Eur. Phys. J. C (2024) 84: 1308
https://doi.org/10.1140/epjc/s10052-024-13622-8

Regular Article - Theoretical Physics

Form factors of ${\Lambda }_b^0\to {\Lambda }_c{(2595)}^{+}$ within light-cone QCD sum rules

¹ Institute of Particle and Nuclear Physics, Henan Normal University, 453007, Xinxiang, Henan, People’s Republic of China
² Department of Physics, National University of Defense Technology, 410073, Changsha, Hunan, People’s Republic of China

^a duanhuihui@htu.edu.cn

Received: 2 August 2024
Accepted: 17 November 2024
Published online: 21 December 2024

Abstract

In this work, we calculated the form factors of the weak decay process ${\Lambda }_b^0\to {\Lambda }_c{(2595)}^{+}$, where the final charm baryon represents an excited state with spin-parity ${\frac{1}{2}}^{-}$. Utilizing the light-cone QCD sum rules approach, we incorporated the contributions of the lowest two charm baryon states: the ground state ${\Lambda }_c$ with $J^P={\frac{1}{2}}^{+}$ and the excited state ${\Lambda }_c{(2595)}^{+}$ with $J^P={\frac{1}{2}}^{-}$ in the hadronic representation of the ${\Lambda }_b\to {\Lambda }_c{(2595)}^{+}$ transition correlation function. This approach allows us to extract the form factors of the ${\Lambda }_b^0\to {\Lambda }_c{(2595)}^{+}$ from ${\Lambda }_b^0\to {\Lambda }_c^{+}$ transition. During the light-cone QCD sum rules procedure, we employed the light-cone distribution amplitudes (LCDAs) of the ${\Lambda }_b$ baryon. Furthermore, by combining these form factors with the helicity amplitudes of the bottom baryon transition matrix elements, we calculated the differential decay widths for the processes ${\Lambda }_b^0\to {\Lambda }_c{(2595)}^{+}{\ell }^{-}{\overline{\nu }}_{\ell }$ and provided the optimal choice of the interpolating current for ${\Lambda }_c$ in this process. Additionally, within the lifetime of ${\Lambda }_b^0$, we obtained the absolute branching fractions for the semileptonic decays ${\Lambda }_b^0\to {\Lambda }_c{(2595)}^{+}{\ell }^{-}{\overline{\nu }}_{\ell }$. With the branching fractions of ${\Lambda }_b^0\to {\Lambda }_c{(2595)}^{+}{\ell }^{-}{\overline{\nu }}_{\ell }$ calculated in this work, we also determined the parameter $\mathcal{R}({\Lambda }_c{(2595)}^{+})$ which tests the lepton flavor universality. This parameter is defined as the ratio of branching fractions $\mathcal{B}r({\Lambda }_b^0\to {\Lambda }_c{(2595)}^{+}{\tau }^{-}{\overline{\nu }}_{\tau })$ and $\mathcal{B}r({\Lambda }_b^0\to {\Lambda }_c{(2595)}^{+}{\mu }^{-}{\overline{\nu }}_{\mu })$. Our results provide a valuable theoretical test for these decay channels and offer insights into the LCDAs of bottom baryons, paving the way for further in-depth investigations.