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

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 $3 \times 10^{-10}$.