Hunting New Animalcula with Rare K and B 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. %