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 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.

Exploration of heavy Higgs bosons at a 100 TeV hadron collider within the semi-constrained next-to-minimal supersymmetric standard model

In this study,we explore the detectability of heavy Higgs bosons in the pp→bbH/A→bbtt channel at a100 TeV hadron collider within the semi-constrained next-to-minimal supersymmetric standard model.We calculate their production cross sections and decay branching ratios and compare them with simulation results from literature.We focus on the heavy doublet-dominated CP-even Higgs H and CP-odd Higgs A,with mass limits set below 10TeV to ensure detectability.At a collider with an integrated luminosity of 3 ab^(-1),the potential for detecting heavy Higgs bosons varies significantly with their mass and tanβ.Heavy Higgs bosons with masses below 2 TeV are within the testable range,while those heavier than 7 TeV are below the exclusion and discovery thresholds,rendering them undetectable.For masses between 2 and 7 TeV,heavy Higgs bosons with tanβ smaller than 20 can be detected,whereas those with tanβ larger than 20 are beyond the current discovery or exclusion capabilities.

R-Parity Violation Effects on b_1 → bχ_1~0 in Minimal SupersymmetricStandard Model

We investigate in detail the effects of R-parity lepton number violation onthe decay b_1 → bχ_1~0 in the R-parity violating minimal supersymmetric standard model (R_p-MSSM)under the present experimental constraints on R_p parameters. In our numerical calculations weconsider two cases of input parameters of the squark and slepton sectors, M_(squark) 【 M_(slepton)and M_(squark) 】 M_(slepton), for comparison. The results show that the relative R-parity violatingcorrection is not very sensitive to the mass of the lightest neutralino bχ_1~0 the degenerateR-parity violating coupling parameter λ′_2 but strongly depends on M_(squark), M_(slepton) tan βand tie degenerate R-parity violating coupling parameter λ′_1. The relative correction is about -4～ 3% and can exceed -6% in some region of parameter space. Therefore, precise experiment analyseson the decay b_1 → bχ_1~0 may provide a probe of the R-parity violation.

The Top-Charm Associated Production Within the R-Parity Violating Supersymmetric Model in Photon-Proton Collisions

The top-charm associated production with the effects from both B- and L-violating interactions in TeVscale photon-proton collisions is investigated in the framework of Rp minimal supersymmetric standard model. Withinthe bounds on the relevant R-parity violating couplings, the total cross section will reach the order of 10 fb in some partsof the parameter space.

The Top－Charm Associated Production Within the R－Parity Violating Supersymmetric Model in Photon－Proton Collisions

The top-charm associated production with the effects from both B- and L-violating interactions in TeV scale photon-proton collisions is investigated in the framework of minimal supersymmetric standard model. Within the bounds on the relevant R-parity violating couplings, the total cross section will reach the order of 10 fb in some parts of the parameter space.

Supersymmetric Electroweak Corrections to the Decay of the Heavy Chargino into the Light Chargino and Z Boson

The supersymmetric electroweak corrections to the partial width of the decay x2+ → Z0x1-+, including thecontributions from the third generation quarks and squarks, are presented within the minimal supersymmetric standardmodel. With the reasonable parameters sets, which open this decay channel kinematically, the relative corrections canreach the value of ～ -6%. Therefore they should be taken into consideration for the precise experimental measurementat future colliders.

Effects of Complex Parameters on t→ch^0 in Supersymmetric QCD

We investigate the leading SUSY-QCD contributions to the branch ratio (BR) oft→ch~0 within the context of the minimal supersymmetric standard model (MSSM) with complex parameters,assuming more generally that there is a misalignment between the squark and quark that leads to a flavor non-diagonal squark mass matrix.We introduce complex phases only in μ and At,namely φ_μ and φ_(Aq),for simplicity,and study the dependence of the BR of t→ch~0 on these phase parameters.Our calculations show that these CP-violation phases and the flavor mixing parameter λ influence the BR oft→ch~0 considerably,and the effect induced by φ_(At) is much larger than that by φ_μ and φ_(Ac(?)u.For different values of the complex parameters μ and A_t that are set in this paper,the BR of t -+ ch~ is in the range of 10~(-7)～10~(-6),depending mainly on the value of the trilinear coupling A_t.

