Observation of the production and decay of particles in the forward region at the LHCb experiment

This thesis is structured around two main studies, namely a study of Monte Carlo hadronic collisions generators and an LHCb data analysis. In the first study, the predictions of PYTHIA [1], EPOS [2], QGSJET [3], and SIBYLL [4], all with tunes based on ``central" rapidity measurements from the LHC general purpose detector experiments, i.e. ATLAS [5], ALICE [6] and CMS [7], are compared to ``forward" rapidity measurements of observables in $pp$ collisions at $\sqrt{s}=7$ TeV from LHCb [8] and TOTEM [9]. These measurements fall into four categories, namely energy flow [10], charged hadron multiplicities and densities [11-13], charged hadron production ratios [14] and $V^{0}$ hadron production ratios [15]. The results of the study are published in [16]. The overarching conclusion of the study is that the tuning in the ``central" region improves the predictions in the ``forward" region, too, but tuning with measurements from the latter is necessary for better descriptions therein [16]. The measurements of prompt $V^{0}$ ($K_{S}^{0}$ and $\Lambda^{0}$) production cross-sections and ratios in $pp$ collisions at $\sqrt{s}=13$ TeV are the subject of the LHCb data analysis. The measurements are carried out in a two-dimensional phase space of rapidity and transverse momentum, divided into a $6\times6$ array of symmetric bins in $2\leq y<5$ and $1\leq \log{(p_{T} [\text{MeV/c}])}<4$. The full analysis phase space values of the cross-sections are $\sigma_{K_{S}^{0}}={64501}.5 \pm {4787}.3$ \textmu b, $\sigma_{\Lambda^{0}}={22106}.3 \pm {1656}.3$ \textmu b and $\sigma_{\overline{\Lambda^{0}}}={21013}.7 \pm {1654}.3$ \textmu b. For the $\overline{\Lambda^{0}}/\Lambda^{0}$ and $\overline{\Lambda^{0}}/K_{S}^{0}$ ratios, values of $0.960 \pm 0.052$ and $0.329 \pm 0.023$, respectively, have been obtained. The quoted uncertainties are the quadratic sum of the statistical and systematic uncertainties, with the former being comparatively negligible. This latter work represents the stem of a future LHCb analysis note.