CERN Accelerating science

The thesis is performed in the context of the ALICE experiment dedicated to the study of quantum chromodynamics and especially of the quark-gluon plasma (QGP) through ultrarelativistic heavy ion collisions at the LHC (CERN). The thesis addresses the production of the beauty-meson $\mathrm{B}^0 (\mathrm{d} \bar{\mathrm{b}})$ through the decay channel $\mathrm{B}^0 \to \left( \mathrm{D}^- \to \pi^- \mathrm{K}^+ \pi^- \right) \pi^+$ in proton-lead (resp. proton-proton) collisions with a center-of-mass energy $\sqrt{s_{\rm NN}} = 5.02$ TeV (resp. $\sqrt{s} = 13.6$ TeV) with the ALICE detector, during LHC Run 2 (resp. Run 3), in domains of midrapidity ($|y_{\rm lab}| < 0.5$) and low to high transverse momentum ($2 < p_{\rm T} < 24 $ GeV$/c$). The first measurement of the production cross section of $\mathrm{D}^-(\mathrm{d} \bar{\mathrm{c}})$ mesons, originating from a beauty-hadron decay in proton-lead collisions at midrapidity, allows for the establishment of the nuclear modification factor of these mesons, providing an indirect probe towards the study of nuclear effects impacting $\mathrm{B}^0$ mesons, and not due to QGP. The analysis workflow of this beauty meson, developped during this thesis in new ALICE software, is also presented and validated via measurements of $\mathrm{B}^0$ mesons production rate in simulated data. This analysis workflow, applied to real data from proton-proton collisions of LHC Run 3, made possible the first observation of $\mathrm{B}^0$ meson signal via full topological reconstruction in the ALICE collaboration. The results obtained establish necessary references to characterise QGP-induced effects on the beauty-meson production.