Sum rule estimate of the subleading non-perturbative contributions to B_s–B_s mixing

摘要

We use QCD sum rules to compute the matrix elements of the ΔB=2 operators appearing in the heavy-quark expansion of the width difference of the B s mass eigenstates. The main focus of our analysis is on the subleading operators R 2 and R 3, which appear at next-to-leading order in the 1/m b expansion. The matrix elements of these operators are already essential for precise phenomenology, but their calculation in lattice QCD is lacking and the values given here provide a first estimate of their values. We conclude that the violation of the factorization approximation for these matrix elements due to non-perturbative vacuum condensates is as low as 1–2%.