Quang-Chau Vo | Searcharxiv

arXiv2025

Polarization observables in semileptonic $V\to P$ decays of quarkonia

We investigate the weak semileptonic decays of the charmonium $J/ψ$ and bottomonium $Υ(1S)$ into a pseudoscalar meson, namely, the $J/ψ\to D_{(s)}\ell\barν_\ell$ and $Υ(1S)\to B_{(c)}\ell\barν_\ell$ decays. We focus on the polarization observables including the forward-backward asymmetry, final lepton polarization, and lepton-side convexity parameter. In order to define these quantities, we apply the helicity amplitude method and obtain a twofold angular decay distribution for a general $V\to P\ell\barν_\ell$ case. The hadronic form factors are taken from our previous work, where they were calculated in the Covariant Confined Quark Model. We provide theoretical predictions for the polarization observables and compare them with the literature.

hep-ph↗

arXiv2024

Radiative decays \$D^*_{(s)}\to D_{(s)}γ$ in covariant confined quark model

Radiative decays $D^*_{(s)}\to D_{(s)}γ$ are revisited in light of new experimental data from the \textit{BABAR} and BESIII collaborations. The radiative couplings $g_{D^*Dγ}$ encoding nonperturbative QCD effects are calculated in the framework of the covariant confined quark model developed by us. We compare our results with other theoretical studies and experimental data. The couplings (in $\textrm{GeV}^{-1}$) $|g_{D^{*+}D^+γ}| = 0.45(9)$ and $|g_{D^{*0}D^0γ}| = 1.72(34)$ calculated in our model agree with the corresponding experimental data $|g_{D^{*+}D^+γ}|=0.47(7)$ and $|g_{D^{*0}D^0γ}|=1.77(16)$. The most interesting case is the decay $D^*_s\to D_sγ$, for which a recent prediction based on light-cone sum rules at next-to-leading order $|g_{D^*_s D_sγ}|=0.60(19)$ deviates from the first (and only to date) lattice QCD result $|g_{D^*_s D_sγ}|=0.11(2)$ at nearly $3σ$. Our calculation yields $|g_{D^*_s D_sγ}|=0.29(6)$, which falls somehow between the two mentioned results, although it is larger than those predicted in other studies using quark models or QCD sum rules.

hep-ph↗