$B_{s}^0\to K^0\overline{K}{}^0$ beyond the Standard Model

TL;DR

This paper investigates the rare decay $B_s^0 o K^0ar{K}^0$ beyond the Standard Model, analyzing potential new physics explanations for observed deviations and emphasizing the role of flavor symmetry relations.

Contribution

It systematically examines new physics scenarios explaining deviations in $B_s$ decay relations, finding most solutions highly fine-tuned or inconsistent with other data.

Findings

Standard Model relations are violated at about 3σ.

Possible new physics explanations are highly fine-tuned or implausible.

The correlation between $B_s o Kar{K}$ and $B o ext{pi}K$ decays is crucial in the analysis.

Abstract

Within the Standard Model, the branching fraction of the rare decay $B_s\to K^0\bar K^0$ is related to other decay rates and CP asymmetries through the approximate $SU(3)$ flavor symmetry of the strong interactions and the heavy-quark limit. Three such relations were shown to be violated at a level of about $3\sigma$ each. By means of a systematic search for new-physics explanations of these puzzles, we find that possible solutions are highly fine-tuned and either excluded by other data or rather implausible. The tight correlation between $B_s\to K\bar K$ and $B\to\pi K$ decays, which is maintained even in the presence of flavor-specific new-physics operators, plays a central role in our analysis.