13/03/2007Gustavo Conesa Frascati EMCAL meeting 1/24 Gamma jet/hadron correlations Gustavo Conesa Balbastre

13/03/2007 Gustavo Conesa Frascati EMCAL meeting 2/24 Why  ? Study the properties of matter at high density and temperature with: Jets Partons (jets) suffer energy loss traversing the medium  Jet multiplicity and energy redistribution  Jet-Quenching Photons Production unperturbed by the medium  Prompt photons: Test QCD,  -jet events  Jet-Quenching Production modified or created in the medium  Fragmentation photons  Quenching  Bremstrahlung, Jet-conversion  Enhancement Decay photons (neutral mesons)  Observation of hadron suppression  Jet-Quenching Fragmentation  Jet Prompt  00

13/03/2007 Gustavo Conesa Frascati EMCAL meeting 3/24 Decay  vs Direct   p+p collisions: mainly pi0  A+A collisions: Jet-Quenching RHIC: N  > N  for p T > 10 GeV/c LHC: N  > N  for p T > 100 GeV/c  PID: Shower shape + Isolation cut.  0 = 0,01-0,1 Photon Yellow Report hep-ph/

13/03/2007 Gustavo Conesa Frascati EMCAL meeting 4/24 Identification of prompt  in PHOS Background Factor 5 suppression Signal Predicted rates

13/03/2007 Gustavo Conesa Frascati EMCAL meeting 5/24 AliAnaGammaDirect p T threshold candidate isolated if: no particle in cone with p T > p T thres p T sum in cone,  pT <  pT thres Two parameters define  isolation: Cone size   R  Returns if a cluster is isolated by 2 Isolation Cut methods candidate PHOS/EMCal ITS+TPC IP

13/03/2007 Gustavo Conesa Frascati EMCAL meeting 6/24 Identification of prompt  in PHOS Background Factor 5 suppression Signal Shower Shape + Isolation Cut Factor 5 suppression Signal Background Predicted rates

13/03/2007 Gustavo Conesa Frascati EMCAL meeting 7/24 Isolated prompt  spectrum in PHOS (1 nominal year)

13/03/2007 Gustavo Conesa Frascati EMCAL meeting 8/24 Isolated prompt  spectrum in PHOS (1 nominal year) Quenching (RHIC value) decreases systematic error.

13/03/2007 Gustavo Conesa Frascati EMCAL meeting 9/24  Hadron redistribution can be best measured in the Fragmentation Function... If we know E parton.  HI environment limits the precision on the energy of the reconstructed jet/parton: Measure E prompt   E parton Fragmentation  Jet Prompt  Why  -hadron/jet correlations?  Study medium modification in fragmentation function (R AA of FF) from isolated  -jet and isolated  -hadron correlations. 00  Medium effects redistribute (  qL) the parton energy, E parton, inside the hadron jet (multiplicity, k T ).^

13/03/2007 Gustavo Conesa Frascati EMCAL meeting 10/24 AliAnaGammaJet  Search identified prompt photon (PHOS/EMCal) with largest p T (E  > 10 GeV).   -jet analysis class  Strategy (event by event)  min  max leading Search leading particle (charged or  0 ):   -  leading  180º E leading > 0.1 E  R Reconstruct the jet: Jet energy: particles around the leading with p T > 0.5 GeV/c, inside a cone of R = 0.3. Select jet and construct FF with charged hadrons. 2 configurations: charged and neutral hadrons (TPC+ITS and EMCAL) and charged only (TPC+ITS). IP PHOS/EMCal EMCal TPC+ITS

13/03/2007 Gustavo Conesa Frascati EMCAL meeting 11/24  -jet correlations  in PHOS, 40 GeV jets Charged only charged+EM p-p p T, part > 0.5 GeV/c Charged only Charged + EM Pb-Pb p T, part > 2 GeV/c Charged+EM Charged Charged+EM Charged

13/03/2007 Gustavo Conesa Frascati EMCAL meeting 12/24  -tagged fragmentation function E  > 20 GeV/c; Central barrel+EMCal detect jet hadrons, PHOS  Pb-Pb collisions Background Signal HIC background Any neutral signal in PHOS z = p T, jet hadron /E  Isolated  identified in PHOS If signal is quenched

13/03/2007 Gustavo Conesa Frascati EMCAL meeting 13/24 Charged + EM  -tagged FF R AA With quenched  0 Systematic errors due to jet(  0 )-jet background Sensitive to medium modifications at low z if larger than ~5% in both configurations.

