A new puzzle in non-leptonic B decays

TL;DR

This paper introduces new observables in non-leptonic B decays to reduce uncertainties and enhance sensitivity to New Physics, revealing deviations from the Standard Model that suggest possible NP contributions.

Contribution

It proposes optimized observables for B decays that minimize hadronic uncertainties and analyze their deviations to identify potential New Physics effects.

Findings

Deviations in branching ratio ratios suggest NP involving Wilson coefficients ${ m C}_4$, ${ m C}_6$, and ${ m C}_{8g}$.

Optimized observables show distinctive deviation patterns under NP scenarios.

NP effects could cause up to an order of magnitude difference in certain observables.

Abstract

We build a set of new observables using closely related non-leptonic penguin-mediated $B_d$ and $B_s$ 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 optimised observables are designed to reduce hadronic uncertainties, mainly coming from form factors and power-suppressed infrared divergences, and thus maximize their sensitivity to New Physics (NP). The deviations observed with respect to the SM in the ratios of branching ratios of ${\bar B}_{d,s}\to K^{*0}\bar{K}^{*0}$ ($2.6\sigma$) and ${\bar B}_{d,s}\to K^{0}\bar{K}^{0}$ ($2.4\sigma$) can be explained by simple NP scenarios involving the Wilson coefficients ${\cal C}_4$ and ${\cal C}_6$ (QCD penguin operators) and the coefficient ${\cal C}_{8g}$ (chromomagnetic operator). The optimised observables for ${\bar B}_{d,s}\to K^{0}\bar{K}^{*0}$ and ${\bar B}_{d,s}\to\bar{K}^{0}{K^{*0}}$ show distinctive patterns of deviations with respect to their SM predictions under these NP scenarios. The pattern of deviations of individual branching ratios, though affected by significant hadronic uncertainties, suggests that NP is needed both in $b\to d$ and $b\to s$ transitions. We provide the regions for the Wilson coefficients consistent with both optimised observables and individual branching ratios. The NP scenarios considered to explain the deviations of ${\bar B}_{d,s}\to K^{*0}\bar{K}^{*0}$ and ${\bar B}_{d,s}\to K^{0}\bar{K}^{0}$ can yield deviations up to an order of magnitude among the observables that we introduced for ${\bar B}_{d,s} \to K^{0} \bar{K}^{*0}$ and ${\bar B}_{d,s}\to\bar{K}^{0} {K^{*0}}$. Probing these new observables experimentally may confirm the consistency of the deviations already observed and provide a highly valuable hint of NP in the non-leptonic sector.