Prompt and non-prompt J/Psi cross-sections in proton-proton collisions at sqrt(s) = 5.02 TeV with ALICE

Abstract

The study presented in this thesis is about the measurement of \jpsi\ production in proton-proton collisions at center-of-mass energy \(\sqrt{s}\) = 5.02 TeV with the ALICE detector at the LHC, with a focus on the separation between prompt \jpsi\ and non-prompt \jpsi, the latter originated from beauty-hadron decays. Statistics collected during 2017 with the minimum bias trigger \(L_{\rm int}\) = 19.4 nb\).{-1}\) is the base for the measurement described in this thesis that is performed at central rapidity \(|y| < 0.9\) in the dielectron channel \(\jpsi\ \to e^+e^-\) . The fraction of non-prompt \jpsi\ is determined on a statistical basis down to \pt\ = 2 GeV/\).\). through the use of a maximum-likelihood fit procedure. The value of the non-prompt \jpsi\ fraction integrated over \pt\ is: \(f_{\rm b} (2 < \pt\ < 10 {\rm GeV}/c)\) = 0.103 \(\pm\) 0.022(stat) \(\pm\) 0.011 (syst). The non-prompt \jpsi\ fraction is further measured in four bins of transverse momentum and compared to similar measurements from other experiments. The non-prompt \jpsi\ fractions, both \pt-differential and \pt-integrated, are combined with the corresponding inclusive \jpsi\ cross-section measurements, providing prompt and non-prompt \jpsi\ cross-sections. The \pt-integrated cross section for prompt \jpsi\ is: \(\sigma_{\rm prompt \jpsi}(2 < \pt < 10~{\rm GeV}/c, |y| < 0.9) = 5.09~\pm~0.69~(\rm stat.) \pm 0.49 ~(\rm syst.)~{\rm \mu b}\). For non-prompt \jpsi\ the corresponding cross section is: \(\sigma_{\jpsi \leftarrow h_{\rm B}}(2 < \pt < 10~{\rm GeV}/c, |y| < 0.9)~ = ~ 0.58 ~\pm ~0.15~(\rm stat.) \pm ~0.08 (\rm syst.)~{\rm \mu b}\). Prompt and non-prompt \jpsi\ cross-section measurements are finally compared to several QCD-based models.