the photon spectrometer for rhic and beyond

T. Sugitate / Hiroshima / PHX031 / Nov.01

The Photon Spectrometer for RHIC and beyond

PbWO4 CrystalDensity 8.29 g/cm3

Radiation length 0.89 cm Moliere radius 2.2 cm

Presented by Toru Sugitate

Hiroshima University

Y.Furuhashi T.SugitateK.Homma R.Kohara

20×20× 200 mm3

produced by Furukawa co.


Motivation of the project

MotivationPhoton is an unique signal to explore the QGP matter.

higher granularity in a large multiplicity environment. higher energy resolution for better PID capabilities. PWO crystal is a good candidate for the EMCal upgrade.

Scope of the workChoice of the crystal; Apatity, Shanghai, Japan.Optimize the optical readout device; PMT, PIN, APD.Design and fabricate a FEE prototype.Prototyping of an array and testing with beams.Physics measurements in a RHIC experiment.

Time profile and costsTo be discussed in the workshop.


A PWO signal for a MeV photon

PMT Hamamatsu R7056

single photon sensitive (107 @1900V)

PWO crystal(Covered with Aluminum)

60Co -source

plastic scintillatorBC-404

PMTHamamatsu R2083


PWO light yield and decay time constant

single p.e. peak

Scintillation decay curve

Sample (B)

double p.e. peak

60Co- photo peak

crystal Light Yield [p.e./MeV] Decay Time [nsec] Light outputs in 50 ns

PWO (A) 4.5 1.5 (23%)+5.0 (72%)+21.9 (5%) 97.8 %

PWO (B) 8.2 1.2 (16%)+5.9 (81%)+38.2 (3%) 94.9 %

BGO 404 185 23.7 %

Time spectrum [ns]

Pulse height distribution


A beam test with 150 MeV electron at the Hiroshima VBL

A 150 MeV electron microtron and a storage ring


Ee = 117 MeV/E = 13 %

Crystal response to the 150 MeV electrons

Deposit energy 77 %Energy resolution 16 %

double electron peak Ee = 231 MeV

Single electron peak Ee = 116 MeV

Geant4 simulation of a 150 MeV electron

injection in a crystal

The simulation does not include; photon and p.e. statistics, backgrounds, PMT and electronics noises, and the beam energy fluctuation.


A Monte Carlo simulation of the PWO photon spectrometer

The Photon Spectrometercoverage: 1m ×1 m

crystal size: 20×20×200 mm3

array size: 50 × 50distance from IP: 3 m

coverage: 0.17

π0 → γγ

GEANT4 Simulation

10 0 ’s in the acceptance (dN/d~76)

d/dpexp(-p/0.3) (1<p<5 GeV/c)

flat distribution in y and


Invariant mass spectrum

Deposit Energy vs. Hit Position at the PWO Spectrometer

The invariant mass spectrum shows the mass reconstruction

resolution of 3.2%

Invariant Mass [MeV/c2]

.A sophisticated clustering

algorithm may considerably improve the mass resolution


Snapshots of APD readout from the crystal

Charge amplifierHamamatsu H4083Gain: 0.5V/coulomb

Blue-enhanced APDHamamatsu S5345active area: 5mm

Photon signal for 137Cs source


Summary and outlook of the “Hiroshima” project

SummaryA crystal produced by Furukawa was tested:

Transmission; 50%@350nm and 80%@400nm. Light yield; 4-8 p.e./MeV. Decay constant; 1=1.2-1.5ns (16-23%), 2= 5.0-5.6ns

(72-81%), and 3= 21.9-38.2ns (3-5%). Light output in 50 (100) ns; 94.9 (98.6)%. Energy deposit in 20x20x200mm: 77% consistent with

Geant4

Outlook in 1.5 yearsBuild a mini-tower (3x3) in this Dec. Mini-tower tests with PMT at Hiroshima and at

KEK-PS. Improve the clustering algorithm in the MC

code.Continue to study the APD readout.Evaluation of crystals from Apatity and Shanghai.Mini-tower tests with APD readout in the next JFY. Optimization of APD device.

A MC simulation code was setup. APD readout underway.

the photon spectrometer for rhic and beyond

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