Cynthia HadjidakisTerzo Convegno sulla Fisica di ALICE Detection of photons and electrons in EMCAL Photons, Electrons and  0 at large p T Identification of photons and  0 with EMCAL Detection of electrons in EMCAL Cynthia Hadjidakis Terzo Convegno sulla Fisica di ALICE Wednesday, November 14, 2007

Cynthia HadjidakisTerzo Convegno sulla Fisica di ALICE Photons,  0 and electrons at large p T Direct photons prompt photons hard processes: compton (g q   q) and annihilation (q q   test QCD production unperturbed by the medium  -jet events Neutral mesons via decay photons detection medium effect  observation of hadron suppression in Heavy Ion collisions Electrons from semi-leptonic decays of b and c quarks medium effect  different suppression for light and heavy quarks in Heavy Ion collisions _

Cynthia HadjidakisTerzo Convegno sulla Fisica di ALICE Calorimetry in ALICE PHOS:  = 0.24,  =100º Distance to I.P 4.40 m high granularity: crystals E > 10 GeV   E/E < 1.5% 11 Super Modules 2 SM per 20 o sector EMCAL  = 1.4,  = 110 o Distance to I.P 4.28 m granularity: towers  ×  ~ 0.014×0.014 E>10 GeV   E/E < 4% Y X

Cynthia HadjidakisTerzo Convegno sulla Fisica di ALICE EMCal and high p T physics EMCAL capabilities:  inclusive jets : E T ~ 200 GeV  dijets: E T ~ 170 GeV  inclusive   : p T ~ 90 GeV/c   inclusive  : p T ~ 70 GeV/c   + jet p T ~ 40 GeV/c  e (semi-leptonic decay of heavy quarks ): p T ~ 25 GeV/c 10k/year Annual yields in ALICE with EMCAL

Cynthia HadjidakisTerzo Convegno sulla Fisica di ALICE Identification of photons and  0 in EMCAL p T < ~ 10 GeV/c10 ~ < p T < ~ 40 GeV/c merged cluster → shower shape analysis resolved clusters → invariant mass analysis small aperture angle isolation cut → talk by Gustavo   R TPC candidate IP three regions of analysis

Cynthia HadjidakisTerzo Convegno sulla Fisica di ALICE  0 reconstruction via invariant mass → effect of the HI environment: efficiency decreases (<10%) → measured  0 yield as input of simulation to obtain the decay  distribution → measurement of direct  efficiency only EMCAL ● single particles ○ + HI  events  1  2 invariant mass (GeV) simulation for pp and PbPb conditions high occupancy in PbPb: increase cluster energy threshold 100 MeV (pp) → 500 MeV (PbPb)  m        GeV simulation: single particles+HI only EMCAL - single particles + HI

Cynthia HadjidakisTerzo Convegno sulla Fisica di ALICE Shower shape analysis 0, longest axis of cluster ellipsoid Bayesian method developed for the PID based on a parametrization of 0 , e-  ° charged hadrons  0 27 GeV fit: Landau+Gaussian 0 2 dn/d 0 2 Guénole Bourdaud

Cynthia HadjidakisTerzo Convegno sulla Fisica di ALICE   rejection (     ) about 5 N direct  /N  from NLO calculations: → isolation cut needed to improve   rejection Shower shape analysis → HI environment: lower efficiency (10 to 20%) → Identification of  and  0 from ~10 GeV to ~40 GeV with this method (preliminary results: studies with realistic background needed) ppPbPb PID for  0 PID for  efficiency/purity simulation: single particles full ALICE flat  and  0 distributions

Cynthia HadjidakisTerzo Convegno sulla Fisica di ALICE Detection of electrons in EMCaL track matching: each charged track is associated with a EMCAL cluster (if any) → add ALICE PID information from EMCAL to high p T charged tracks (TRD  rejection for high p T ) simulation: single particles full ALICE Alberto Pulvirenti Mark Heinz, Jennifer Klay, Alex Donoghue p TPC / E EMCAL

Cynthia HadjidakisTerzo Convegno sulla Fisica di ALICE Electron identification →  rejection of

Cynthia HadjidakisTerzo Convegno sulla Fisica di ALICE Photon Conversion Center of Collision Time Projection Chamber EMCAL Inner Tracking System TRD and TOF 50% of photons convert into e + e - → 45% of photons convert into TRD and TOF → removed by p/E cut Other sources of background: photon conversion and Dalitz decay X (cm) Y (cm)

Cynthia HadjidakisTerzo Convegno sulla Fisica di ALICE Conclusion EMCAL improves ALICE capabilities to measure high p T photons, electrons and  0 Direct photons and  0 measurements Identification with invariant mass technique up to p T ~ 10 GeV/c Identification with shower shape analysis up to p T ~ 40 GeV/c Isolation cut to improve   rejection and for higher p T region Detection of electrons Electron identification and good  rejection with track matching