IFIC Seminar: Status of lepton universality within and beyond the Standard model

by Nejc Kosnik (University of Ljubljana)

Tuesday 7 May 2024, 12:00 → 13:00 Europe/Madrid

1001-Primera-1-1-1 - Paterna. Seminario (Universe)

We describe the current experimental status of the lepton flavour universality. We focus on the long-standing discrepancy in lepton flavor universality ratios R_D and R_{D^{*}} and assess the status of scalar leptoquark states R_2, R~_2 and S1 which can in principle provide a desired enhancement of $\mathcal{B}(B\to D^{(* )}\tau \nu)$ in a minimal setup with two Yukawa couplings only.

We consider unavoidable low-energy constraints, Z-pole measurements as well as high-p_T constraints. After setting mass of each leptoquark to 1.5 TeV we find that of all considered states only S1 leptoquark, coupled to both chiralities of leptons and quarks, is still a completely viable solution while the scenario with R_2 is in serious tension with the di-tau production LHC constraints at high-p_T and with $\Gamma(Z \to \tau \tau)$. We comment on the future experimental tests of S1 scenario.