Form factors of $Λ_b^0 \to Λ_c(2595)^+$ within light-cone QCD sum rules

Abstract

In this work, we calculated the form factors of the weak decay process $Λ_b^0 \to Λ_c(2595)^+$, 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 $Λ_c$ with $J^P=\frac{1}{2}^+$ and the excited state $Λ_c(2595)^+$ with $J^P=\frac{1}{2}^-$ in the hadronic representation of the $Λ_b \to Λ_c(2595)^+$ transition correlation function. This approach allows us to extract the form factors of the $Λ_b^0 \to Λ_c(2595)^+$ from $Λ_b^0 \to Λ_c^+$ transition. During the light-cone QCD sum rules procedure, we employed the light-cone distribution amplitudes (LCDAs) of the $Λ_b$ 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 $Λ_b^0 \to Λ_c(2595)^+\ell^-\barν_\ell$ and provided the optimal choice of the interpolating current for $Λ_c$ in this process. Additionally, within the lifetime of $Λ_b^0$, we obtained the absolute branching fractions for the semileptonic decays $Λ_b^0 \to Λ_c(2595)^+ \ell^- \barν_\ell$. With the branching fractions of $Λ_b^0 \to Λ_c(2595)^+ \ell^- \barν_\ell$ calculated in this work, we also determined the parameter $R(Λ_c(2595)^+)$ which tests the lepton flavor universality. This parameter is defined as the ratio of branching fractions $Br(Λ_b^0 \to Λ_c(2595)^+τ^-\barν_τ)$ and $Br(Λ_b^0 \to Λ_c(2595)^+μ^-\barν_μ)$. 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.