$SU(2)\times U(1)$ gauge invariance and the shape of new physics in rare $B$ decays

TL;DR

This paper explores how imposing full Standard-Model gauge invariance on new physics operators affects constraints derived from rare B decays, revealing new relationships between operators beyond standard assumptions.

Contribution

It introduces a framework enforcing full gauge invariance for new physics operators, leading to novel constraints in rare B decay analyses.

Findings

New gauge invariance constraints relate different new physics operators.

Enhanced bounds on new physics contributions from rare B decays.

Illustration with semi-leptonic B decay data.

Abstract

New physics effects in $B$ decays are routinely modeled through operators invariant under the strong and electromagnetic gauge symmetries. Assuming the scale for new physics is well above the electro-weak scale, we further require invariance under the full Standard-Model gauge symmetry group. Retaining up to dimension-6 operators, we unveil new constraints between different new-physics operators that are assumed to be independent in the standard phenomenological analyses. We illustrate this approach by analyzing the constraints on new physics from rare $B_{q}$ (semi-)leptonic decays.