Semileptonic Decays of Heavy Vector Mesons in Hard-Wall AdS/QCD with $N_{f}=5$
We present a systematic study of semileptonic decays of heavy vector mesons within the Hard-Wall AdS/QCD framework. Semileptonic decays provide a clean environment for testing the Standard Model because the leptonic current is well understood, while the hadronic part is encoded in transition form factors that reflect non-perturbative QCD dynamics. The processes under consideration include: \( ψ\to D^{*-} ( D^{-} ) \ell^{+} ν_{\ell} \), \( D^{*0} \to π^{-} \ell^{+} ν_{\ell} \), \( D^{*+}_{s} \to K^{0} \ell^{+} ν_{\ell} \), \( D^{*0} \to ρ^{-} \ell^{+} ν_{\ell} \), \( B_c^{*+} \to B^{*0} \ell^{+} ν_{\ell} \), \( B_c^{*+} \to ψ\,\ell^{+} ν_{\ell} \), \( B^{*-} \to D^{*0} \ell^{-} \barν_{\ell} \), \( B^{*0} \to D^{*+}(D^{+}) \ell^{-} \barν_{\ell} \), \( B^{*0}_{s} \to D^{*+}_{s} (D^{+}_{s}) \ell^{-} \barν_{\ell} \), \( ψ\to D^{*-}_{s}(D^{-}_{s}) \ell^{+} ν_{\ell} \), \( D^{*0} \to K^{*-} (K^{-}) \ell^{+} ν_{\ell} \), \( B_c^{*-} \to D^{*0} \ell^{-} \barν_{\ell} \), \( \bar{B_{s}}^{*0} \to K^{*+} \ell^{-} \barν_{\ell} \), and \( \bar{B}^{*0} \to ρ^{+} \ell^{-} \barν_{\ell} \). These decays correspond to four different quark-level transitions: \(c\to d\), \(b\to c\), \(c\to s\), and \(b\to u\), allowing us to explore a broad range of flavor dynamics.\\ Using the Hard-Wall AdS/QCD model, we compute the relevant transition form factors as functions of the momentum transfer \(q^{2}\). The framework provides analytic expressions for meson wave functions and decay constants, which serve as inputs for the form-factor calculations. From these form factors, we evaluate the differential and integrated branching ratios for each decay mode. Where possible, we compare our predictions with results obtained from other non-perturbative approaches.