Tracking and Particle Identification at LHCb and Strange Hadron Production in Events with Z Boson

The Lhcb experiment, located at the Large Hadron Collider at CERN, is a high energy particle physics experiment dedicated to precision measurements of events containing beauty and charm quarks. The detector is built as a single-arm forward spectrometer. It uses tracking stations upstream and downstream of its dipole magnet to measure the trajectories and momenta of charged particles. This thesis describes the improvements to the track reconstruction algorithm, which were implemented for the second run of the LHC that started in spring 2015. Furthermore, the method to confirm the performance numbers on data is presented. In addition to the tracking system, the detector uses two Ring Imaging Cherenkov detectors, upstream and downstream of the dipole magnet, together with the calorimeter and muon system, for particle identification. The detector response for the particle identification is known to be poorly modelled, since the dependence on environmental variables like temperature and pressure inside the gas moderators are difficult to simulate. This thesis presents a tool for the correction of the particle identification detector responses using calibration data. With higher collision energy and luminosity the understanding of the soft part of a proton-proton interaction becomes more and more important for high precision measurements at LHC. The soft part includes, for example, the understanding of fragmentation and hadronisation processes, which need experimental input. This thesis presents the first measurement at LHCb of the production of $K^0_s$ and $\Lambda / \bar{\Lambda}$, both hadrons that contain a strange quark, in an event containing a Z boson. The decay channels $Z \rightarrow \mu^+\mu^-$ , $K^0_s \rightarrow \pi^+ \pi^-$, $\Lambda \rightarrow p\pi^-$ and $\bar{\Lambda} \rightarrow \bar{p}\pi^-$ were used. The measurements were performed as function of the opening angle between the Z boson and the strange hadron, as well as the transverse momentum $p_T$ of the latter. The data collected by LHCb $pp$ collisions corresponds to an integrated luminosity of 2fb$^{-1}$ at a centre of mass energy of 8 TeV. The results are compared to Monte Carlo predictions from PYTHIA.