On the $b-$ Quark Kinetic Energy in the $\Lambda_b$

Abstract

We consider the problem of determining the matrix element of the heavy quark kinetic energy operator between $\Lambda_b$ baryonic states by three point function QCD sum rules in the Heavy Quark Effective Theory. We discuss the main features and the uncertainties associated to such an approach. Numerically, we find the result: ${\langle{\cal K}\rangle}_{\Lambda_b} = - (0.6 \pm 0.1) \; GeV^2$. Within the uncertainty of the method, such result indicates a value of the heavy quark kinetic energy in the baryon similar in size to that in the meson.