PHOS , the ALICE PHO ton S pectrometer

1. PHOS, the ALICE PHOton Spectrometer The scientific objectives The design Status & Performance Daicui Zhou (for the ALICE/PHOS Collaboration) Institute of Particle Physics, Central China Normal University, Wuhan,China QM2006 Daicui Zhou

2. PHENIX Phys. Rev. Lett. 88 (2002) 022301 The role of photons • SPS and RHIC data have shown the importance of the photon signal to diagnose the properties of matter formed in heavy-ion collisions. • Jet quenching first observed through high ptp0 suppression • Observation of high pt direct photon, constraining pQCD • Observation of low pt photon excess which could be interpreted in terms of thermal photons emission WA98, Phys. Rev. Lett. 85 (2000) 3595 PHENIX, Nucl-Exp/0605005 QM2006 Daicui Zhou

3. … and at LHC • Extending the photon measurement in the very hard regime ( ~ 100 GeV/c) • More favorable environment for direct photon identification (larger g/p0, isolation cuts) • Provide a calibration of the jets through photon-tagged jet measurements • A hotter and longer lived QGP should emit a measurable thermal radiation QM2006 Daicui Zhou

4. Requirements • High quality photon identification in a hadron dominated environment (dN/dy ~ 2000-4000) • CPV for h± and e± - g discrimination • time of flight for h (mainly n and n) - g discrimination • Shower shape and isolation cut for p0 - g discrimination • This can be provided by • A high granularity EM calorimeter providing excellent energy and position resolution and timing measurement • Associated to a charged particle detector QM2006 Daicui Zhou

5. ALICE-PHOS Detector ALICE EMCA: 5 arrays of 56×64 Lead tungstate crystals (small radiation length and Moliere radius) CPV: multi-wire chamber with pad readout matching the granularity of EMCA PHOS QM2006 Daicui Zhou

6. Avalanche Pin-Diode Crystal Strip unit Preamplifier module Support structure Technical data • 17920 PWO crystals • distance to IP: 4.6m • coverage in pseudo-rapidity: |Dh| < 0.12 • coverage in azimuthal angle: DF < 100° • crystal size:22×22×180 mm3 • Depth： 20X0 • photo readout: APD + CSP • operating temperature: -25 oC PHOS Module QM2006 Daicui Zhou

7. Readout and electronics • Cold volume: • PWO strips 2x16=32 channels array • APD+CSP • FEE boards working at room temperature 112 FEEs / 8 TRUs / 4 RCUs / 3584 CSP-APD QM2006 Daicui Zhou

8. Signal Processing Scheme NIM A565(2006) 768 CERN/ALICE 99-4, ALICE TDR2 QM2006 Daicui Zhou

9. FEE Card • 32 channel FEE card • V1.0 prototype in Aug. 2004 and test beam at CERN • V1.1 version in Jan. 2005 and review in May 2005 • 130 cards production and testing at Wuhan in Jan 2006 • Commissioning and test beam at CERNfrom June-Sept 2006 FEE card hardware properties • 32 ch.dual gain shapers τ=1μs • RMS noise 2 us: 615 e-(3.1MeV) • 14 bit dyn range 5 MeV-80GeV • 32 APD bias regulators ±0.1V • Fast OR (2*2 Xtals) for trigger • Board controller FPGA (PCM) • USB controller • TPC-like readout and control bus • DAQ and DCS via RCU • 5.5 Watt,349*210 mm2 NIM A565(2006) 768 CERN/ALICE 99-4, ALICE TDR2 FEE Card QM2006 Daicui Zhou

10. QM2006 Daicui Zhou

11. 1st Module beam test at PS-T10 3584 crystals 112 FEE cards Cooling system First PHOS module Assistant cooling ALICE-PHOS first Module QM2006 Daicui Zhou

12. Calibration Stability • The balance test of ratio of different APD channels was carried from 2 calibrations runs under the condition that the prototype was warmed up and cooled down again • The balance value of ratio of the gains: • Mean  0.99 •   0.02 Gain 1 / Gain 2 QM2006 Daicui Zhou

13. Energy and Position resolution <(E)/E> ~ 3%,((E)/E) ~ 0.1% @ 2 GeV <x> ~ 2.7mm @ 2 GeV QM2006 Daicui Zhou

14. Timing resolution measurement with the electron beam. Standard start-stop method with an external trigger Invariant mass spectrum + 12C → 0 + X → 2 + X ~ 0.5 ns at E > 1.5 GeV (0) =4.7 MeV/c2 Timing and Mass Resolution Hysayuki Torii’s poster for ALICE-PHOS(138) QM2006 Daicui Zhou

15. Installation plan • The first PHOS module will be installed in ALICE for the first pp run in 2007 • The 2nd and 3rd modules will be installed during the first winter shutdown after pp run • The 4th and 5th modules will be installed for the first long heavy-ion run QM2006 Daicui Zhou

16. ALICE-PHOS project-organization - China, Beijing, China Institute of Atomic Energy - China,Wuhan,Central ChinaNormal University, Institute for Particle Physics - China,Wuhan, Huazhong University of Science and Technology - Czech Republic,Prague, Academy of Science of the Czech Republic, Institute of Physics - Germany,Münster, Westfälische Wilhelms Universität, Institute für Kernphysik - Japan, Hiroshima, Hiroshima University - Norway, Bergen, University of Bergen, Department of Physics - Norway, Oslo, University of Oslo, Department of Physics - Poland, Warsaw, Soltan Institute for Nuclear Studies - Russia, Moscow, Russian Research Center ‘Kurchatov Institute’ - Russia,Protvino, Institute for High Energy Physics - Russia, Sarov, Russian Federal Nuclear Center ‘VNIIEF’ - Russia, Dubna, Joint Institute for Nuclear Research - Switzerland, Geneva, CERN All the PHOS colleagues are acknowledged for the slides Thanks ! QM2006 Daicui Zhou

17. Importance of the TOF • Different time resolutions of the TOF system were studied to estimate the contamination of the photon spectrum by hadrons. TOF 2ns/E reduces significantly the contamination from hadrons below ~0.1 QM2006 Daicui Zhou