A light NMSSM pseudoscalar Higgs boson at the LHC redux

TL;DR

This paper investigates the potential for discovering a light pseudoscalar Higgs boson in the NMSSM at the LHC, focusing on production channels and decay signatures that could distinguish it from minimal models.

Contribution

It identifies promising decay channels of heavier scalar Higgs bosons into pseudoscalars and provides benchmark points for experimental searches at the LHC.

Findings

Decays of heavier scalars into pseudoscalars are promising discovery channels.

The $bar{b}$-associated production of the pseudoscalar is less promising after Higgs mass measurements.

Benchmark points for pseudoscalar detection via scalar decays are proposed.

Abstract

The Next-to-Minimal Supersymmetric Standard Model (NMSSM) contains a singlet-like pseudoscalar Higgs boson in addition to the doublet-like pseudoscalar of the Minimal Supersymmetric Standard Model. This new pseudoscalar can have a very low mass without violating the LEP exclusion constraints and it can potentially provide a hallmark signature of non-minimal supersymmetry at the LHC. In this analysis we revisit the light pseudoscalar in the NMSSM with partial universality at some high unification scale. We delineate the regions of the model's parameter space that are consistent with the up-to-date theoretical and experimental constraints, from both Higgs boson searches and elsewhere (most notably $b$-physics), and examine to what extent they can be probed by the LHC. To this end we review the most important production channels of such a Higgs state and assess the scope of its observation at the forthcoming Run-2 of the LHC. We conclude that the $b\bar{b}$-associated production of the pseudoscalar, which has been emphasised in previous studies, does not carry much promise anymore, given the measured mass of the Higgs boson at the LHC. However, the decays of one of the heavier scalar Higgsbosons of the NMSSM can potentially lead to the discovery of its light pseudoscalar. Especially promising are the decays of one or both of the two lightest scalar states into a pseudoscalar pair and of the heaviest scalar into a pseudoscalar and a $Z$ boson. Since the latter channel has not been explored in detail in the literature so far, we provide details of some benchmark points which can be probed for establishing its signature.