Within the framework of covariant confined quark model, we compute the transition form factors of D and D s mesons decaying to light scalar mesons f 0 ð980Þ and a 0 ð980Þ. The transition form factors are then utilized to compute the semileptonic branching fractions. We study the channels, namely, D þ ðsÞ → f 0 ð980Þl þ ν l and D → a 0 ð980Þl þ ν l for l ¼ e and μ. For computation of semileptonic branching fractions, we consider the a 0 ð980Þ meson to be the conventional quark-antiquark structure and the f 0 ð980Þ meson as the admixture of ss and light quark-antiquark pairs. Our findings are found to support the recent BESIII data.

Here, we study the B s → D ( * ) s ℓν ℓ semileptonic decays within the Standard Model framework of covariant confined quark model. The necessary transition form factors are computed in the entire dynamical range of momentum transfer squared with built-in infrared confinement. Our computed ratios of the decay widths from tau mode to muon mode for D s and D * s mesons are found to be R(D s ) = 0.271 ± 0.069 and R(D * s ) = 0.240 ± 0.038. We further determine the ratio of the decay width from D s and D * s channel for muon mode Γ(B s → D s µ + ν µ )/Γ(B s → D * s µ + ν µ ) = 0.451±0.093. Our results are in excellent agreement with the data from recent LHCb experiments as well as lattice quantum chromodynamics simulations. We have also compared the shape of differential decay distribution for B s → D * s µ + ν µ with the recent LHCb data and our results are in very good agreement throughout all the individual bins. Some other physical observables such as forwardbackward asymmetry and longitudinal polarizations of leptons in the final state are also computed.

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Within the framework of nonrelativistic quark-antiquark Cornell potential model formalism, we study the annihilation of heavy quarkonia. We determine their annihilation widths resulting into γγ, gg, 3γ, 3g and γgg and compare our findings with the available theoretical results and experimental data. We also provide the charge radii and absolute square of radial Schrödinger wave function at zero quark-antiquark separation.