The 30 GeV Dimuon Excess at ALEPH

Abstract

A simple variation of a two-Higgs-doublet model is proposed to describe the $30\,{\rm GeV}$ dimuon excess reported by Heister in his reanalysis of $Z \to \bar bb$ events in ALEPH data taken in 1992-95. The heavier CP-even Higgs $H$ is the $125\,{\rm GeV}$ Higgs boson discovered at the LHC. The model admits two options for describing the dimuon excess: (1) The lighter CP-even Higgs $h$ and the CP-odd state $\eta_A$ are approximately degenerate and contribute to the $30\,{\rm GeV}$ excess. (2) Only the $h$ is at $30\,{\rm GeV}$ while the $\eta_A$ and $H$ are approximately degenerate at $125\,{\rm GeV}$. The ALEPH data favor option 1. Testable predictions are presented for LHC as well as LEP experiments. A potential no-go theorem for models of this type is also discussed.