13/03/2007 Gustavo Conesa Frascati EMCAL meeting 14/24  -hadron correlations  We could do the same study in a simpler way: tagging hadrons opposite to the isolated .  Suggested by F. Arleo et al. in : JHEP 0609:015,2006, hep-ph/ JHEP 0411:009,2004, hep-ph/ hep-ph/

13/03/2007 Gustavo Conesa Frascati EMCAL meeting 15/24 F.Arleo et al. hep-ph/ = E parton  -hadron correlations

13/03/2007 Gustavo Conesa Frascati EMCAL meeting 16/24  Requirements for good measurement: Perturbative direct photons. At LHC p T  > GeV/c Perturbative hadron, no medium residues. At LHC p T  > 10 GeV/c Wide z range, ideally 0  z    Thus ideally : minimum p T  >> minimum p T  Reasonable counting rates At LHC p T  < 100 GeV/c  Study made for p T  >20 GeV/c and p T  >70 GeV/c. F.Arleo et al. hep-ph/  -hadron correlations

13/03/2007 Gustavo Conesa Frascati EMCAL meeting 17/24  -hadron correlation p T  > 70 GeV/c – p T  >10 GeV/c Most of the z interval... but limited counting rate. F.Arleo et al. hep-ph/ Theoretical FF

13/03/2007 Gustavo Conesa Frascati EMCAL meeting 18/24  -hadron correlation p T  > 20 GeV/c – p T  >10 GeV/c F.Arleo et al. hep-ph/ Theoretical FF No match with real FF... but good counting rate.

13/03/2007 Gustavo Conesa Frascati EMCAL meeting 19/24  -hadron correlation fragmentation  contribution Much larger fragmentation  component with p T  >20 GeV/c. Decay photons will contribute much more. Isolation of direct photons will reject both.

13/03/2007 Gustavo Conesa Frascati EMCAL meeting 20/24  -hadron correlation Quenching Don’t see expected suppression in all region. Weaker energy loss, but see larger z region.

13/03/2007 Gustavo Conesa Frascati EMCAL meeting 21/24 The study claims that better concentrate in p T  >70 GeV/c direct , and p T  >10 GeV/c, but our calorimeters acceptance reduce  counting rate:  PHOS  20< p T  < 40 GeV/c  EMCal  20< p T  < 60 GeV/c We have to investigate results at lower p T cuts. Basic yields for 5.5A TeV Pb+Pb collisions 1k/year

13/03/2007 Gustavo Conesa Frascati EMCAL meeting 22/24 AliAnaGammaHadron  Search identified prompt photon (PHOS or EMCal) with largest p T (E  > 20 GeV).   -hadron correlations class, created following François Arleo studies.  Strategy (event by event) : hadron Search for all charged hadrons (TPC+ITS) or neutral  0 (EMCal or PHOS): 90º<   -  hadron < 280º p T hadron > 10 GeV/c IP PHOS/EMCal EMCal/PHOS TPC+ITS

13/03/2007 Gustavo Conesa Frascati EMCAL meeting 23/24 Data production  Analysis tools prepared and in CVS Test and tune them with AliEn data.  Production scheduled: 14 TeV, PYTHIA kPyGammaDirect :  -jet events (annihilation and Compton)   over PHOS: Energy bins in GeV: [10,20], [20,30], [30,40], [40,50] and [50,infinity], 10k events per bin.   over EMCal: Energy bins in GeV: [10,20], [20,30], [30,40], [40,50], [50,60], [60,70] and [70, infinity], 10k events per bin. kPyJets : Jet-Jet events with fragmentation  production.  Modifications in AliGenPythia to force events with at least one  fragmentation photon in PHOS or EMCal.   0 in PHOS or EMCal.   and  0 must have p T > 5 GeV.  Energy bins in GeV: [30,36], [36,42], [42,50], [50,60], [60,72], [72,86], [86,104] and [104,infinity], 50k events per bin.  Next step: pp PYTHIA + PbPb 5.5 ATeV

13/03/2007 Gustavo Conesa Frascati EMCAL meeting 24/24 Outlook  Isolation cuts necessary to identify prompt direct . Preliminary study in PHOS worked well. Study in EMCal: Amaya, Delia and Gustavo   -jet correlation provides a good test on medium modifications: Preliminary study in PHOS worked well. Study in EMCal: Guénolé and Gustavo   -hadron correlation provides new insight in the study of medium modifications Optimum conditions would be at p T  > 70 GeV/c and p T  >10 GeV/c, but small statistics, p T  > GeV/c and smaller p T  cut might be OK, to be investigated. Study in EMCal: Amaya, Delia and Gustavo  Start of MC production in AliEn soon.