Enhanced Bd --> mu+ mu- Decay: What if?

TL;DR

This paper explores the implications of an enhanced $B_d^0 o \mu^+\mu^-$ decay rate, suggesting it could indicate new physics like a fourth-generation quark and impact our understanding of the Higgs boson.

Contribution

It proposes that an observed enhancement in the rare decay could reveal evidence for a fourth-generation quark and challenge the current Higgs boson interpretation.

Findings

Enhanced decay rate could be detectable with existing LHC data.

Discovery would suggest new physics beyond the Standard Model.

Future measurements could probe even lower decay rates.

Abstract

If the very rare $B_d^0 \to \mu^+\mu^-$ decay is enhanced to (3--4) $\times 10^{-10}$ level or higher, it can be discovered with existing 2011-2012 LHC data. It might then cast some doubt on the Higgs boson nature of the 126 GeV boson, since the likely explanation would be due to the fourth generation $t^\prime$ quark. There is a mild motivation from the known tension in $\sin2\beta/\phi_1$. If discovery is made before the 13 TeV run, then the $b \to d$ quadrangle (modulo $m_{t'}$) would suddenly fall into our lap. Continued pursuit in future runs can probe below $3 \times 10^{-10}$.