Implication of possible observation of enhanced Bd0 --> mu+ mu- decay

TL;DR

This paper discusses the potential implications of observing an enhanced Bd0 --> mu+ mu- decay rate at the LHC, which could indicate new physics such as a fourth quark generation and challenge the identity of the 126 GeV boson.

Contribution

It explores the possibility that an enhanced decay rate could signal new physics beyond the Standard Model, including a fourth quark generation and non-Higgs nature of the 126 GeV boson.

Findings

Enhancement beyond 3-4 x 10^-10 suggests new physics.

Current data unlikely to detect below 3 x 10^-10.

Future runs at 13 TeV are crucial for observation.

Abstract

The very rare Bd0 --> mu+ mu- decay may be the last chance for New Physics in flavor sector at the LHC, before the 13 TeV run in 2015. Partially motivated by the known tension in sin(2beta/phi_1), enhancement beyond (3-4) x 10^-10 would likely imply the effect of a fourth generation of quarks. If observed at this level, the 126 GeV boson may not be the actual Higgs boson, while the b --> d quadrangle (modulo m_t') would jump out. The 2011-2012 data is likely not sensitive to values below 3 x 10^-10, and the mode should continue to be pursued with the 13 TeV run.