The Photon Spectrometer for RHIC and beyond

1. 20×20× 200 mm3 produced by Furukawa co. T.Sugitate Y.Furuhashi K.Homma R.Kohara T. Sugitate / Hiroshima / PHX031 / Nov.01 The Photon Spectrometer for RHIC and beyond PbWO4 Crystal Density 8.29 g/cm3 Radiation length 0.89 cm Moliere radius 2.2 cm Presented by Toru Sugitate Hiroshima University

2. T. Sugitate / Hiroshima / PHX031 / Nov.01 Motivation of the project • Motivation • Photon 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 work • Choice 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 costs • To be discussed in the workshop.

3. T. Sugitate / Hiroshima / PHX031 / Nov.01 A PWO signal for a MeV photon PMT Hamamatsu R7056 single photon sensitive (107 @1900V) PWO crystal (Covered with Aluminum) 60Co -source PMT Hamamatsu R2083 plastic scintillator BC-404

4. T. Sugitate / Hiroshima / PHX031 / Nov.01 PWO light yield and decay time constant Pulse height distribution Scintillation decay curve Sample (B) single p.e. peak double p.e. peak 60Co- photo peak Time spectrum [ns]

5. T. Sugitate / Hiroshima / PHX031 / Nov.01 A beam test with 150 MeV electron at the Hiroshima VBL A 150 MeV electron microtron and a storage ring

6. Geant4 simulation of a 150 MeV electron injection in a crystal Single electron peak Ee = 116 MeV Deposit energy 77 % Energy resolution 16 % The simulation does not include; photon and p.e. statistics, backgrounds, PMT and electronics noises, and the beam energy fluctuation. double electron peak Ee = 231 MeV Ee = 117 MeV /E = 13 % T. Sugitate / Hiroshima / PHX031 / Nov.01 Crystal response to the 150 MeV electrons

7. T. Sugitate / Hiroshima / PHX031 / Nov.01 A Monte Carlo simulation of the PWO photon spectrometer GEANT4 Simulation 10 0 ’s in the acceptance (dN/d~76) d/dpexp(-p/0.3) (1<p<5 GeV/c) flat distribution in y and  π0 → γγ The Photon Spectrometer coverage: 1m ×1 m crystal size: 20×20×200 mm3 array size: 50 × 50 distance from IP: 3 m  coverage: 0.17

8. The invariant mass spectrum shows the mass reconstruction resolution of 3.2% A sophisticated clustering algorithm may considerably improve the mass resolution . Invariant Mass [MeV/c2] T. Sugitate / Hiroshima / PHX031 / Nov.01 Invariant mass spectrum Deposit Energy vs. Hit Position at the PWO Spectrometer

9. T. Sugitate / Hiroshima / PHX031 / Nov.01 Snapshots of APD readout from the crystal Blue-enhanced APD Hamamatsu S5345 active area: 5mm  Photon signal for 137Cs source Charge amplifier Hamamatsu H4083 Gain: 0.5V/coulomb

10. T. Sugitate / Hiroshima / PHX031 / Nov.01 Summary and outlook of the “Hiroshima” project Summary • A 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 • A MC simulation code was setup. • APD readout underway. Outlook in 1.5 years • Build 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.