Study of prompt and secondary D meson decay with the ALICE experiment

From Monday 30 th June to Friday 22 nd August, 2014, I attended the CERN summer student training program 2014. The program introduces various useful knowledge, culture exchanges and scientific skills to my experiences. I attend in the mornings lectures, especially on theoretical topics. Furthermore, I gained fruitful skills on computational methods, concretely ROOT/AliROOT and C++ Language. I have been guided to most of experiments and detectors including ALICE, CMS and ATLAS detectors and I have also attended different workshops. A major source of uncertainty in the analysis is the unknown fraction of secondary D0 mesons coming from b-hadron decays, which has been estimated on the basis of perturbative QCD predictions and a range of hypotheses for the b-hadron nuclear modification factor is estimate. The project consists in studying whether topological variables sensitive to displacement with respect to the primary vertex, larger for secondary D–mesons, can be used to extract the fraction of D mesons from b-hadron decays in a data driven method and specify only pPb since the work is only for pPb collisions. In particular, the selection cuts were studied to compute the raw signal of D mesons with an invariant mass analysis. Selection and reconstruction efficiencies were considered with the detector acceptance, to correct for experimental effects by using a Monte Carlo simulation (MC). We applied different cuts of normalized decay length L xy and points angle θ xy , to study the effect of these cuts on the invariant mass spectra and efficiencies