Hunting New Animalcula with Rare K and B Decays

TL;DR

This paper reviews strategies for detecting new particles through rare K and B decays, emphasizing methods that bypass uncertain parameters and highlighting key decay channels with clean theoretical predictions.

Contribution

It introduces V_{cb}-independent ratios and V_{cb}-gamma plots, and identifies seven crucial decay modes for new physics searches with recent experimental data.

Findings

Updated V_{cb}-independent decay ratios.

Highlighted seven key decay channels for new physics.

Summarized recent experimental measurements of rare decays.

Abstract

We summarize the recent strategy for an efficient hunting of new animalcula with the help of rare K and B decays that avoids the use of the $V_{cb}$ and $V_{ub}$ parameters that are subject to tensions between their determinations from inclusive and exclusive decays. In particular we update the values of the $V_{cb}$-independent ratios of various K and B decay branching ratios predicted by the Standard Model. We also stress the usefulness of the $V_{cb}-\gamma$ plots in the search for new physics. We select the magnificant seven among rare K and B decays that should play a leading role in the search for new physics due to their theoretical cleanness: $B^+\to K^+(K^*)\nu\bar\nu$ and $K^+\to\pi^+\nu\bar\nu$ measured recently by Belle II and NA62, respectively, $K_L\to\pi^0\nu\bar\nu$ investigated by KOTO and also $B_{s,d}\to\mu^+\mu^-$ and $K_S\to\mu^+\mu^-$ measured by the LHCb, CMS and ATLAS experiments at CERN. %