A new puzzle in non-leptonic B decays

TL;DR

This paper introduces new optimized observables for non-leptonic B decays that are less affected by theoretical uncertainties and finds potential signs of new physics in current experimental data, especially in $b o s$ and $b o d$ transitions.

Contribution

It proposes a set of optimized observables for penguin-mediated B decays that are cleaner than branching ratios and explores their potential to reveal new physics beyond the Standard Model.

Findings

Standard Model estimates are in ~2.5 sigma tension with experimental data.

Certain Wilson coefficients can explain the observed deviations.

Observables involving mixed states are particularly sensitive to new physics.

Abstract

We propose a set of new optimized observables using penguin mediated $\bar{B}_d$ and $\bar{B}_s$ decays: ${\bar B}_{d,s} \to K^{*0} \bar{K}^{*0}$, ${\bar B}_{d,s} \to K^{0} \bar{K}^{0}$, ${\bar B}_{d,s} \to K^{0} \bar{K}^{*0}$ and ${\bar B}_{d,s} \to \bar{K}^{0} {K^{*0}}$ together with their CP conjugate partners. These observables are substantially cleaner than the corresponding branching ratios, which are plagued by large end point divergences. We find that the dominant contribution to the uncertainties of these observables stem from the corresponding form factors. The Standard Model estimates for these observables corresponding to the $K^{*0}\bar{K}^{*0}$ and $K^0\bar{K}^0$ final states are in tension with their respective experimental numbers at the $\sim2.5 \sigma$ level. The pattern of deviations w.r.t these observables as well as the individual branching ratios suggest that a possible explanation might be new physics both in $b\to s$ and $b\to d$ transitions. We find that, taken one at a time, only the Wilson coefficients $C_{4d,s}^{NP}$ and $C_{8gd,s}^{NP}$ can potentially satisfy all the current experimental data on the branching ratios as well as the optimized observables. Furthermore, such observables involving mixed (pseudoscalar-vector) states like $K^{*0}\bar{K}^0$ etc show distinctive patterns sensitive to these different new physics explanations.