Frankfurt 2014 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 5: Schwerionenkollisionen und QCD Phasen

HK 5.1: Talk

Monday, March 17, 2014, 14:00–14:15, HZ 7

A Bayesian approach to PID in ALICE, as studied in the channel D0 -> Kπ — •Jeremy Wilkinson — Physikalisches Institut, University of Heidelberg, Im Neuenheimer Feld 226

The standard particle identification (PID) method in ALICE uses a frequentist, or nσ, approach. In this method, particles are accepted via a selection on the number of standard deviations by which a signal differs from the expected detector response. This works well for most particle species, but in some cases, such as the non-resonant decay of Λc -> pKπ, the combinatorial background is too high to make a significant measurement. The usage of an alternative Bayesian approach, based on a combination of the measured dE/dx and time-of-flight of the daughter tracks, will be presented here. The Bayesian method bases its response on prior probabilities of a given particle species being produced with a given momentum, allowing a calculation of the probability for a daughter particle to belong to each species (π, K, p, etc.) based on the detector response seen. In order to check the validity of this method, various decay channels were tested and compared to the nσ method. Among these was the channel D0 -> Kπ, which provides a valuable cross-check of both the kaon and pion responses in this approach. In addition to considering the differences in signal-to-background ratio and significance obtained when applying the various methods, a comparison will be shown between the yield obtained without PID and those found when using Bayesian and nσ approaches after being corrected for their respective PID efficiencies.