First quenched results for the matrix elements of the B_{B_s} mixing parameter in the static limit from tmQCD

TL;DR

This paper presents the first quenched lattice QCD results for the B_{B_s} mixing parameter using static approximation for the heavy quark and twisted mass fermions for the strange quark, including non-perturbative renormalization.

Contribution

It introduces a novel lattice QCD approach combining static heavy quark treatment with twisted mass fermions for the strange quark to compute B_{B_s} mixing parameters.

Findings

Observed suppression of excited state contributions.

Provided preliminary non-perturbative renormalization factors.

Reported initial matrix element results for B_s-meson mixing.

Abstract

We report on a non-perturbative study of the scale-dependent renormalization factors of a multiplicatively renormalizable basis of Delta B=2 parity-odd four-fermion operators in quenched lattice QCD. We also present some preliminary results of the matrix elements related to the mixing parameter of the B_s-meson. In our lattice formulation, the heavy quark is treated in the static approximation, while the strange one belongs to a doublet of twisted mass fermions at full twist, i.e. with twist angle alpha=pi/2. In this framework, the parity-even Delta B=2 four-fermion operators responsible for the mixing are rotated onto a linear combination of parity-odd operators in the above-mentioned basis. Their physical matrix elements between static B_s-mesons are extracted from lattice correlators with Schroedinger functional boundary conditions. We observe a suppression of excited state contributions to the B_{B_s} mixing parameter and speculate about possible explanations.