Study Of The Heavy Flavour Production Via Hadronic And Semi-muonic Channels With ALICE At The LHC

Our human being has never been stopping in the exploration of the virgin field in understanding ourselves and our surroundings. Some of fundamental questions of nature are to study the regular and the interaction of particles. According to the pre-diction of Standard Model, it explains that the fundamental particles are three genera-tions of quarks, three generations of leptons and four force carriers (γ-electromagnetic interaction, gluon-strong interaction, W±, Z0-weak interaction). Strongly interacting force between quarks is exchanged by a kind of gauge particle named gluon. Due to the colour confinement, quarks and gluons are restrained in hadron. From the calcu-lation of lattice Quantum Chromo-dynamics (LQCD) a deconfined phase transition from hadron to quark-gluon plasma (QGP) state will occur. Studying the properties of the QGP phase will directly test the prediction of LQCD and reveal the regular of the strong interaction. And the deconfined phase is thought to have constituted the few μs-old Universe. Therefore the experimental detection of QGP signal can also help us to understand the evolution of the Universe.In the experimental laboratory, nucleus-nucleus(A-A) collisions allow to form the condition of high energy density and/or high baryons density, are the unique tool available to investigate phase transition of QCD matter. A lot of work has been devoting to the exploration of the medium in last30years. The running Large Hadron Collider (LHC) will contribute to such study to increase the center-of-mass energy of a factor30with respect to RHIC. ALICE (A Large Ion Collider Experiment) is one of the four experiments at LHC, its goal is to study of nucleus-nucleus collisions at center-of-mass energy of5.5TeV per nucleon-nucleon (N-N) pair, studying the chiral symmetry restoration and the deconfinment phase transition. The initial runs with proton-proton collisions at900GeV (2009) and7TeV (2010) are as base line, provide useful reference points for the Pb-Pb collisions at center-of-mass energy of 2.76TeV (2010) and5.5TeV (in future).Up to now, the suppression of high momentum hadron and V2of the hadron in final state are observed in RHIC, which indicate that the phase transition of QCD matter. The deep deconfined matter formed in Pb-Pb collisions at LHC, which leads to study the properties of the strong interactions more optimistic. Due to the hard process will be dominant at LHC energies (~98%hard process), a good opportunity to use the tomograph is supported. Heavy quarks are sensitive probes of the medium produced in nucleus-nucleus collisions, because they are produced in the early stage of the collision in primary partonic scatterings, through the QCD energy loss mechanisms when they propagate in the medium. Measurements of heavy quark production in p-p collisions (2010and2011, center-of-mass energy of7TeV) serve as important tests forperturbative Quantum ChromoDynamics (pQCD) and offer the baseline for A-A collisions (center-of-mass energy of2.76TeV,2010and2011). This work mainly reports the heavy flavour production in p-p collision with the simulation at center-of-mass energy of14TeV and real interaction at center-of-mass energy of7TeVChapter1devotes to report the introduction of physics motivation to study de-confinement matter at LHC/ALICE, the heavy flavour physics at LHC energies, and the previous experimental results for heavy flavour measurement at SPS and RHIC. The structure and principle of the ALICE detectors which are used for simulation framework of this study on experimental simulation, particle tracking reconstruction and data analysis are presented in Chapter2.Chapter3shows the rescontruction of heavy flavour in p-p collison at center-of-mass energy of14TeV. We developed CDF/Tevatron used impact parameter fitting method to subtract secondary D*meson which decay from beauty. In the LHC/ALICE experiments, due to internal track system (ITS) allows high-resolution, reconstruction of the short-lived mesons to be possible in the cyclotron. At the same time, D*meson which decay from beauty occupy substantial percentage (about15%) at the high transverse momentum district, which constitute a serious background with respect to the primary signal. This chapter will be to promote the use of impact parameter fitting method in Tevatron experiments for the background substraction in LHC/ALICE, which leads to enhance the significal reconstruction of primary D*meson and more precise reflect the kinematical properties of charm quarks.Chapter4presents the main results obtained in p-p collisions at (?)=7TeV are: inclusive differential production cross section of muons from heavy flavour decay, pt distribution in whole η region (－4<η <－2.5) and in5η bins, and η distribution in2<pt <12GeV/c. Finally the results are compared with FONLL predictions, lie in the upper limit of the model predictions, they are good agreement with each other within errors. And chapter5reports the main results obtained in Pb-Pb collisions at (?)=2.76TeV:the production high transverse momentum of heavy flavour decay muons at forward rapidity, in Pb-Pb collisions at (?)=2.76TeV. The nuclear modification factor, in－4<η <－2.5region, is studied as a function of transverse momentum and collision centrality. A weak suppression is measured in peripheral collisions, in the most central collisions, a strong suppression is observed, providing a clear evidence for heavy quark in-medium modifications. And first attempt to extract W±.