Inclusive charged hadrons production in pp collisions with the ALICE-HMPID detector at the LHC

The goal of this thesis is the study of the particles identification provided by a small acceptance detector: the High Momentum Particle IDentification detector. Installed during September 2006 and located at about 5 m from the primary vertex, it can contribute to several ALICE physics items using the Cherenkov radiation. This thesis is made of 5 chapters. An overview of the Heavy Ion collisions, the Quark Gluon Plasma, and the main points of the ALICE physics program are described in the first chapter. Some recent results on particles production and hadron ratios are also presented. Chapter 2 is dedicated to the LHC machine, to the ALICE apparatus and to the High Momentum Particle Detector. The layout, the principle of operation and some recent performance results of this RICH detector will be described. Chapter 3 is dedicated to the evaluation of the HMPID PID efficiency. This study exploit the unique possibility to extract the efficiency directly from data using the V$^{0}$ ’s decay. Also, it provides a comparison with Monte-Carlo simulation. A detailed description of this study is presented. In addition, the measurement of the refractive index of the C$_{6}$F$_{14}$ radiator in the HMPID chamber has been carried out. The main topic of the thesis is presented in Chapter 4. The measurement of the pions, kaons and protons spectra and hadrons ratios (π$^{−}$/π$^{+}$ , K$^{−}$ /K$^{+}$ and $\bar{p}$/p) in pp collisions at sqrt(s) = 7 TeV is presented. All the correction factors, MC and data comparison and systematics uncertainties will be described. The results will be discussed and compared with previous experiments. The end of this thesis (Chapter 5) is dedicated to work in progress item: the HMPID analysis in pp collisions at sqrt(s) = 2.76 TeV. Preliminary raw spectra and ratios will be presented.