Presentation on theme: "Photon Physics with PHOS"— Presentation transcript:
1Photon Physics with PHOS International Workshopon Heavy Ion Physics at LHCPhoton Physics with PHOSat Center China of Normal UniversityInstitute of Particle PhysicsMay 21-24, 2008, Wuhan, ChinaToru Sugitate / Hiroshima Univ.
2Outline of the TalkPhoton sources and physicsLessons from RHICReality and strategy for the 1st yearsConclusion
3Time Line of the Universe Photons: the important probe to explore the nature
4Photons in pp & AA collisions pQCD photonsPrecise calc. w/ pQCDIsolated photonsOnly little abundancehadronic photonsCalc. w/ pQCD, eg. PYTHIAmeson decays in jetsParton Distribution Function (PDF)Subprocess cross sectioncalculated with pQCDFragmentationFunction (FF)prompt photons in AACalc. w/ Lattice QCDThermal photons: QGP and HGp~T~GeV
5Photon Physics in AA collisions Hadronization(Freeze-out)+ExpansionPre-equilibriumThermalizationQGP phase?Mixed phasedecay photonsdirect thermal photonsdirect pQCD photonsGlobal observables: Multiplicities, distributionsDegrees of freedom as a function of T: hadron ratios and spectra, dilepton continuum, direct thermal photonsEarly state manifestation of collective effects: elliptic flowEnergy loss of partons in quark gluon plasma: jet quenching, high pt spectra, open charm and open beautyDeconfinement: charmonium and bottonium spectroscopyChiral symmetry restoration: neutral to charged ratios, res. decaysFluctuation phenomena - critical behavior: event-by-event particle comp. and spectraGeometry of the emitting source: HBT, impact parameter via zero-degree energy flowpp collisions in a new energy domainGlobal observables: Multiplicities, distributionsDegrees of freedom as a function of T: hadron ratios and spectra, dilepton continuum, direct thermal photonsEarly state manifestation of collective effects: elliptic flowEnergy loss of partons in quark gluon plasma: jet quenching, high pt spectra, open charm and open beautyDeconfinement: charmonium and bottonium spectroscopyChiral symmetry restoration: neutral to charged ratios, res. decaysFluctuation phenomena - critical behavior: event-by-event particle comp. and spectraGeometry of the emitting source: HBT, impact parameter via zero-degree energy flowpp collisions in a new energy domainExperimental advantages of Photon Measurementa single calorimeter measures photons and neutral mesons.a calorimeter identifies particles up to very high momentumImportant physics outcome on DAY-1Most-cited single results from RHIC; 422 cited as of May 2008Suppression of hadrons with large transverse momentum in central Au+Au collisions at s(NN)**(1/2) = 130-GeV.By PHENIX Collaboration (K. Adcox et al.). Sep pp. Published in Phys.Rev.Lett.88:022301,2002 / e-Print Archive: nucl-ex/
6Lesson-1 from RHIC p+p->p0 + X KKP Kretzer h++h- p0 data vs pQCDp+p->p0 + Xhep-ex/ S.S. Adler et al.h++h-p0Find discrepancies in Au+Au from elementary processes at high pT.The low pT feature has been known at SPS and understood as nuclear effects.
7The Jet Quenching at RHIC Both neutral mesons and photons are essential probes for the jet quenching.陽子＋陽子衝突におけるジェット生成高運動量粒子ｸｵｰｸハドロン粒子多重生成（ジェット）真空原子核衝突におけるジェット抑制Suppression is very strong (RAA=0.2!) and flat up to 20 GeV/cCommon suppression for p0 and h; it is at partonic levele > 15 GeV/fm3; dNg/dy > 1100RAA at higher pT reveals new features.
8Systematic error is dominant. Lesson-2 from RHICSystematic error is dominant.
