolution (%) 1lead glass, mylar mylarEMI ± 0.3 2lead glass, paper paperEMI ± 0.5 3NOmylarEMI ± 0.4 4NOpaperEMI ± 0.2 5NOmylarH ± 0.3 Cherenkov light from cosmics muons is equivalent to 577 MeV electrons resolution 6.5% on cosmics corresponds to 5% for electrons at 1000 MeV assuming 5%/sqrt(E), E in GeV

 beam test conditions 2 days of measurement: 1)E e- = 855 MeV, I  = 25 kHz 2) E e- = 1508 MeV, I  = 5 kHz Beam: - detectors were positioned in the secondary gamma beam with continuous energy distribution from 0 to primary electron beam energy, with intensity exponentially falling with increasing energy - unless stated otherwise, the detectors were hit in the centre of their front side, and the beam proceeded along their longitudinal axis - beam diameter at detector position – 6 mm diameter Trigger: OR of signals from 8 selected scintillators in electron tagger – giving events with 8 known gamma energies in range from 0 to energy of the electron beam Purpose: to measure the module energy resolution as a function of  energy

MAMI test setup Trigger: OR of signals from 8 selected scintillators in electron tagger – giving events with 8 known gamma energies in range from 0 to energy of the electron beam Beam: detectors were positioned in the secondary gamma beam with continuous energy (intensity exponentially falling with increasing energy)

MAMI test setup Left up: test setup Left down: crew Right: detail with detectors, movable table and beam halo (looking in beam direction)

Measured  spectra ALLE= 1399MeVE= 1210MeV E= 1021MeVE= 831MeVE= 676MeV E= 261MeVE= 452MeVE= 72.1MeV E e =1508 MeV,  energy spread <= 1%, det. module No.1 ADC channel

Energy calibration E e = 1508 MeV

Resolution vs. Energy E e = 855 MeV resolution ~ k. 1/sqrt(E)

Resolution vs. Energy E e = 1508 MeV resolution ~ k. 1/sqrt(E)

Resolution vs. Energy Module No.1 resolution ~ k. 1/sqrt(E) LE: E e = 855 MeV HE: E e = 1508 MeV cosmics: cosmics muons

Resolution vs. Energy Module No.4 LE: E e = 855 MeV HE: E e = 1508 MeV cosmics: cosmics muons resolution ~ k. 1/sqrt(E)

Beam and cosmic tests - results No.lightguide wrapping glass wrapping PMTcosmics resolution (%) beam E=579MeV resolution (%) beam E=1000MeV resolution (%) 1lead glass, mylar mylarEMI6.6 ± ± lead glass, paper paperEMI8.8 ± ± NOmylarEMI7.0 ± ± NOpaperEMI5.4 ± ± NOmylarH ± ±

Resolution vs. HV E e = 1508 MeV, module No.1 resolution ~ k. 1/sqrt(E)

Resolution vs. beam position reading only module No.1 reading modules No.1+2 E e = 855 MeV, module No.1 No.1 No

CERN  - /e - beam test conditions Momentum settings: GeV/c Beam: - the T10 test beam line of the CERN PS synchrotron was used - pi- with momenta 0.4 – 6 GeV/c with admixture of electrons (increasing at lower momenta) - detectors were positioned in the pion beam - the detectors were hit in the centre of their front side, and the beam proceeded along their longitudinal axis - beam diameter at detector position – 4x4 cm defined by a trigger scintillator - triggered beam intensity: particles/ bunch, 1 bunch per 45 sec. ID: 2 m long gas Cherenkov in beam, placed 120 cm in front of lead glass, efficiency for electrons 98% Purpose: to measure the electron/pion separation as a function of momentum to measure the lead glass module time resolution, 5 identical modules tested (glass+optical grease+EMI) Trigger: OR of signals from 2 scintillators 4x4 cm

Test of lead glass - CERN May2010 Test setup on T10 CERN PS beam line Beam – pi- with momenta MeV/c with admixture of electrons

CERN test setup Right: T10 beam line Left: details with detectors

Measured e/p spectra – CERN May2010 Red – electrons green – pi- separation via gas Cherenkov ADC channel Electron peaks look worse than gamma peaks at MAMI The electron peak has long energy tail due to energy loss of electrons in air (~15m) and other detectors in T10 area.

Measured e/p spectra – CERN May2010 Same as before, but e/pi- spectra normalized to the same yield ADC channel

e  separation 2 sigma cut set on the electron peak Ratio of pions outside the cut to all pions is plotted For “RPC” the time-of-flight is used with assumed resolution of 100 ps (sigma) SHOWER

Energy resolution – CERN May2010 Looks a little worse than for gamma beam test – The electron peak has long energy tail due to energy loss of electrons in air (~15m) and other detectors in T10 area. E e [MeV]

Time resolution – CERN May2010 START signal – quarz detector, resolution < 100 ps TDC gain – 50 ps / channel e MeV

Summary  detector prototypes tested by cosmic muons gamma beam pion/electron beam  results optimal detector configuration found detector energy resolution close to 5% at 1 GeV e/p separation better than the SHOWER detector, in combination with RPC excellent separation detector time resolution 215 ps (sigma)

Design Number of modules 150x6=900 Mass of one module of lead-glass 14 kg Total mass of cal kg E. Lisowski, TU Krakow

Cosmic test setup lead glass module trigger detectors count rate: ~ 20 particles / hour

σ/N mean = 5.4 % our data Cosmic muon ADC spectra K. Gollwitzer, PhD thesis, University of California at Irvine, 1993 Fermilab E760 Central Calorimeter σ/N mean ≈ 7 % OPAL e - 1 GeV N p.e. ≈ 1800  ≈ 5% E760 e - 1 GeV N p.e. ≈ 4250  ≈ 5% E760  ≈ 2 GeV N p.e. ≈ 2082  ≈ 7% module length 50 cm

PMT Tests PMT EMI 9903KB (1.5'') ~720 PMTs available 500 PMTs tested HV dependence of PMT response: PMT alone at HV=1500 and 1700 V, PMT with a gamma-source 22 Na at HV=1200, 1500, and 1700 V; The results for HV=1500 V: <500 mV 79 pieces of PMTs 16% 500 mV < U < 1500 mV 120 pieces of PMTs 1500 mV < U < 2700 mV 191 pieces of PMTs >2700 mV 110 pieces of PMTs

Energy resolution and hadron rejection of the OPAL end cap calorimeter Energy resolution of the OPAL lead glass modules is 5%/sqrt(E), E in GeV) Hadron rejection below 10 GeV was not measured.

Simulated e  spectra K. Lapidus