Leading Isgur-Wise form factor of $Λ_b\toΛ_{c1}$ transition using QCD sum rules

Abstract

The leading Isgur-Wise form factor $ξ(y)$ parametrizing the semileptonic transitions $Λ_b\toΛ^{1/2}_{c1}\ell\barν$ and $Λ_b\toΛ^{3/2}_{c1}\ell\barν$ is calculated by using the QCD sum rules in the framework of heavy quark effective theory, where $Λ^{1/2}_{c1}$ and $Λ^{3/2}_{c1}$ is the orbitally excited charmed baryon doublet with $J^P=(1^-/2,3^-/2)$. The interpolating currents with transverse covariant derivative are adopted for $Λ^{1/2}_{c1}$ and $Λ^{3/2}_{c1}$ in the analysis. The slope parameter $ρ^2$ in linear approximation of the Isgur-Wise function is obtained to be $ρ^2=2.01$, and the interception to be $ξ(1)=0.29$. The decay branching ratios are estimated.