9Direct g via g* measurements First direct photon excess seen at PHENIXCompare direct g and g* at LHCPHENIX preliminarydecay photonsthermal photons:Schematic spectrumT0max ~ MeV !?T0ave ~ MeV !?The first promising result of direct photon measurement at low pT from low-mass electron pair analysis.Are these thermal photons? The rate is above pQCD calculation. The method can be used in p+p collisions.If it is due to thermal radiation, the data can provide the first direct measurement of the initial temperature of the matter.pQCD photonsschematic purpose only
10Another Ion Collider at CERN s = 14 TeV for proton + protonsNN = 5.5 TeV for Pb + PbsNN at LHC = 28 x RHIC =320 x SPS = 1000 x AGSＣＭＳ実験ＬＨＣ-ｂ実験ＡＴＬＡＳ実験ＡＬＩＣＥ実験
11Thermo-dynamic feature “Expected” Features at LHCQGP formationX 2 TRHICX RHICX 3-5 VFORHICX 3-5 QGPRHICdominant hard processheavy quark productionX 2000~2% at SPS~50% at RHIC~98% at LHCThermo-dynamic featurep~T~GeVThermal photon physicsHigh pT jet physicsHeavy flavor physics
12Photon Detectors at LHC Exp.ATLASCMSALICENameLAr BarrelLAr EndcapECAL(EB)ECAL(EE)PHOSEMCalStructureLiquid ArPWO + APD~80,000ch~18,000chPb + APDCoverage0<|h|<1.4,2p1.4<|h|<3.2,0<|h|<1.5,1.5<|h|<3.0,0<|h|<0.12,0.6p0<|h|<0.7,Dynamic Range20MeV-2TeVupto 4TeV5MeV-80GeV16MeV-250GeVGranularity x0.003x x x0.0500.025x x x0.0500.0174x0.0174to0.05x0.050.004x0.0040.0143x0.0143Res.10%/E0.5%2.7%/E0.55%5.7%/E3.3%/E 1.1%7%/E1.5%
13Simulation Studies Event display with AliRoot Background photon source map
14Lots of PCB/frame/pipes there ITS+TPC+TRD+TOFX/X0~”43%”80%
15Direct Photon Sensitivity Direct photon sensitivity (sig/noise) along two scenarios; with and without jet quenching.Thermal photonsgall/gdecthermal g enhanced rangesignal strength w/o quenchingSystematic error with a TRD/TOF holegall/gdecsignal strength with quenchingA hole in TRD/TOF for 3 central PHOS modules, reducing X/Xo=80% down to ~20%, open the thermal photon sensitive window down to 3-4 GeV.Thermal photon sensitive window
16PHOS Strategy in 1st LHC year Photon physics with PHOS is very promising from the 1st year, butThere are some issues to be cleared for the success:single warm PHOS in 2008small acceptance; less yield, higher mgg cutoff, and calibration strategylow LY/gain; larger missing energy, higher trigger threshold, and increase non-linearitypoor mgg resolution; increase sys. errors0See Yuri’s TF listMgg[GeV]01st Module as of 15 May, 2008Mgg[GeV]3 PHOS modulesgeometrical acceptance1 PHOS modulepT[GeV]0 & acceptance by Takashi IwasakipT[GeV]* students’ working version
17PHOS Strategy in 2nd LHC year p+p at 14TeV and 1st Pb+Pb run expectedInstall 3 cold PHOS modules for the 1st Pb+Pb runsassemble two modules by this fallbuild the air-tight shellsintegrate photon triggersLearn the spectrometer from p+p runsTune the spectrometer for the best energy and spatial performances to minimize the systematic uncertaintiesPhoton analysis in reality is not easy but fruitful output guaranteedSubgroups are now being formed in PWG4 under Yves;~1000 p0in 1-2 days500k p0/109 events w/ warm PHOSby HT“You are very welcome to join the p0 team.” said by Hisa Torii, the convener.
18ConclusionALICE is a versatile detector and PHOS is optimized for measurements of thermal photons and neutral mesons up to moderate energies.Physics scope with PHOS in the 1st LHC years;pT spectra of neutral mesons in pp and AASeek new physics at the energy frontier!Promising outcome comparing with pQCDRAA of neutral mesons & photons up to mod. pTPromising outcome from 1st yearsRAA in d+AIndispensable info. planned in 3rd year.Thermal photons from QGP/HGNeed good understanding of apparatus for accurate all photon and meson yields, and good AA runspion yield from p+p in 30days by LB