Reduced branching ratio for H -> AA -> 4 tau from A - eta_b mixing

TL;DR

This paper demonstrates that A - eta_b mixing significantly reduces the branching ratio of H -> AA -> 4 tau in models with extended Higgs sectors, allowing lighter Higgs bosons to evade experimental bounds.

Contribution

It reveals that A - eta_b mixing suppresses the H -> AA -> 4 tau decay mode in a specific mass range, relaxing previous experimental constraints on light Higgs bosons.

Findings

A - eta_b mixing reduces the H -> AA -> 4 tau branching ratio for M_A between 9 and 10.5 GeV.

This mixing resolves tension between eta_b(1S) mass measurements and QCD predictions.

The suppression is largely independent of A's coupling to b quarks.

Abstract

Models with an extended Higgs sector, as the NMSSM, allow for scenarios where the Standard Model-like CP-even Higgs boson H decays dominantly as H -> AA -> 4 tau where A is a light CP-odd Higgs boson. Tight constraints on this scenario in the form of lower bounds on M_H have recently been published by the ALEPH group. We show that, due to A - eta_b mixing, the branching ratio H -> AA -> 4 tau is strongly reduced for M_A in the range 9 - 10.5 GeV. This is the range of M_A in which the tension between the observed eta_b(1S) mass and its prediction based on QCD can be resolved due to mixing, and which is thus still consistent with a light CP-even Higgs boson H satisfying LEP constraints with a mass well below 114 GeV. This result is practically independent from the coupling of A to b quarks.