Study of diphoton decays of the lightest scalar Higgs boson in the Next-to-Minimal Supersymmetric Standard Model

The CMS and ATLAS experiments at the LHC have announced the discovery of a Higgs boson with mass at approximately 125 GeV/c2 in the search for the Standard Model Higgs boson via, notably, the 2/y and ZZ to four leptons final states. Considering the recent results of the Higgs boson searches from the LHC, we study the lightest scalar Higgs boson hi in the Next-to-Minimal Supersymmetric Standard Model by restricting the next-to- lightest scalar Higgs boson h2 to be the observed to the 125 GeV/c2 state. We perform a scan over the relevant NMSSM parameter space that is favoured by low fine-tuning considerations. Moreover, we also take the experimental constraints from direct searches, B-physics observables, relic density, and anomalous magnetic moment of the muon measurements, as well as the theoretical considerations, into account in our specific scan. We find that the signal rate in the two-photon final state for the NMSSM Higgs boson hi with the mass range from about 80 GeV/e2 to about 122 CeV/c2 can be enhanced by a factor of up to 3.5 when the Higgs boson h2 is required to be compatible with the excess from latest LHC results. This motivates the extension of the search at the LHC for the Higgs boson hi in the diphoton final state down to masses of 80 GeV/c2, particularly with the upcoming proton-proton collision data to be taken at center-of-mass energies of 13-14 TeV.

Search for a lighter neutral custodial fiveplet scalar in the Georgi-Machacek model

Many researches from both theoretical and experimental perspectives have been performed to search for a new Higgs Boson that is lighter than the 125 GeV Higgs boson,which was discovered at the LHC in 2012.In this study,we explore the possibility of constraining a lighter neutral custodial fiveplet scalar H_(5)^(0) in the GeorgiMachacek(GM) model using the latest results of the search for a lighter Higgs boson decaying into two photons from LHC data.The custodial-singlet mass eigenstate h or H is considered to be the LHC observed 125 GeV Higgs boson.A new set of constrained parameters that is favoured by low-mass H_(5)^(0) is proposed to generate events efficiently.The production of H_(5)^(0) from a scan based on the constrained parameters is compared to the latest results of the search for a lighter Higgs boson decaying into two photons by the CMS Collaboration after applying theoretical constraints from the GM model and constraints from all existing relevant experimental measurements,including the recent results of the Higgs boson searches by the LHC.Numerical analyses of the surviving GM parameter space are performed.The tendencies and correlations of the GM input parameters from phenomenological studies are summarized.In addition,the discovery potential of the other interesting decay channels of this low-mass neutral custodial fiveplet scalar are discussed.

Search for a lighter Higgs boson in the Next-to-Minimal Supersymmetric Standard Model

Following the discovery of the Higgs boson with a mass of approximately 125 GeV at the LHC, many studies have been performed from both the theoretical and experimental viewpoints to search for a new Higgs Boson that is lighter than 125 GeV. We explore the possibility of constraining a lighter neutral scalar Higgs boson hi and a lighter pseudo-scalar Higgs boson al in the Next-to-Minimal Supersymmetric Standard Model by restricting the next-to-lightest scalar Higgs boson h2 to be the one observed at the LHC after applying the phenomenological constraints and those from experimental measurements. Such lighter particles are not yet completely excluded by the latest results of the search for a lighter Higgs boson in the diphoton decay channel from LHC data. Our results show that some new constraints on the Next-to-Minimal Supersymmetric Standard Model could be obtained for a lighter scalar Higgs boson at the LHC if such a search is performed by experimental collaborations and more data. The potentials of discovery for other interesting decay channels of such a lighter neutral scalar or pseudo-scalar particle are also discussed.