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HK: Fachverband Hadronen und Kerne

HK 33: Heavy Ion Collisions and QCD phases

HK 33.7: Talk

Tuesday, March 17, 2009, 18:30–18:45, H-ZO 10

Reconstruction of π⁰ and η mesons through photon conversions for pp data at LHC — •Kathrin Koch¹, Kenneth Aamodt², and Ana Marin³ — ¹Univ. Heidelberg, Physik. Institut, Germany — ²University of Oslo, Norway — ³GSI Darmstadt, Germany

In 2009 the CERN LHC starts with a short run of pp collisions at the injection energy of 0.9TeV followed by a longer run of 10TeV. First PbPb collisions at √s_NN=5.5 TeV are expected at latest in 2010. The pp run provides important reference data for the heavy-ion runs. One of the most important observables in heavy-ion collisions are direct photons, because they give information about the high temperature and the high density phase. The main background for direct photons are photons from π⁰ and η decays. Therefore, high precision measurements of their spectra are necessary to extract the direct photon spectrum. Independent from electromagnetic calorimeters this can be done with the reconstruction of photon conversions in the high resolution central tracking system. This method gives a very good mass resolution on the order of 5MeV. Simulations show that one month of pp minbias collisions results in a p_t reach of 25GeV for π⁰ and 12GeV for η assuming an integrated luminosity of 13nb⁻¹. The statistics are comparable to that reached with the PHOtonSpectrometer (PHOS), and the method can also be used for PbPb collisions. In this talk an overview will be presented about the reconstruction method and the expected p_t spectra for different integrated luminosity scenarios.