Direct Photon Production in ppcollisions at the LHCE.M. Liu IOPP/CCNU, Wuhan.China第8届高能物理大会分会2010.4.18南昌
Direct Photon Production in pp collisions at the LHC 第8届高能物理大会分会 2010.4.18 南昌 F.M. Liu IOPP/CCNU, Wuhan, China
2Main projects on photons at LHCAll 4 detectors of LHC have photon detectorsThey can measure photons from some hundred MeV tosome hundred GeVGoals:1) SM Higgs search via Higgs -> gamma gamma2) Measure fragmentation function in pp via gammatriggered events, and study QGP properties in AAHere I am talking about another goal:1)QGP formation in pp?2) Determine the dynamics for parallel scattering in pp
Main projects on photons at LHC • All 4 detectors of LHC have photon detectors • They can measure photons from some hundred MeV to some hundred GeV Goals: 1) SM Higgs search via Higgs -> gamma gamma 2) Measure fragmentation function in pp via gamma triggered events, and study QGP properties in AA Here I am talking about another goal: 1) QGP formation in pp? 2) Determine the dynamics for parallel scattering in pp 2
3outlinepp collisions at extremely high energy (i.e. 14TeV)Multiple scattering, many Pomerons / strings involvedHow to treat the afterward secondary scattering?Direct photon productionRHIC Au+Audata are explained with 4 sourcesHydrodynamic description of the hot dense matter in AAHydrodynamic treatment of the secondary scattering in ppResults and discussionpQCD+plasmacontributionIs it possibletoform a QGP in pp collisions?PHOS@ALICE will answer. pt 100Mev~100GeV
outline • pp collisions at extremely high energy (i.e. 14TeV) – Multiple scattering, many Pomerons / strings involved – How to treat the afterward secondary scattering? • Direct photon production – RHIC Au+Au data are explained with 4 sources – Hydrodynamic description of the hot dense matter in AA – Hydrodynamic treatment of the secondary scattering in pp • Results and discussion – pQCD + plasma contribution – Is it possible to form a QGP in pp collisions? PHOS@ALICE will answer. pt 100Mev~100GeV . 3
4Hadron production in ppp+p:88Usually,apairofstringsare formed:&XPYTHIA,HIJINGaDPM,FRITIOF,VENUS,NEXUS,.88b)Chadronproduction: string fragmentation,i.eqqOMBB
Hadron production in pp Usually, a pair of strings are formed: PYTHIA, HIJING, DPM, FRITIOF, VENUS, NEXUS,. hadron production: string fragmentation, i.e. 4
5pp collisions at high EProblem:Two-stringpicture cannotexplainobservables(~1ooGeV)1) High multiplicity (multiplicity dis. predicted is too narrow)2) Increaseof mean pt3) High pt jets4) Rise of central rapidity densitySolution: Multiple scattering becomes important at high energiesMorePomerons/stringsareaddedXXJUUUVUUUUUUPomeron = a pair of stringsUUUUUUUUUUUUUUUUUXUUWUUUProb(y), V : Pomeron numberH.J.Drescher et al, Phys.Rept.350,93(2001)F.M.Liu et al.PRD 67, 034011 (2003)(a)(b)
pp collisions at high E Problem: Two-string picture can not explain observables (~100GeV) 1) High multiplicity (multiplicity dis. predicted is too narrow) 2) Increase of mean pt 3) High pt jets 4) Rise of central rapidity density Solution: Multiple scattering becomes important at high energies More Pomerons/strings are added Pomeron = a pair of strings Prob(𝜈)， 𝜈： Pomeron number F.M.Liu et al. PRD 67, 034011 (2003) H.J.Drescher et al, Phys.Rept.350,93(2001). 5