Subleading Isgur-Wise Function of $Λ_b\toΛ_{c1}$ using QCD sum rules

Abstract

Subleading Isgur-Wise form factor $τ(v\cdot v')$ at ${\cal O}(1/m_Q)$ for $Λ_b\toΛ_{c1}^{1/2,3/2}$ weak transition is calculated by using the QCD sum rules in the framework of the heavy quark effective theory (HQET), where $Λ^{1/2}_{c1}$ and $Λ^{3/2}_{c1}$ are the orbitally excited charmed baryon doublet with $J^P=(1^-/2,3^-/2)$. We consider the subleading contributions from the weak current matching in the HQET. 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 $τ$ is obtained to be $ρ^2=2.76$ and the interception to be $τ(1)=-1.27$ GeV.