arXiv subjects

C. Hugonie

Publications and source records attributed to C. Hugonie.

28 records · Page 2Linked to original sources

arXiv2001

Higgs Sector of Non-minimal Supersymmetric Models at Future Hadron Colliders

We investigate the potential of current and planned hadron colliders operating at the TeV scale in disentangling the structure of the Higgs sector of non-minimal Supersymmetric extensions of the Standard Model with an extra gauge singlet. We assume universality of the soft Supersymmetry breaking terms at the GUT scale as well as a CP-even Higgs boson with mass around 115 GeV, as suggested by LEP. We find that mixing angles between the doublet and singlet Higgs states are always small. However, concrete prospects exist at both the Tevatron (Run II) and the Large Hadron Collider of detecting at least one neutral Higgs state with a dominant singlet component, in addition to those available from a doublet Higgs sector which is similar to the one of the Minimal Supersymmetric Standard Model.

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arXiv2000

Phenomenology of a New Minimal Supersymmetric Extension of the Standard Model

We study the phenomenology of a new Minimally-extended Supersymmetric Standard Model (nMSSM) where a gauge singlet superfield is added to the MSSM spectrum. The superpotential of this model contains no dimensionful parameters, thus solving the mu-problem of the MSSM. A global discrete R-symmetry, forbidding the cubic singlet self-interaction, imposed on the complete theory, guarantees its stability with respect to generated higher-order tadpoles of the singlet and solves both the domain wall and Peccei-Quinn axion problems. We give the free parameters of the model and display some general constraints on them. A particular attention is devoted to the neutralino sector where a (quasi-pure) singlino appears to be always the LSP of the model, leading to additional cascades, involving the NLSP -> LSP transition, compared with the MSSM. We then present the upper bounds on the masses of the lightest and next-to-lightest -- when the lightest is an invisible singlet -- CP-even Higgs bosons, including the full one-loop and dominant two-loop corrections. These bounds are found to be much higher than the equivalent ones in the MSSM. Finally, we discuss some phenomenological implications for the Higgs sector of the nMSSM in Higgs production at future hadron colliders.

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arXiv2000

Does LEP prefer the NMSSM?

We study the naturalness of electroweak symmetry breaking and baryogenesis in the next-to-minimal supersymmetric standard model (NMSSM). Our study is motivated by the recent LEP bounds on the Higgs boson mass which severely constrains the low \tanβregion of the minimal supersymmetric standard model (MSSM). We show that the low \tan βregion of the NMSSM is clearly favoured over the MSSM with regard to the physical Higgs boson mass, fine-tuning, and electroweak baryogenesis.

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arXiv2000

Report of the Beyond the MSSM Subgroup for the Tevatron Run II SUSY/Higgs Workshop

There are many low-energy models of supersymmetry breaking parameters which are motivated by theoretical and experimental considerations. Here, we discuss some of the lesser-known theories of low-energy supersymmetry, and outline their phenomenological consequences. In some cases, these theories have more gauge symmetry or particle content than the Minimal Supersymmetric Standard Model. In other cases, the parameters of the Lagrangian are unusual compared to commonly accepted norms (e.g., Wino LSP, heavy gluino LSP, light gluino, etc.). The phenomenology of supersymmetry varies greatly between the different models. Correspondingly, particular aspects of the detectors assume greater or lesser importance. Detection of supersymmetry and the determination of all parameters may well depend upon having the widest possible view of supersymmetry phenomenology.

hep-ph↗

arXiv2000

Higgs masses and couplings in the NMSSM

We give the upper bounds on the masses of the lightest and second lightest CP even Higgs bosons in the NMSSM, the MSSM extended by a gauge singlet. The dominant two loop corrections are included. Since the coupling R of the lightest Higgs scalar to gauge bosons can be small, we study in detail the relation between masses and couplings of both lightest scalars. We present upper bounds on the mass of a 'strongly' coupled Higgs (R>1/2) as a function of lower experimental limits on the mass of a 'weakly' coupled Higgs (R<1/2). With the help of these results, the whole parameter space of the model can be covered.

hep-ph↗

arXiv2000

Masses and Couplings of the Lightest Higgs Bosons in the (M+1)SSM

We study the upper limits on the mass of the lightest and second lightest CP even Higgs bosons in the (M+1)SSM, the MSSM extended by a gauge singlet. The dominant two loop contributions to the effective potential are included, which reduce the Higgs masses by 10 GeV. Since the coupling R of the lightest Higgs scalar to gauge bosons can be small, we study in detail the relations between the masses and couplings of both lightest scalars. We present upper bounds on the mass of a 'strongly' coupled Higgs (R > 1/2) as a function of lower experimental limits on the mass of a 'weakly' coupled Higgs (R < 1/2). With the help of these results, the whole parameter space of the model can be covered by Higgs boson searches.

hep-ph↗

arXiv1999

Topologies of the (M+1)SSM with a Singlino LSP at LEP2

We study the possible signals of the (M+1)SSM with a singlino LSP at LEP2. First we identify regions of the parameter space which are ruled out by negative results of sparticle searches in the context of the MSSM. In the remaining kinematically accessible regions we present total event rates for topologies which require further studies, i.e. estimations of the corresponding efficiencies: various 4 charged fermion final states with missing energy, possibly with displaced vertices due to a long lifetime of the NLSP, the second lightest neutralino. Searches for these unconventional signatures are essential in order to cover the entire kinematically accessible parameter space of the (M+1)SSM with a singlino LSP at LEP2.

hep-ph↗

arXiv1999

Constraints from Charge and Colour Breaking Minima in the (M+1)SSM

We study the constraints on the parameter space of the supersymmetric standard model extended by a gauge singlet, which arise from the absence of global minima of the effective potential with slepton or squark vevs. Particular attention is paid to the so-called ``UFB'' directions in field space, which are F-flat in the MSSM. Although these directions are no longer F-flat in the (M+1)SSM, we show that the corresponding MSSM-like constraints on m_0/M_{1/2} apply also to the (M+1)SSM. The net effect of all constraints on the parameter space are more dramatic than in the MSSM. We discuss the phenomenological implications of these constraints.

hep-ph↗

arXiv1999

Cascade Decays in the NMSSM

We study unconventional signatures of the NMSSM (the MSSM with an additional gauge singlet) with a singlino LSP. Compared to sparticle production processes in the MSSM, these consist in additional cascades (one or two additional l+ l-, tau+ tau- or b bbar pairs or photons), possibly with macroscopically displaced vertices with distances varying from millimeters to several meters.

hep-ph↗

arXiv1998

Neutralino Cascades in the (M+1)SSM

In the (M+1)SSM an additional gauge singlet Weyl spinor appears in the neutralino sector. For a large part of the parameter space this approximative eigenstate is the true LSP. Then most sparticle decays proceed via an additional cascade involving the NLSP -> LSP transition, where the NLSP is the non-singlet next-to-lightest neutralino. We present a comprehensive list of all processes, which contribute to the NLSP -> LSP transition, the partial widths and the total NLSP decay rate. We perform a scan of the parameters of the model compatible with universal soft terms, and find that the NLSP life time can be quite large, leading to macroscopically displaced vertices. Our results imply that the signatures for sparticle production in the (M+1)SSM can be very different from the MSSM, and are important for calculations of the abundance of dark matter in this model.

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