Flavor violating leptonic decays of the Higgs boson

TL;DR

This paper investigates flavor-violating leptonic decays of the Higgs boson within an MSSM extension, finding that a substantial branching ratio for $H^0_1 o \mu au$ is possible, consistent with experimental hints and potentially indicating new physics.

Contribution

It introduces a model with a vectorlike leptonic generation to explain flavor-violating Higgs decays, including detailed calculations of decay rates and CP phase effects.

Findings

Branching ratio for $H^0_1 o \mu au$ can reach about 1%.

Flavor-violating decays are consistent with current experimental limits.

Dependence of decay rates on CP phases is analyzed.

Abstract

Recent data from the ATLAS and CMS detectors at the Large Hadron Collider at CERN give a hint of possible violation of flavor in the leptonic decays of the Higgs boson. In this work we analyze the flavor violating leptonic decays $H^0_1\to l_i \bar l_j$ ($i\neq j$) within the framework of an MSSM extension with a vectorlike leptonic generation. Specifically we focus on the decay mode $H^0_1\to \mu\tau$. The analysis is done including tree and loop contributions involving exchange of $W, Z$, charge and neutral higgs and leptons and mirror leptons, charginos and neutralinos and sleptons and mirror sleptons. It is found that a substantial branching ratio of $H^0_1\to \mu\tau$, i.e., of as much a ${\cal{O}}(1)\%$, can be achieved in this model, the size hinted by the ATLAS and CMS data. The flavor violating decays $H^0_1\to e\mu, e\tau$ are also analyzed and found to be consistent with the current experimental limits. An analysis of the dependence of flavor violating decays on CP phases is given. The analysis is extended to include flavor decays of the heavier Higgs bosons. A confirmation of the flavor violation in Higgs boson decays with more data that is expected from LHC at $\sqrt s=13$ TeV will be evidence of new physics beyond the standard model.