On the $D^*_s$ and charmonia leptonic decays

TL;DR

This paper reports on lattice QCD calculations of decay constants for various mesons to help constrain extended Higgs sector models, motivated by recent flavor physics anomalies and the need for precise hadronic parameters.

Contribution

First lattice QCD determination of decay constants for $D^*_s$, $ ext{eta}_c$, $ ext{eta}_c(2S)$, $J/ ext{psi}$, and $ ext{psi}(2S)$ using ${ m N_f}=2$ Wilson-Clover fermions to inform extended Higgs sector constraints.

Findings

Decay constants extracted with controlled systematic errors.

Results span multiple lattice spacings and pion masses for reliable extrapolation.

Provides essential hadronic inputs for new physics phenomenology.

Abstract

Among the different scenarios of New Physics, those with an extended Higgs sector are examined with a lot of attention. Recent experimental observations of several anomalies in flavour physics with respect to expectations of the Standard Model further motivate the effort of phenomenologists. First, informations about the $R_{D_s}$ ratio, a test of lepton flavour universality equivalent to $R_D$, already measured, but with the $s$ quark as spectator, are awaited in coming years to constrain the corner of an extended Higgs sector with charged doublets. On another side, leptonic widths of pseudoscalar quarkonia are particularly interesting to test an extended Higgs sector with a light CP-odd Higgs boson singlet, through the study of its mixing with quarkonia states. Hadronic parameters entering those processes have to be determined from lattice QCD with enough confidence on the control of systematic errors. We report on the very first step of a long-term program tackled with ${\rm N_f}=2$ Wilson-Clover fermions to put relevant constraints on extensions of the Higgs sector: extraction of decay constants of $D^*_s$, $\eta_c$, $\eta_c(2S)$, $J/\psi$ and $\psi(2S)$ with lattice ensembles provided by the CLS effort, considering 2 lattice spacings and a large range of pion masses to estimate cut-off effects and extrapolate results to the chiral limit.