Search for tau lepton flavour violating decays at Belle II

Stage numéro : Doctorat-1922-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
Directeur de thèse :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 in b → s and b → c processes, 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 τ→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 τ+ τ cross section, it provides an ideal environment to study tau decays. The goal of this phD is to analyze the first Belle II data in order to obtain the best experimental limits on the lepton flavor violating decays τ→lll, where l = e,μ. Additional decays such as τ→lγ or τ→lh, h being a hadronic system, could also be studied.

This phD will take place at CPPM, Marseille (https://www.cppm.in2p3.fr/web/en/index.html). Travels to KEK for collaboration meetings, and longer stay for participation to the data taking, are foreseen.

The funding of this phD is provided by an ERC grant obtained by Justine serrano.


Contract Period : 36 months


Expected date of employment : 1 October 2019


Remuneration : 2135 € monthly gross

Applicants must hold a Master degree (or equivalent) in Physics, or expect to hold such a degree by the start of employment.

Application including a CV, grade records, a motivation statement and contacts of three possible persons to supply letter of recommendation should be sent by June 21st to Justine Serrano serrano@cppm.in2p3.fr.

References:


https://arxiv.org/abs/1808.10567


https://hflav-eos.web.cern.ch/hflav-eos/tau/spring-2017/lfv-limits-plot.html


https://arxiv.org/abs/1903.11517


https://arxiv.org/pdf/1806.05689.pdf