PHOS in ALICE

1. PHOS in ALICE A PHOton Spectrometer with unique capabilities for the detection/identification of photons and neutral hadrons China - ALICE meeting

2. PHOS China - ALICE meeting

3. Rails for PHOS China - ALICE meeting

4. What is PHOS ? • PHOS is a photon spectrometer consisting of • A high resolution, highly granular EM calorimeter • Associated to a MWPC acting as a charge particle veto detector, • … offering unique particle detection • With high energy resolution (~ 1.5% @ 10 GeV) • And high position resolution (~ 1.25mm @10 GeV) • And particle identification from very low (0.5 GeV) to fairly high (100 GeV) transverse momentum: • Direct photon • Decay photon • Electrons • Charged hadrons • Neutral hadrons (p0 and h) • Neutral baryons (n and n) China - ALICE meeting

5. Position resolution Energy resolution • a = 0.013 ± 0.007 GeV • b = 0.036 ± 0.002 GeV1/2 • c = 0.0112 ± 0.0003 Detection with PHOS China - ALICE meeting

6. Identification with PHOS 1/3 • Photons Shower topology Efficiency 90% Purity 5% China - ALICE meeting

7. p0 h Invariant mass Identification with PHOS 2/3 • Soft neutral hadrons (pt < 20 GeV/c) China - ALICE meeting

8. Identification with PHOS 3/3 • Hard direct photon (pt > 20 GeV/c) Shower topology & isolation cut China - ALICE meeting

9. PHOS provides access to an unique scientific program • Dynamical characterization of the medium by its radiation spectrum: • Early hard QCD processes: initial state structure (hard photons and neutral hadrons @ pt 20-100 GeV/c) • Hot partonic phase (Quark-Gluon Plasma) • Thermal EM radiation (black body, photons @ pt < 2 GeV) • Medium effects on jets (jet quenching, p0 @ pt > 10 GeV/c, jet photon tagging) • Late hadronic phase (soft photons and neutral hadrons) • To study soft QCD effects and medium effects • Hadrons gas – partons gas phase transition • Chiral symmetry restoration • Gluon saturation China - ALICE meeting

10. Photon production @ LHC Decay photons Prompt photons China - ALICE meeting

11. PHOS hardware • Elementary detection cell • PWO4 crystal: 22  22180 mm3 (20 X0) • Photo-readout: Avalanche Photo-Diodes (APD) • Modular structure • 17920 lead-tungstate crystals (PWO) • 5 independent modules each of 3584 crystal detector units: • Total area: 8m2 • Total crystal weight: 12.5t China - ALICE meeting

12. PHOS FE & RO electronics • A challenging project: convert weak light signal into energy and time signals and construct trigger signals. • Energy • Dual gain energy channels and digitization for covering a very large dynamic range up to ~100 GeV • Separate fast energy signal for trigger and timing • Time • Resolution ~2 ns to discriminate against low energy baryons • Trigger • L0 (< 900 ns) for min-bias pp, low threshold (100 MeV) • L1 (< 6.2 ms) for high pT Pb-Pb, high threshold (5-10 GeV) China - ALICE meeting

13. ALICE DDL (optical) DAQ PC EVENT DATA Ethernet DCS CONTROL PHOS L0/L1 ALICE Trigger System Optical links, coax ALICE L0/L1/L2/TTC Cabling PHOS power + bias 400V, 12V, 6V, 3.3V PHOS FEE & RO electronics in ALICE FEE PWO crystals Counting room area China - ALICE meeting

14. energy 4 x 8 crystals trigger control PHOS FE & RO electronics: details ALICE DAQ Trigger DCS FEE board 32 crystals Trigger/ Router Board TRU RCU data control L0, L1 China - ALICE meeting

15. T card (Bergen & Kurchatov) • Connection to FEB • 2  2  8 analog signals UV Photon Detector • Avalanche Photodiode from Hamamatsu • 55 mm2 • C ~ 80 pF at 250 V bias • Preamplifier (Bergen & Kurchatov) • Sensivity 1V/pC • Noise 470 e- • Rise time 10 ns • Dynamic range 1mV – 8 V China - ALICE meeting

16. FEE board 32 channels T cards • Functions: • Shaper/amplifier: slow dual gain outputs for energy, fast energy output for trigger • Energy digitization (10 bit, base-line restoration, zero suppression) • Quadlet (2x2) analog summing of fast energy signals for PHOS trigger • Timing • APD bias control (2%)+ other control channels China - ALICE meeting

17. Trigger Router Card 448 channels • Functions: • Data and Control GTL cable bus with FEE’s and RCU • Digitization of quadlets from FEE boards • PHOS L0/L1 Trigger generation • Router for event data stream via RCU to ALICE DAQ China - ALICE meeting

18. Readout Control Unit • Functions: • Main Controller, DDL to ALICE DAQ, • DCS Ethernet • Provides timing information China - ALICE meeting

19. energy 4 x 8 crystals trigger control PHOS FE & RO electronics: Status ALICE DAQ Trigger DCS FEE board 32 crystals Trigger/ Router Board TRU RCU • R&D for a few elements has ended • Most of the elements in design/development phase • There is a lot of work in all areas • Designed as state-of-the-art technologies (programmable logic) • Construction sites not yet defined data control L0, L1 China - ALICE meeting

20. PHOS collaboration • China: • Beijing, China Institute of Atomic Energy • Wuhan, Huazhong Normal University, Institute for Particle Physics • Czech Republic: • Prague, Academy of Science of the Czech Republic, Institute of Physics • France: • Nantes, Laboratoire de Physique Subatomic et des Technologies Associées • Norway: • Bergen, University of Bergen, Department of Physics • Oslo, University of Oslo, Department of Physics • Poland: • Warsaw, Soltan Institute for Nuclear Studies • Russia: • Moscow, Russian Research Center ‘Kurchatov Institute’ • Protvino, Institute for High Energy Physics • Sarov, Russian Federal Nuclear Center ‘VNIIEF’ • Dubna, Joint Institute for Nuclear Research China - ALICE meeting