Correlating $B_q^0 \to \mu^+\mu^-$ and $K_L \to \pi^0\nu\bar\nu$ Decays with Four Generations

TL;DR

This paper explores how a hypothetical fourth generation of quarks could simultaneously affect rare B and K meson decays, providing potential correlations and signatures of new physics beyond the Standard Model.

Contribution

It demonstrates that the four-generation model can explain possible enhancements in rare decay rates and explores correlations among these processes as signatures of new physics.

Findings

Four-generation model can accommodate enhancements in $B_d^0 o \mu^+\mu^-$ and $K_L o \pi^0 uar u$ decays.

Potential correlations between new physics effects in B and K decay modes.

Current measurements are approaching sensitivities where these effects could be observed.

Abstract

The long-awaited $B_s\to \mu^+\mu^-$ mode has finally been observed at rate consistent with Standard Model, albeit lower by 1.2$\sigma$. There is some hint for New Physics in the rarer $B_d^0 \to \mu^+\mu^-$ decay, especially if the currently 2.2$\sigma$-enhanced central value persists with more data. The measurement of $CP$ violating phase $\phi_s$, via both $B_s\to J/\psi K\bar K$ and $J/\psi\pi\pi$ modes, has reached Standard Model sensitivity. These measurements stand major improvement when LHC enters Run 2. Concurrently, the $K_L\to\pi^0\nu\bar\nu$ and $K^+\to\pi^+\nu\bar\nu$ modes are being pursued in a similar time frame. We illustrate the possible correlations between New Physics effects in these four modes, using the fourth generation as example. While correlations may or may not exist in other New Physics models, the four generation model can accommodate enhancements in both $B_d^0 \to \mu^+\mu^-$ and $K_L\to\pi^0\nu\bar\nu$.