EMCal PPR Photons section 070309 EMCal PPR Photons

EMCal PPR: Photons section 07/03/09 EMCal PPR: Photons 1/22

Proposed table of content Blue: Close to be finished Green: Under progress. Some work previously done that could be used but new simulations are helpful Red: Not for the next 2 months, need new simulations and time. 07/03/09 EMCal PPR: Photons 2

Task: Pi 0 (eta) invariant mass analysis n In charge: n n n In a first moment Jocelyn (Sergei). Student, cannot dedicate full time. This is the most important physics topic for the first runs. Need to define a group of people to work on this now. n n n Acceptance, efficiency, corrections to be estimated p. T reach for different EMCal configurations and different running times … Analysis task code already available and working. Min bias generation is produced now in the grid, suitable for this study, need Pb. Pb RAA extraction …? 07/03/09 EMCal PPR: Photons 3

Task: Pi 0 invariant mass analysis in EMCal, e+-e- in TPC n n In charge: Raphaëlle? Code is ready n n Photon converts in ITS and e+e- pair measured in TPC. Analysis code for converted photon reconstruction developed Ana Kenneth et al and available. n n n e+ e- Need to implement in next weeks the converted photon AOD output. Matching between this code and cluster in calorimeter available in Part. Corr frame. Need to tune the code, see the feasibility of the method: p. T reach, resolution etc 07/03/09 EMCal PPR: Photons 4

Task: Photon identification via conversion and signal in PHOS, Single particle TRD/TOF n n n New identification procedure suggested by Nicola In charge: We proposed to a master Brazilian student but not available in the next months. Idea: Photon convert in material in front of EMCal, in TRD and TOF. The shower will also produce signal in the detectors. n n A photon is a bigger cluster, or several clusters in the calorimeter with a match in the TRD and TOF and no match in the TPC. PHOS, Single particle + Hijing I did a similar study with PHOS 5 years ago but in this case the charged signal from the shower is given by the CPV n n At least 60% of converted photon, combination of 2 “electrons”, were tagged as converted photons both in pp and Pb. Pb environment. Material and many things have changed. 07/03/09 EMCal PPR: Photons 5

Direct photons and isolation cuts: Generators predictions n n n In charge: Amaya Poster in QM, presentation in PWG 4 Main conclusions: n n n Comparison between Herwig and Pythia, no detector effects, ideal conditions, open geometry Jets and fragmentation photons are less produced in Herwig, at a maximum of a factor 2 Fragmentation function very similar. Prompt photons are similarly produced, at maximum a 20% more with Herwig. Sum of fragmentation+prompt photons give similar cross section to NLO calculation (Jet. PHOX) Isolation Cuts: n n 07/03/09 Similar isolation trends for different particle species In general a shift of about 10% in isolation, HERWIG underlying event is smaller, less isolated particles. EMCal PPR: Photons 6

Direct photons and isolation cuts: Reevaluation of isolation cuts n n In Charge: Gustavo Nothing new: pp @ √ 14 Te. V n n Pb. Pb @ √ 5. 5 Te. V, qhat = 50 I could try to extrapolate the missing points, knowing the input background spectrum and the isolation and identification rejection factors. Add a systematic error coming from the generator studies. Problem, old simulations, PID better than now … Need new data. 07/03/09 EMCal PPR: Photons 7

Direct photons and isolation cuts: Isolation efficiency study in a model free measurement n n In charge : Raphaëlle? Method 1: Event by Event Pi 0 identification with 2 photons in the calorimeter n n n Method 2: Pi 0 identification via shower shape n n Need to see up to which p. T this is feasible, reasonable counting rate. More than 10 Ge. V difficult Code available Feasible between 10 and 40 Ge. V Code available Raphaelle is looking to it, see her presentation in PWG 4 Method 3: Event by Event pi 0 identification, photon in EMCal, photon reconstructed in TPC n n Need to study feasibility Code that connects calorimeter and TPC photon reconstruction is available 07/03/09 EMCal PPR: Photons 8

Direct photons and isolation cuts: RAA n Direct photons suppression due to: n n n RHIC Isospin Nuclear Parton distribution functions Fragmentation photons suppression due to jet-quenching With isolated photons we should be sensitive to cold nuclear matter suppression effects (isospin n. PDF) Without isolation, it will involve more work considering the statistical extraction of the decay photon yield, etc. LHC Prediction suppression photons directs au LHC F. Arleo et al. ar. Xiv: 0707. 2320 v 1 [hep-ph] 07/03/09 EMCal PPR: Photons 9

Gamma-jet correlation n In charge: Guenole is gone so Gustavo, code not available, only my old code that should be updated with Guenole’s improvements. Remaining questions: n n Improve UE subtraction Include systematic error due to jetjet. 07/03/09 EMCal PPR: Photons Pb. Pb/pp n 10