强子对撞机上荷电Higgs玻色子的研究

通过Top夸克衰变,在最小超对称标准模型下,在强子对撞机上相继讨论了寻找轻、重带电Higgs玻色子的前景.结果表明:在LHC上,在mH+≥140 GeV及tanβ≤1条件下,三体衰变道提供了质量较轻的荷电Higgs玻色子的可观测信号;而对于质量较重的荷电Higgs玻色子,在tanβ较大区域内,H±→τv是可观测道.

B→ X8γ, X8l＋l- Decays and Constraints on Mass Insertion Parameters in MSSM

In this paper, we study the upper bounds on the mass insertion parameters （δAB^q）ij in the minimal super symmetric standard model. We found that the information from the measured branching ratio of B→ X8γ, X8l＋l- decay can help us to improve the upper bounds on the mass insertions parameters （δAB^u,d）3j,i3 Some regions allowed by the data of Br（B→ X8γ） are excluded by the requirement of an SM-like C7γ （rnb） imposedby the data of Br（B→ X8γ, X8l＋l- ）.

On Gaugino Dominated Dark Matter

Using the neutral gauginos of and hybridization ideas below the GUT scale, we approach the Dark Matter particle within the Minimal Supersymmetric Standard Model. In the energy range where supergravity effects can be ignored, it is proposed that such DM particle could be inter- preted in terms of a mixture of Bino and Wino states with a lower bound mass not far above the electroweak scale to account for the observed Dark Matter density. We establish the theoretical origin of this particle and study as well its compositeness and its mass bound.

R-宇称破缺的相互作用研究

在LHC上,最小超对称标准模型中R-宇称破缺相互作用使LHC上tt—对的产生有两种过程,一种是交换slepton粒子的t道的dR-dR→tLt—L过程,一种是交换squark粒子的u道的dRd-R→tRt—R过程.这样的top夸克对的产生机理会使tt—事例中的top夸克产生极化不对称现象.研究发现,由于LHC较高的统计性,在LHC上top夸克极化的统计灵敏度以及限定相应的R-宇称破缺耦合常数的能力均比Tevatron upgrade上的强.

包含轻子结构的夸克模型

对标准模型作手征性扩充后，模型中平行地存在手征性相反的夸克态．相应于构成强子的ｆ代普通夸克，新加的同样代数、手征性相反的夸克可能构成轻子．对扩充后的模型超对称化之后，使得渐近自由性质的破坏所要求的代的数目从大于３３／８减少到大于９／４，从而有可能解释手征相反的夸克构成的轻子为什么比普通夸克构成的强子大小要小得多等特点．

Pair production of Higgs boson in NMSSM at the LHC with the next-to-lightest C P-even Higgs boson being SM-like

The next-to-minimal supersymmetric standard model （NMSSM） more naturally accommodates a Higgs boson with a mass of approximately 125 GeV than the minimal supersymmetric standard model （MSSM）. In this work, we assume that the next-to-lightest CP-even Higgs boson h2 is the SM-like Higgs boson h, whereas the lightest CP-even Higgs boson h1 is dominantly singlet-like. We discuss the h1h1, h2h2, and h1h2 pair production processes via gluon-gluon fusion at the LHC for an collision energy of 14 TeV, and we consider the cases in which one Higgs boson decays to bb and the other decays to γγ or τ＋τ-. We find that, for mh1？ 62 GeV, the cross section of the gg→h1h1 process is relatively large and maximally reaches 5400 fb, and the production rate of the h1h1→bbτ＋τ-final state can reach 1500 fb, which make the detection of this final state possible for future searches of an integrated luminosity of 300 and 3000 fb-1. This is mainly due to the contributions from the resonant production process pp→h2→h1h1 and the relatively large branching ratio of h1→bb and h1→τ＋τ-. The cross sections of the pp→h2h2 and pp→h1h2 production processes maximally reach 28 fb and 133 fb, respectively.