The purely leptonic and semileptonic decays of $D^{*}_{s}$ meson

TL;DR

This work addresses the weak decays of the vector charm-strange meson $D^{*}_{s}$ within the Standard Model, focusing on CKM-favored leptonic decays $D^{*}_{s}\to \ell\bar{\nu}_{\ell}$ and semileptonic decays $D^{*}_{s}\to M\ell\bar{\nu}_{\ell}$ with $M=\phi,\eta^{(\prime)}$. It adopts a self-consistent covariant light-front (CLF) approach to compute decay constants and the $D^{*}_{s}\to M$ transition form factors, constructs helicity amplitudes, and derives differential decay rates and angular observables, including lepton-spin asymmetries $A^{M}_{\lambda}(q^2)$ and forward-backward asymmetries $A^{M}_{\theta}(q^2)$. The study yields $\Gamma^{D^{*}_{s}}_{\rm tot}\approx0.131$ keV and branching fractions $\mathcal{B}(D^{*}_{s}\to \ell\bar{\nu}_{\ell})={\cal O}(10^{-5})$ and $\mathcal{B}(D^{*}_{s}\to M\ell\bar{\nu}_{\ell})={\cal O}(10^{-7})$, with semileptonic modes offering viable prospects for observation at future facilities. The results—matched to BESIII measurements for the leptonic channel and complemented by detailed $q^2$-dependent distributions and asymmetries—provide precise SM benchmarks to test axial-vector interactions and search for lepton-flavor universality violations in charm. These predictions will guide upcoming experiments at Belle II, STCF, and LHCb in probing rare charm decays and potential new physics.

Abstract

With the potential prospects of the $D^{*}_{s}$ at high-luminosity heavy-flavor experiments in the future, we investigated the CKM-favored and tree-dominated leptonic $D^{*}_{s}\to\ell\barν_{\ell}$ and semileptonic $D^{*}_{s}\to M\ell\barν_{\ell}$ ($M=φ, η^{(\prime)}$ and $\ell=e, μ$) weak decays in the Standard Model (SM). The theoretical predictions and some discussions for the observable quantities including the total width of $D^{*}_{s}$ mesons, the branching fractions of leptonic $D^{*}_{s}\to\ell\barν_{\ell}$ and semileptonic $D^{*}_{s}\to M\ell\barν_{\ell}$ weak decays, the lepton spin asymmetry and forward-backward asymmetry are presented. Numerically, the weak decays of $D^{*}_{s}\to\ell\barν_{\ell}$ and $D^{*}_{s} \to M\ell\barν_{\ell}$ have relatively large branching fractions of the order $\mathcal{O}(10^{-5})$ and $\mathcal{O}(10^{-7})$ respectively, which are expected to be observed in future experiments.

Figures (3)

• Figure 1: The $q^{2}$-dependences of form factors for $D^{*}_{s}\to \phi$ and $D^{*}_{s}\to \eta_{s}$ transitions.
• Figure 2: The $q^{2}$-dependences of differential decay rates ${\rm d} \Gamma/{\rm d} q^{2}$.
• Figure 3: The $q^{2}$-dependences of $A^{\phi,\eta^{(\prime)}}_{\theta}$ and $A^{\phi,\eta^{(\prime)}}_{\lambda}$.