Münster 2017 – wissenschaftliches Programm
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HK: Fachverband Physik der Hadronen und Kerne
HK 12: Heavy Ion Collisions and QCD Phases III
HK 12.4: Vortrag
Dienstag, 28. März 2017, 12:00–12:15, F 1
Determination of secondary particles contamination in charged particle spectra measured with ALICE at LHC — •Federica Sozzi for the ALICE collaboration — GSI, Darmstadt, and Universität Heidelberg
Transverse-momentum distributions for primary charged particles and corresponding nuclear modification factor RAA have been measured by the ALICE Collaboration for different collision systems and energies, comprising newer data sets collected in Run 2 and re-analysed data sets from Run 1.
The systematic uncertainties are largely reduced with respect to similar past ALICE measurements, due to improvements in the analysis procedure. One of the systematic contribution that has been studied is the contamination of secondary particles in the sample, originating from the interaction of particles with material and, to a larger extent, from the weak decay of neutral strange particles, K0 and Λ. The fraction of secondaries after the track selection cuts is of the order of few percent and depends on the transverse-momentum. Since the yield of the strange particles is known to be underestimated in event generators, the determination of this fraction from MC leads to a corresponding large uncertainty. Therefore the fractions of secondaries have been determined through fits of the experimentally-measured distributions of the distance to closest approach of tracks to vertex. In this contribution the fitting method, the results and their impact on the transverse-momentum distribution measurement will be described.