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Utsab Dey

Publications and source records attributed to Utsab Dey.

3 recordsLinked to original sources
arXiv2026

Study of Form Factors and Observables in $B_c^- \rightarrow \bar{D}^{(*)0}\ell^-\barν_{\ell}$ and $B_c^- \rightarrow D^{(*)-}\ell^+\ell^-$ decays

We investigate the decays $B_c^- \rightarrow \bar{D}^{(*)0}\ell^-\barν_{\ell}$ and $B_c^- \rightarrow D^{(*)-}\ell^+\ell^-$ within the Standard Model (SM), employing perturbative QCD (pQCD) form factors that are sensitive to the wave functions of $B_c$ and $D^{(*)}$ mesons. Using lattice QCD inputs for $B \to D^{(*)}$ and $B_c \to D$ transitions, we extract the shape parameters of the meson wave functions and estimate the $q^2$-dependence of $B_c \to D^*$ form factors via heavy quark spin symmetry. We present predictions for branching fractions, lepton flavor violating observables, and perform a detailed angular analysis of the cascade decay $B_{c}^{-} \to D^{*-}(\to D^{0}π^{-}) \ell^+\ell^-$, providing SM expectations for several angular observables.

hep-ph↗
arXiv2026

Study of Form Factors and Observables in $B_c^- \rightarrow D_{s}^{*-}\ell^+\ell^-$ and $B_c^- \rightarrow D_{s}^{*-}ν\barν$ decays

We investigate the decays $B_c^- \rightarrow D_{s}^{(*)-}\ell^+\ell^-$ and $B_c^- \rightarrow D_{s}^{(*)-}ν\barν$ within the Standard Model (SM), employing perturbative QCD form factors that are sensitive to the wave functions of $B_c$ and $D_{s}^{(*)}$ mesons. We determine the shape parameters of these mesons and the $B_c \to D_s^{(*)}$ form factors at $q^2 = 0$ from available lattice QCD inputs for $B_s \to D_s^{(*)}$ and $B_c \to D_s$ transitions. To obtain the $q^2$ dependence of the $B_c \to D_s^*$ form factors, we employ heavy-quark spin symmetry and an appropriate parametrisation scheme over the allowed $q^2$ region. Based on these inputs, we present predictions for branching ratios and lepton-flavour-sensitive observables. Furthermore, we perform a detailed angular analysis of the cascade decay $B_c^- \to D_s^{*-}(\to D_s^- π^0)\,\ell^+\ell^-$, providing Standard Model predictions for several angular observables.

hep-ph↗
arXiv2025

Correlated study on some $B_{c}\rightarrow \text{ }P$ and $B_{c}\rightarrow\text{ }S$ wave channels in light of new inputs

This study investigates the decay modes of the $B_c$ meson, focusing on semileptonic and nonleptonic decay into S and P wave charmonia. The primary objective is to extract the shape parameter of the $B_{c}$ meson distribution amplitude through a data-driven approach, utilizing the lattice results on $B_{c}\rightarrowη_{c},J/ψ$ semileptonic form factors and yielding an estimate of ${ω_B}_c = 0.998(34)$ for the same. We use the form factors derived from the modified perturbative QCD framework in the analysis. This result and various other inputs on the radiative decays of the P wave charmonia enable us to estimate the $q^2$ shapes of the $B_{c}\rightarrowχ_{c0},χ_{c1}$ and $h_{c}$ form factors using pole expansion parametrization. Using these results, we have obtained predictions of LFUV observables $R(χ_{c0})=0.169(11)$, $R(χ_{c1})=0.126(2)$ and $R(h_{c})=0.113(3)$. Finally, we have presented predictions for branching ratios of some nonleptonic decay modes of the $B_{c}$ meson into S and P wave charmonia in the same modified perturbative QCD framework.

hep-ph↗