Search for tau lepton flavour violating decays at Belle II

Stage numéro : M2-1920-BE-01
Laboratoire :Centre de Physique des Particules de Marseille Case 902
 163 avenue de Luminy - 13288 Marseille Cedex 9
Directeur :Cristinel Diaconu - 04.91.82.72.01 - diaconu@cppm.in2p3.fr
Correspondant :William Gillard - 04.91.82.72.67 - gillard@cppm.in2p3.fr
Groupe d'accueil :Belle II
Chef de groupe :Justine Serrano - 04.91.82.72.80 - serrano@cppm.in2p3.fr
Responsable de stage :Justine Serrano - 0033 4 91 82 72 80 - serrano@cppm.in2p3.fr

Thématique : Physique des particules

Being forbidden in the Standard Model (SM) of particle physics, lepton flavor violating decays are among the most powerful probes to search for physics beyond the SM. In view of the recent anomalies seen by LHCb on tests of lepton flavor universality, the interest of tau lepton flavor violating decays has been greatly reinforced. In particular, several new physics models predict branching fractions of τ→ μμμ and tau → μγ just below the current experimental limits.

The Belle II experiment located at KEK, Japan, has just started physics data taking, aiming at collecting 50 times more data than its predecessor, Belle, by 2027. Thanks to its clean environment and high ττ cross section, it provides an ideal environment to study tau decays. The goal of this internship is to perform a sensitivity study of the tau → μμμ decay using the simulated data.

The analysis code is based on ROOT and python. Multivariate methods will be studied to optiimze the analysis performances.