Study of inelastic processes in proton-proton collisions at the LHC with the TOTEM Experiment

The TOTEM experiment, located into the CMS cavern at the CERN Large Hadron Collider (LHC), is one of the six experiments that are investigating high energy physics at this new machine. In particular TOTEM has been designed for TOTal cross-section, Elastic scattering and diffraction dissociation Measurements. The total proton-proton cross-section will be measured with the luminosity-independent method based on the Optical Theorem. This method will allow a precision of 1÷2% at the center of mass energy of 14 TeV. In order to reach such a small error it is necessary to study the p-p elastic scattering cross-section (dσ/dt) down to |t|∼ 10^−3 GeV^2 (to evaluate at best the extrapolation to t = 0) and, at the same time, to measure the total inelastic interaction rate. For this aim, elastically scattered protons must be detected at very small angles with respect to the beam while having the largest possible η coverage for particle detection in order to reduce losses of inelastic events. In addition, TOTEM will also perform studies on elastic scattering with large momentum transfer and a comprehensive physics programme on diffractive processes (partly in cooperation with CMS), in order to have a deeper understanding of the proton structure. For these purposes TOTEM consists in three different sub-detectors: two gas based telescopes (T1 and T2) for the detection of inelastic processes with a coverage in the range of 3.1 ≤ |η| ≤ 6.5 on both sides of the interaction point 5 (IP5), and silicon based detectors for the elastically scattered protons, located in special movable beampipe insertions called Roman Pots (RPs), at about 147 m and 220 m from the interaction point. The work done by the candidate reported in this thesis mainly consists in three subjects: the tuning of the simulation for the T2 inelastic telescope, the study of the noise of the T2 detector and a preliminary study concerning the detection perfor- mance for inelastic events. In the following, the first chapter describes the TOTEM experiment and the LHC machine, with a particular attention to the T2 telescope and its analysis software, being of critical importance for the work of this thesis. The second chapter introduces the physics programme of the TOTEM experiment. Chapter three describes the tuning of Geant4 parameters and the improvement of the simulated geometry for the T2 detector, while chapter four summarizes an im- portant and demanding study on the detector noise. Finally in chapter five some preliminary studies on inelastic processes are presented, in order to show the per- spective for the TOTEM experiment to perform the measurement of the inelastic cross section in a wide kinematic range.