Measurement of $\Lambda_{\rm c}$ Baryon production in the decay channel $\Lambda_{\rm c} \rightarrow p \rm K^{0}_{\rm S}~$ in proton-proton and proton-lead collisions with ALICE detector at LHC

This thesis describes the study of the production of the charmed baryon $\Lambda_{\rm c}^{+}$ in proton-proton and proton-lead collisions with the ALICE experiment, operating at the Large Hadron Collider (LHC) at CERN. ALICE was built to study hadronic collisions (pp and A-A) and, in particular, aims to investigate the $Quark-Gluon Plasma$ (QGP), state of the matter during the first instants of life of the universe. When two ultra-relativistic heavy nuclei collide, the extreme conditions of temperature and pressure, necessary for the QGP formation, can be created. In particular, heavy quarks (charm and beauty) are produced in hard scattering processes during the first stages of the hadronic collision. The measurement of hadrons with heavy quarks in pp collisions at the LHC energies is a powerful test for perturbative quantum cromodynamics (pQCD) in this energy domain. Moreover, these studies are the necessary reference for studying the production of heavy quarks in nucleus-nucleus collisions. Results from pp and p-Pb collisions constitute the needed reference in order to disentangle initial-state cold nuclear matter (CNM) effects) from QGP related effects. The thesis describes the analysis strategy developed and used to measure the $\Lambda_{\rm c}^{+}$, through the reconstruction of the decay channel $\Lambda_{\rm c}^{+} \rightarrow p K^{0}_{\rm S}$, using invariant mass studies. The analysis has been performed using two data samples: $\sim$ $3\times10^8$ events in pp collisions at $\sqrt{s}$ = 7 TeV and $\sim$ $10^8$ events in p-Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV, collected with the ALICE detector in 2010 and 2013, respectively. All the relevant results are shown, from the $\Lambda_{\rm c}^{+}$ signal extraction in several intervals of transverse momentum, to the measurement of the $prompt$ (i.e. coming from direct hadronization of quark charm) $\Lambda_{\rm c}^{+} $ production cross section. The results are compared with those obtained with other analyses performed in ALICE using different analysis strategies and different $\Lambda_{\rm c}^{+} $ decay channels in both the pp and p-Pb samples. The results presented in this thesis have been recently published by the ALICE Collaboration and already presented at several national and international conferences.