Gamma-Jet (Jet finder) correlation n n Standard jet algorithms energy measurement can be calibrated with gamma-jet events ( not considering k. T effect) “Small” acceptance of EMCal, and “tiny” of PHOS makes it difficult. Study feasibility in pp and Pb. Pb and how to apply this corrections. Code that connects isolated photon and jet found with JETAN (package with different algorithms) is available. In charge: Gustavo 07/03/09 EMCal PPR: Photons 11

Gamma-Hadron correlation n n No need to reconstruct the jet to construct a meaningful fragmentation function In charge: Yaxian? preliminary 8<p T trigger< 16 Ge. V/c, p. T asso > 3 Gev/c EPJC (2008) 57: Y. Mao et al. z. T=0. 9 z. T=0. 3 Tomographie de la collision! XN Wang ar. Xiv: 0902. 4000 v 1 [nucl-th] 07/03/09 EMCal PPR: Photons 12

Backup 07/03/09 EMCal PPR: Photons 13

Conversions in front of EMCal LHCC response High conversion in TOF and TRD 07/03/09 EMCal PPR: Photons 14

Conversions in front of EMCal LHCC response Overlapped Pi 0 misidentification via Shower shape Photon identification via Shower shape 50 -60% of converted photons not identified 07/03/09 Overlapped photon pairs misidentified as photons does not change for converted photons EMCal PPR: Photons 15

Conversions in front of EMCal LHCC response Normalized Pi 0 invariant mass does not change much in case of conversions 07/03/09 EMCal PPR: Photons 16

PID: Shower shape single cut with ellipse main axis Study for CD 2 Cynthia Hadjidak identified : 02 < 0. 25 identified 0: 02 > 0. 25 For energies larger than 10 Ge. V, 0 produce most likely a single cluster, try to separate 0 and via shower shape. p+p Pb+Pb Ndirect g / Ng from p 0 g identified as g 0 gg identified as as p p 0 Ndirect g / Ng from p 0 PID efficiency p+p 14 Te. V p 0 as g p. T (Ge. V/c) Need to be revised since digitization and reconstruction parameters have changed New Task for Amaya? 07/03/09 EMCal PPR: Photons central Pb+Pb 5. 5 Te. V factor 5 p 0 suppression p. T (Ge. V/c) 17

Task: PID bayesian with shower shape analysis n n In charge: Marie Germain Shape of clusters λ 02 (main axis of the cluster ellipsoide) + Bayesian analysis to determine probability for a cluster to be originating from ( , π0, hadron). Now in Ali. Root, parametrization for pp events found with old Ali. Root version with different digitization parameters. PID determination: n n Generation of 10000 single particles ( , 0, k. L 0) Merged single events with HIJING Pb. Pb at 5. 5 Te. V Only EMCal present in the simulation Fit of λ 02 distributions: Gaussian + landau Distribution n Gaussian: Norm. G * TMath: : Gaus(λ 02 , m. G, σG ) : 3 parameters Landau : Norm. L* TMath: : Landau(λ 02 , m. L, σL ): 3 parameters Evolution of each parameter with Energy is fitted by: n 07/03/09 Param (E(Ge. V)) = p 0 E-2 + p 1 E-1 + p 2 + p 3 E + p 4 E 2 EMCal PPR: Photons 18

Task list Task Sub Task Comments Who PID Re-evaluate PID shower shape parameters with last Ali. Root version Evaluate different parameters for pp and Pb. Pb Marie Pi 0/Eta invariant mass analysis Study acceptance, reconstruction efficiency, p. T reach study, RAA. With and without PID Jocelyn Photon identification via conversion in TRD/TOF Match signals in TRD/TOF with EMCAL clusters not matched in the TPC Gustavo EMCAL (gamma) - Central barrel (conversion) combination for Inv, Mass of pi 0 Study feasibility, p. T reach, possible background. Gustavo Compare predictions for different generators and theory Direct gamma, pi 0 decay spectra predictions. Isolation efficiency in both cases. Pythia done. Study Herwig or other. Amaya Direct photons Isolation cut Re-evaluate IC with larger amount of events, specially jet-jet, (PYTHIA) IC efficiency model free estimation 1) Pi 0 identified in calorimeter 2) Pi 0 identified in EMCAL and TPC Gamma-jet Gustavo Raphaelle? 2) Only if fourth item shows good statistics RAA, estimate systematic errors of measurement Gustavo Improve HI background rejection Gustavo Estimate effect of jet-jet contamination after Isolation Cut Gustavo Standard Jet algorithm calibration in pp/Pb. Pb Gamma-hadron Study feasibility and background subtraction correlation 07/03/09 Compare gamma-jet FF and energy reconstruction and JETAN jet reconstruction in pp. Needs last gamma-jet code available. Gustavo Yaxian? EMCal PPR: Photons 19