Open charm analysis with the ALICE detector in pp collisions at LHC

Abstract

The upcoming ALICE experiment, at the Large Hadron Collider located at CERN, is designed to investigate the physics of strongly interacting matter at very high energy densities. In this thesis we present an analysis strategy for the feasibility of reconstructing open charm mesons with ALICE via the hadronic decay of D0 and D* mesons. Heavy flavours, produced at the The Large Hadron Collider in unprecedented amounts, are excellent tools to investigate the properties of the hot and dense QCD medium produced in heavy-ion collisions. Baseline measurements of heavy flavour production mechanisms in pp collisions are necessary in order to understand the production in the medium as well as medium induced effects. The study shows that for one year of data taking we will be able to measure charmed mesons with very large significances (78 for D0 and 33 for D?). Both yields allow a measurement in one month of data taking (about 100 million events) with a D? significance of 10. The reconstruction of the charged mesons is more difficult than for the neutral mesons due to kinematic constraints on the soft pion in case of the D* decay. Most of these pions have momenta lower than 0.4 GeV/c which makes them difficult to detect and therefore the reconstruction efficiency is very low. However, by using the ALICE Inner Tracking System as a standalone detector, the reconstruction efficiencies for kaons and pions at very low momenta are improved. Kaon reconstruction improved by 10% and soft pion detection by 16%. Due to selection criteria imposed on the tracks the overall efficiency increase for the D* with the ITS-standalone procedure is reported to be 7%. It is important to note that after applying the cuts on the D mesons, the contamination with D0 from beauty decays becomes slightly larger (10%). For analyses where high efficiency is preferred over high purity, the cuts on the D* and D0 can be loosened in order to have as many particles as possible. In this case, a review of the contamination from B decays is needed.