Valery Dormenev Institute for Nuclear Problems, Minsk Experiment PANDA. Electromagnetic calorimeter based on the improved Lead Tungstate (PbWO4) crystals. Valery Dormenev Institute for Nuclear Problems, Minsk Gomel, 23.07-03.08 2007 Valery Dormenev. XXI PANDA Meeting, Dubna, 2-6 July, 2007

Facility for Antiproton and Ion Research (FAIR) at GSI (Darmstadt, Germany) Double ring with 1100 m circumferences. Pulse intensity SIS100: 4*1013 proton per pulse at 29 GeV, 5*1011 U28+ ions per pulse at 1 GeV/u SIS300: 1.5*1010 U92+ ions per pulse at 35 GeV/u

Basic Data of High Energy Storage Ring (HESR) Antiprotons/protons storage and acceleration Experiment Mode High Resolution Mode High Luminosity Mode Target Pellet target with 4*1015 atoms/cm2 Momentum range 1.5 – 8.9 GeV/c 1.5 – 15.0 GeV/c Pulse intensity, s-1 1*1010 1*1011 Luminosity 2*1031 cm-2 s-1 2*1032 cm-2 s-1 Momentum resolution 1*10-5 1*10-4 Injection Valery Dormenev. XXI PANDA Meeting, Dubna, 2-6 July, 2007

The PANDA Physics Program Charmonium spectroscopy Exotics: hybrids, glueballs and other exotics Mesons in nuclear matter Hypernuclear physics D mesons physics

Objects of research

PANDA detector 2 T superconducting solenoid 2 T dipole magnet Pellet target with 4*1015 atoms/cm2 Valery Dormenev. XXI PANDA Meeting, Dubna, 2-6 July, 2007

PANDA electromagnetic calorimeter On lead tungstate scintillation crystals with increased light yield (PWO-II) photon detection with energy- high position- resolution time- a wide energy range: 10 MeV < Eg < 10 GeV located inside a superconducting solenoid (B = 2T) necessary crystal size: length 20-22X0=18-20 cm, cross section RM*RM=2.2*2.2 cm2 Total crystals number: Barrel: 11520 Endcap upstream: 816 Endcap downstream: 6864 PWO X0=0.89 cm RM=2.19 cm Valery Dormenev. XXI PANDA Meeting, Dubna, 2-6 July, 2007

Lead tungstate crystal (PbWO4) CMS-type properties Density, g/cm3 X0, cm RM, cm Zeff Decay time, ns Light yield temp. coef., %/0C Refraction index at 600 nm, no/ne LY rel. NaI:Tl, % Max. llum, nm 8.28 0.89 2.19 75.6 4 (95%) 15 (5%) 100 (< 1%) -1.9 2.30/2.16 1.3 440

Properties optimization of PWO crystals for PANDA EMC To detect low energy g-quanta light yield increase is necessary There are 3 way: 1) Growth technology optimization to suppress amount of structure defects 2) Crystal activation by La, Y ions to achieve optimal Light Yield/ Kinetics/Radiation Hardness relation CMS crystals have been optimized for high radiation hardness requirement. 3) Operation at low temperature INP team activities (present and future): Optimization of the PWO crystal growth technology CMS EMC (1992-2007) Development of PANDA EMC specification (2002-2006) Quality improvement (PWO-II) for PANDA (2003-2007) Spectroscopy studies of preproduction crystals (2004-2007) Beam tests with 3*3 and 5*5 matrix of PWO-II (2004-2008) Development of the monitoring system for calorimeter (2005-2008) Quality tests of PWO-II crystals for PANDA EMC (2008-2009)

Performed measurements Light Yield measurements at different temperatures and time gates to study LY and kinetics dependences Beam test measurements of 3*3 PWO-II crystals matrix with APD read out at 00 C to evaluate energy resolution

Light yield temperature dependence (1) factor 4.5 +250C -250C Time gate=4ms

Light yield temperature dependence (2) Fast enough time response at -250C

Beam test of 3*3 matrix of PWO-II crystals with Avalanche photodiodes readout (MAMI/ Mainz, Germany) 16 photon energies: 40.9-674.5 MeV, width DE ~ 2MeV Time gate=1 ms

beam

Energy response. Line shape. Eg=40.9MeV Eg=674.5 MeV 8 surrounding crystals S 9 crystals S 9 crystals 8 surrounding crystals Counts Central crystal Central crystal Energy, a.u.

Energy resolution Stochastic term For CMS ECAL :

Conclusions (1) Technology optimization of PWO-II crystals gives double increase of the Light Yield in comparison with CMS PWO crystals Cooling from +250C down -250C allows to increase the Light Yield in 4-4.5 times with 90% of the light collection in 200 ns at -250C Energy resolution at 00C of PWO-II with APD: stochastic term 1.21% (00 C) is better then 2.3% (+180C) for CMS EMC

Conclusions (2) Extrapolation of the energy resolution of the 3x3 matrix of PWO crystals with APD readout at 00C gives s/E=2.46 % @Eg=1 GeV Previous test results of the 3x3 matrix of PWO crystals with PMT readout at -250C gives extrapolated energy resolution s/E= 1.86% @Eg=1 GeV with 0.95 % stochastic term Unfortunately transversal shower leakage is large at 3*3 crystals matrix geometry

Future plans PROTO60 Beam tests: 60 PWO-II crystals of the PANDA EMC geometry with APD readout at -250 C Radiation hardness investigation at -250 C