Subleading Isgur-Wise Function of Λ_btoΛ_(c1) using QCD sum rules

Subleading Isgur-Wise form factor $\tau(v\cdot v')$ at ${\cal O}(1/m_Q)$ for $\Lambda_b\to\Lambda_{c1}^{1/2,3/2}$ weak transition is calculated by using the QCD sum rules in the framework of the heavy quark effective theory (HQET), where $\Lambda^{1/2}_{c1}$ and $\Lambda^{3/2}_{c1}$ 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 $\Lambda^{1/2}_{c1}$ and $\Lambda^{3/2}_{c1}$ in the analysis. The slope parameter $\rho^2$ in linear approximation of $\tau$ is obtained to be $\rho^2=2.76$ and the interception to be $\tau(1)=-1.27$ GeV.