Neutral $B$ mixing from 2+1 flavor lattice-QCD: the Standard Model and beyond

TL;DR

This paper presents a lattice-QCD calculation of B meson mixing matrix elements, including Standard Model and beyond contributions, with competitive errors and the first unquenched BSM results in a decade.

Contribution

It provides the first unquenched lattice-QCD calculation of B meson mixing matrix elements for beyond Standard Model operators in ten years.

Findings

Errors are competitive with existing Standard Model results.

First unquenched BSM matrix element calculation in a decade.

Preliminary results for five four-quark operators are reported.

Abstract

We report on the status of our lattice-QCD calculation of the hadronic contribution to $B_d^0$ and $B^0_s$ mixing, with 2+1 flavors of dynamical sea quarks. Preliminary results for hadronic mixing matrix elements are given for a basis of five four-quark, dimension-six, $\Delta B=2$ mixing operators that spans the space of all possible hadronic mixing contributions in the Standard Model and beyond. At the intermediate stage of analysis reported on in this work, our errors are competitive with published Standard Model matrix element results. For beyond the Standard Model matrix elements, this is the first unquenched calculation and the first new lattice-QCD calculation in ten years.