NNLO QCD corrections to $B$-meson mixing

TL;DR

This paper presents the calculation of NNLO QCD corrections to the width difference in neutral B-meson mixing, significantly reducing theoretical uncertainties and aligning predictions with experimental data.

Contribution

It provides the first complete NNLO QCD correction calculation for $ ext{Δ} ext{Γ}_s$ in B-meson mixing, addressing previous perturbative errors.

Findings

Reduction of theoretical uncertainties in $ ext{Δ} ext{Γ}_s$

Enhanced agreement between theory and experiment

New computational techniques for evanescent operators

Abstract

We report on the calculation of next-to-next-to-leading order (NNLO) QCD corrections to the width difference $\Delta \Gamma_s$ in the neutral $B$-meson mixing process $B^0_s - \bar{B}^0_s$. These contributions represent an important step in the task of reducing the existing large perturbative errors in the theory prediction for $\Delta \Gamma_s$ and approaching the current experimental uncertainties. We explain the theoretical framework employed in this computation and point out important subtleties in the treatment of evanescent operators and the renormalization. Part of our new results is already available in the literature, while the remaining pieces are expected to be published later this year.