D.Peressounko for the ALICE collaboration Hard Probes 2010, October 10-15, Eilat, Israel

 QCD constraints in new kinematic region  Baseline for the heavy ion run  Check for the energy loss in hot matter if it is created in pp collisions with high multiplicity D.Peressounko, Hard Probes ALICE can measure neutral mesons as - Two photons registered in calorimeters PHOS or EMCAL. - Two photons converted and registered in TPC (see talk of Kathrin Koch) - One photon converted and another registered in calorimeters

Hard Probes PHOS: |  |<0.125  : 100 o 3/5 installed EMCAL: |  |<0.7  : 100 o 2/5 installed PHOS: high-granularity photon spectrometer (20 X 0 ) 18k PbWO 4 crystals 2.2  2.2  18. cm 3 R ip =460 cm 5 modules 64  56 crystals each (3 installed) acceptance:  =100 , |  |<0.12 energy range: GeV EMCAL large aperture Pb-Sc electromagnetic calorimeter (20 X 0 ) 13k towers 6  6 cm 2. R ip =428 cm acceptance:  =100 , |  |< supermodules 24  48 towers each (4 installed) energy range: GeV

Hard Probes PHOS EMCAL  E /E (%)  x (mm) R ip (cm) ITS+TPC ~1 ~2 See poster A.Borissov for EMCAL details

Hard Probes EMCAL PHOS+ conversion PHOS  PHOS = 6.7±0.1 MeV/c 2  EMCAL =11.5±0.1 MeV/c 2  Conv+PHOS = 7.4±0.1 MeV/c 2

Hard Probes TeV: 215 Mevents analyzed 900 GeV: 10 Mevents analyzed Not efficiency corrected

Hard Probes PHOS EMCAL Conversion + PHOS Calorimeters show drop of efficiency at high p t due to cluster merging. Because of finer granularity PHOS can reach ~6 times larger pt without entering into cluster unfolding business. Converison + PHOS goes down to pt~0.4 GeV/c and does not reach efficiency drop up to 10 GeV/c and presently is limited by statistics.

Hard Probes Add 6% decalibration to ideally calibrated MC to reproduce data To be improved with next calibration Pretty flat m(p t ) dependence => good linearity MC: Ideal calibration

Hard Probes Good linearity before clusters start to merge (>~5 GeV/c) Non-final calibration results in non- optimal resolution

Hard Probes All 3 methods see eta meson peak and will extract eta spectrum PHOS EMCAL Conv.+PHOS Conversion + calorimeters technique is able to measure  down to very small p t ~1 GeV: limited by small S/Bg and statistics.

Hard Probes Eta peak on its place No pt dependence => good linearity PHOS EMCAL

Hard Probes PHOS Analyzed statistics ~200 Mevents allows to reach ~10 GeV/c for PHOS and ~15 GeV/c for EMCAL EMCAL Not efficiency corrected

 Presently de-calibration is  ~6% in PHOS (calibration using slope equilibration in all channels)  ~10% in EMCAL (calibration using MIP peak)  We expect improvement in calibration down to 1 % after completing calibration using  0 peak  PHOS/EMCAL L0 Triggers have been commissioned, ready to run  After analysis of all statistics collected in 7 TeV pp run (~800 Mevents) we expect   0 spectrum measured up to 30 GeV/c   spectrum up to 20 GeV/c Hard Probes

 ALICE has excellent possibility to measure  0 and  in wide p t range  Several alternative methods provide a reliable cross- check  At the end of pp run of 2010 we expect that ALICE will measure  0 spectrum in the range GeV and  in the range 2-20 GeV/c  Important improvements such as PHOS and EMCAL L0 triggers will increase range in future runs Hard Probes