Heidelberg 2015 – wissenschaftliches Programm

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HK: Fachverband Physik der Hadronen und Kerne

HK 48: Poster

HK 48.28: Poster

Mittwoch, 25. März 2015, 17:00–19:00, C/Foyer

Estimating Hadron Contamination of Electron Samples in Pb--Pb Collisions at Low Momenta Using ALICE — •Martin Braß for the ALICE collaboration — Physikalisches Institut, Universität Heidelberg, Germany

A Large Ion Collider Experiment at the LHC is exploring a new state of matter at high energy densities in Pb--Pb collisions. Electrons from heavy-flavor decays are interesting probes of the properties of this state, since charm and beauty quarks - produced in initial hard scatterings - experience the whole evolution of the state. Due to high multiplicities in Pb--Pb collisions and to the limited separation power of the ALICE Time-Of-Flight (TOF) detector between electrons and pions at momenta above 1 GeV/c, there is a large hadronic background in the observed electron samples. Furthermore a significant amount of protons, kaons and deuterons are misidentified by TOF and contaminate the electron sample, too. Many Heavy-Flavor-Electron analyses rely on a precise estimation of the contamination. The presented analysis uses measured energy loss distributions of the ALICE Time Projection Chamber as templates for a least squares fit routine to estimate the amount of hadronic background in the electron sample at momenta above 0.4 GeV/c. To describe the energy loss distributions of the misidentified particles, the measured distributions of particles which are identified by TOF are used. The energy loss distribution for pions is obtained using the ALICE Transition Radiation Detector which provides good separation between pions and electrons.