$Λ_b \to Λ_c$ Form Factors from QCD Light-Cone Sum Rules

Abstract

In this work, we calculate the transition form factors of $Λ_b$ decaying into $Λ_c$ within the framework of light-cone sum rules with the distribution amplitudes (DAs) of $Λ_b$-baryon. In the hadronic representation of the correlation function, we have isolated both the $Λ_c$ and the $Λ_c^*$ states so that the $Λ_b \rightarrow Λ_c$ form factors can be obtained without ambiguity. We investigate the P-type and A-type current to interpolate the light baryons for a comparison since the interpolation current for the baryon state is not unique. We also employ three parametrization models for DAs of $Λ_b $ in the numerical calculation. We present the numerical predictions on the $Λ_b \rightarrow Λ_c$ form factors and the branching fractions, the averaged forward-backward asymmetry , the averaged final hadron polarization and the averaged lepton polarization of the $Λ_b \to Λ_c \ellμ$ decays, as well as the ratio of branching ratios $R_{Λ_c}$, and the predicted $R_{Λ_c}$ can be consistent with the LHCb data.