Shao-Qin Guo | Searcharxiv

arXiv2026

Semi-leptonic $B$ decays to tensor mesons

Using the form factors of the transtions $B\to T$ with $T$ refering to a tensor meson, such as $a_2(1320), f_2(1270),K^*_2(1430), D_2^*(2460)$ and $D^*_{2s}(2573)$, within the covariant light-front quark model (CLFQM), we provide a detailed investigation of the corresponding semi-leptonic decays $B\to T\ellν_\ell$ with $\ell=e,ν,τ$. All the branching ratios of these decays are larger than $10^{-5}$, in which the maximum value can reach up to $10^{-3}$, indicating promising prospects for experimental observation. Furthermore, we also calculate the longitudinal polarization fractions $f_L$ and forward-backward asymmetries $A_{FB}$ for these considered decays. All the decays $B\to T \ellν_{\ell}$ are dominated by the longitudinal polarization, where the polarization fractions can reach up to $\sim70\%$ for the decays $B\to T \ell^{\prime}ν_{\ell^\prime}$ with $\ell^\prime=e, μ$, those of the decays $B\to T τν_τ$ are a little smaller. The $A_{FB}$ values of the decays $B\to T \ell^{\prime}ν_{\ell^\prime}$ and $B\to T τν_τ$ have opposite signs.

hep-ph↗

arXiv2026

Systematic analysis of $D_{(s)}$ meson semi-leptonic decays in the covariant light-front quark model

The weak decays of the $D_{(s)}$ meson provide a pivotal platform to advance our understanding of the Standard Model (SM) and to explore New Physics (NP). In recent years, experiments have collected a significant amount of data on the $D_{(s)}$ meson decays, particularly from BESIII, which provides substantial support for theoretical research. In this work, we systematically investigate the semi-leptonic decays of $D_{(s)}$ meson to pseudoscalar (P), scalar (S), vector (V), and axial-vector (A) mesons within the framework of the covariant light-front quark model (CLFQM). We calculate the form factors of the transitions $D_{(s)}\to P,S,V,A$ and the branching ratios of the corresponding semi-leptonic decays, then compare them with experimental data and results from other theoretical models. The form factor values of the transitions $D_{(s)}\to P, V$ obtained from the CLFQM are consistent with those of other theoretical models and available data in most cases. However, significant discrepancies are found in some specific $D_{(s)}\to S,A$ transitions, such as $D\to a_0(980), a_0(1450)$ and $D_{(s)} \to K_{1B}$, compared to other theoretical calculations. The predicted branching ratios for the semi-leptonic decays $D\to P(V)\ellν_\ell$ with $\ell=e,μ$ agree well with experimental data and other theoretical results in most decay channels, validating the reliability of the model. However, for some $D\to S(V)\ellν_\ell$ decays, tension exists among different theoretical predictions and experimental results. Further clarification of such differences is necessary. Our study provides important insights into the internal structures for some scalar and axial-vector mesons and serves as a theoretical reference for future experiments.

hep-ph↗