Light-cone Sum Rule Analysis of Semileptonic Decays $\Lambda_b^0 \to \Lambda_c^+ \ell^- \overline{\nu}_\ell$

Abstract

In this work, we analyze the semileptonic decay processes of $\Lambda_b \to \Lambda_c$ in the light-cone sum rule approach. In order to calculate the form factors of the $\Lambda_b$ baryon transition matrix element, we use the light-cone distribution amplitudes of $\Lambda_b$ obtained from the QCD sum rule in the heavy quark effective field theory framework. With the calculation of the six form factors of the $\Lambda_b \to \Lambda_c$ transition matrix element, the differential decay widths of $\Lambda_b^0 \to \Lambda_c^+ \ell^- \overline{\nu}_\ell (\ell = e, ~\mu, ~\tau)$ and their absolute branching fractions are obtained. Additionally, the ratio of $R(\Lambda_c^+) \equiv \mathcal{B}r(\Lambda_b^0 \to \Lambda_c^+ \tau^- \overline{\nu}_\tau)/\mathcal{B}r(\Lambda_b^0 \to \Lambda_c^+ \mu^- \overline{\nu}_\mu)$ is also obtained in this work. Our results are in accord with the newest experimental result and other theoretical calculations and predictions.