Probing the two light Higgs scenario in the NMSSM with a low-mass pseudoscalar

Abstract

In this article we propose a simultaneous collider search strategy for a pair of scalar bosons in the NMSSM through the decays of a very light pseudoscalar. The massive scalar has a mass around 126 GeV while the lighter one can have a mass in the vicinity of 98 GeV (thus explaining an apparent LEP excess) or be much lighter. The successive decay of this scalar pair into two light pseudoscalars, followed by leptonic pseudoscalar decays, produces clean multi-lepton final states with small or no missing energy. Furthermore, this analysis offers an alternate leptonic probe for the 126 GeV scalar that can be comparable with the ZZ * search channel. We emphasize that a dedicated experimental search for multi-lepton final states can be an useful probe for this scenario and, in general, for the NMSSM Higgs sector. We illustrate our analysis with two representative benchmark points and show how the LHC configuration with 8 TeV center-of-mass energy and 25 fb −1 of integrated luminosity can start testing this scenario, providing a good determination of the light pseudoscalar mass and a relatively good estimation of the lightest scalar mass. *

Collider signatures of a light NMSSM pseudoscalar in neutralino decays in the light of LHC results

“…This is particularly important in the regions of the parameter space with m h 0 1 < JHEP02(2014)048 These points are similar to those studied in a previous analysis [26] in the context of scalar Higgs decays h → a 0 1 a 0 1 . It should be noted that in order to obtain such a light a 0 1 the input parameters have to be carefully tuned.…”

“…This is favoured by the LHC observation of a Higgs boson with a mass in the 2 σ range 124 − 126.8 GeV (124.5 − 126.9 GeV) by ATLAS (CMS) [19][20][21][22]. It has also been shown that in some regions of the parameter space another light, singlet-like, Higgs (h 0 1 ) can also be present, with a mass around 98 GeV [23][24][25][26][27], motivated by the small excess in the LEP search for e + e − → Zh, h → bb [28][29][30], or even lighter [26,[31][32][33][34][35].…”

“…Some of these scenarios also present a very light pseudoscalar Higgs boson, a 0 1 , [26,27,[31][32][33][34], which is very appealing from the point of view of LHC signatures. For example, in ref.…”

“…For example, in ref. [26] we investigated how a very light pseudoscalar in the mass range 2m τ < m a 0 1 < 2m b could be probed in multilepton decays of the scalar Higgses, h 0 1, 2 → a 0 1 a 0 1 → 4ℓ + E T / (where ℓ = e, µ, and hadronically-decaying τ , τ h and / E T denotes the missing transverse energy), and showed how the pseudoscalar mass can be reconstructed. Another remarkable effect of a light pseudoscalar is that it can be copiously produced in the decays of neutralinos χ 0 2,3 → χ 0 1 a 0 1 , constituting a characteristic NMSSM signature [35][36][37][38][39].…”

NMSSM interpretations of the observed Higgs signal

“…Several studies also suggested to exploit pair production processes at the LHC in order to distinguish the SM from the NMSSM and/or to look for a light singlet in this fashion [78][79][80][81][82][83]. Scenarios with a very light CP-odd (or CP-even) Higgs boson were addressed with several search proposals in direct production, unconventional light charged-Higgs decays, or cascade decays from SM-like / light singlet states; large Higgs-to-Higgs decays were also considered from the point of view of the SM-compatible nature of the observed state [84][85][86][87]. Recent studies of the properties of a light pseudoscalar in the NMSSM [88,89] have emphasized the relevance of indirect production modes for the investigation of this scenario at the LHC.…”