${\Lambda }_b\to {\Lambda }_c$ Form Factors from QCD Light-Cone Sum Rules

Abstract

In this work, we calculate the transition form factors of ${\Lambda }_b$ decaying into ${\Lambda }_c$ within the framework of light-cone sum rules with the distribution amplitudes (DAs) of ${\Lambda }_b$-baryon. In the hadronic representation of the correlation function, we have isolated both the ${\Lambda }_c$ and the ${\Lambda }_c^{\ast }$ states so that the ${\Lambda }_b\to {\Lambda }_c$ 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 ${\Lambda }_b$ in the numerical calculation. We present the numerical predictions on the ${\Lambda }_b\to {\Lambda }_c$ form factors and the branching fractions, the averaged forward-backward asymmetry , the averaged final hadron polarization and the averaged lepton polarization of the ${\Lambda }_b\to {\Lambda }_c\ell \mu$ decays, as well as the ratio of branching ratios $R_{{\Lambda }_c}$, and the predicted $R_{{\Lambda }_c}$ can be consistent with the LHCb data.

Comments: 22 pages, 2figure