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QM2006 Daicui Zhou

PHOSPHOS, the ALICE PHOPHOton SSpectrometer

• The scientific objectives

• The design

• Status & Performance

Daicui Zhou(for the ALICE/PHOS Collaboration)

Institute of Particle Physics, Central China Normal University, Wuhan,China

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The role of photons

– Jet quenching first observed through high pt 0 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

PHENIX Phys. Rev. Lett. 88 (2002) 022301

WA98, Phys. Rev. Lett. 85 (2000) 3595

PHENIX, Nucl-Exp/0605005

• SPS and RHIC data have shown the importance of the photon signal to diagnose the properties of matter formed in heavy-ion collisions.

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… and at LHC• Extending the photon measurement in the very hard regime ( ~ 100

GeV/c)• More favorable environment for direct photon identification (larger /

0, isolation cuts)• Provide a calibration of the jets through photon-tagged jet measure

ments• A hotter and longer lived QGP should emit a measurable thermal ra

diation

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Requirements

• High quality photon identification in a hadron dominated environment (dN/dy ~ 2000-4000)– CPV for h± and e± - discrimination– time of flight for h (mainly n and n) - discrimination– Shower shape and isolation cut for 0 - discriminati

on

• 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

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ALICE-PHOS Detector

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

ALICE

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Technical data

• 17920 PWO crystals• distance to IP: 4.6m

• coverage in pseudo-rapidity:

|| < 0.12• coverage in azimuthal angle:

< 100°• crystal size: 22×22×180 mm3 • Depth ： 20X0 • photo readout: APD + CSP• operating temperature: -25 oC

PHOS Module

Avalanche Pin-Diode

Crystal

Preamplifier

moduleSupport structure

Strip unit

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Readout and electronics

112 FEEs / 8 TRUs / 4 RCUs / 3584 CSP-APD

Cold volume: • PWO strips 2x16=32 channels array • APD+CSP

FEE boards working at room temperature

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Signal Processing Scheme

NIM A565(2006) 768CERN/ALICE 99-4, ALICE TDR2

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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 CERN from June-Sept 2006

FEE Card

FEE card hardware properties

FEE Card

•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) 768CERN/ALICE 99-4, ALICE TDR2

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ALICE-PHOS first Module

3584 crystals 112 FEE cards

1st Module beam test at PS-T10

First PHOS moduleCooling system

Assistant cooling

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Calibration Stability

Gain 1 / Gain 2

• 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

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Energy and Position resolution

<(E)/E> ~ 3%, ((E)/E) ~ 0.1% @ 2 GeV <x> ~ 2.7mm @ 2 GeV

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Timing and Mass Resolution

(0) =4.7 MeV/c2

+ 12C → 0 + X → 2 + X

Invariant mass spectrum

~ 0.5 ns at E > 1.5 GeV

Timing resolution measurement with the electron beam. Standard start-stop method with an external trigger

Hysayuki Torii’s poster for ALICE-PHOS(138)

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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

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ALICE-PHOS project-organization- China, Beijing, China Institute of Atomic Energy- China, Wuhan, Central China Normal 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 !

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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