Searches for neutral Higgs bosons in extended models

Abstract

Searches for neutral Higgs bosons produced at LEP in association with Z bosons, in pairs and in the Yukawa process are presented in this paper. Higgs boson decays into b quarks, τ leptons, or other Higgs bosons are considered, giving rise to four-b, four-b+jets, six-b and four-τ final states, as well as mixed modes with b quarks and τ leptons. The whole mass domain kinematically accessible at LEP in these topologies is searched. The analysed data set covers both the LEP1 and LEP2 energy ranges and exploits most of the luminosity recorded by the DELPHI experiment. No convincing evidence for a signal is found, and results are presented in the form of mass-dependent upper bounds on coupling factors (in units of model-independent reference cross-sections) for all processes, allowing interpretation of the data in a large class of models.

A singlet extension of the MSSM with a dark matter portal

“…For masses below the upsilon threshold of ∼ 9.46 GeV, an analysis by [45] found that Υ → γA i imposes that C A i dd < 0.5 for tan β ∼ 1. Above this mass threshold the same analysis found the strongest constraint on the pseudoscalar mass coming from the process e + e − → bbA i → bbbb measured by DELPHI [44], setting the following limit, C A i dd < O (10). Additional constraints on light pseudoscalars arise form rare B and K decays such as: B → K + invisible, K → π + invisible, B → Ke + e − , K → πe + e − and K → π + + X as well as the muon g − 2 .…”

“…We analyze the parameter space of this model necessary to generate a SM-like Higgs boson with a mass of 126 GeV and light singlet-like states that are consistent with Higgs searches carried out by LEP [1,[42][43][44]. The SM-like Higgs mass is given by: …”

“…Constraints on light scalars also limit the parameter space of this model. In particular, searches by LEP [1,[42][43][44] place strong upper bounds on the two main scalar production mechanisms: e + e − → HZ and e + e − → HA, where H and A denote any of the CP-even or -odd scalars respectively. In the HZ channel these constraints assume that each scalar decays to bb or τ + τ − with a branching fraction equal to one.…”

“…The possibility of Higgs cascade decays has also been searched for at LEP [43,44]. They place strong bounds on two channels: (1) Associated Higgs production with a Z, e + e − → ZH i , H i → A j A j and (2) Scalar-pseudoscalar pair production, e + e − → H i A j .…”

The Higgs sector of the μνSSM and collider physics

“…Let us remember that searches for h → ΦΦ and Φ → bb (where Φ is a CP-odd or CP-even Higgs) by OPAL [23] and DELPHI [24] impose a strong constraint on the parameter space of the Standar Model. Once combined these analyses, one obtains M H > 110 GeV for ξ ∼ 1.…”