Ref HAL: hal-00724467_v1
Ref Arxiv: 1112.5453
DOI: 10.1007/JHEP04(2012)136
WoS: 000304148100062
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101 Citations
Résumé:

We study the two photon decay channel of the Standard Model-like component of the CP-even Higgs bosons present in the type II Seesaw Model. The corresponding cross-section is found to be significantly enhanced in parts of the parameter space, due to the (doubly-)charged Higgs bosons' $(H^{\pm \pm})H^\pm$ virtual contributions, while all the other Higgs decay channels remain Standard Model(SM)-like. In other parts of the parameter space $H^{\pm \pm}$ (and $H^{\pm}$) interfere destructively, reducing the two photon branching ratio tremendously below the SM prediction. Such properties allow to account for any excess such as the one reported by ATLAS/CMS at $\approx 125$ GeV if confirmed by future data; if not, for the fact that a SM-like Higgs exclusion in the diphoton channel around 114-115 GeV as reported by ATLAS, does not contradict a SM-like Higgs at LEP(!), and at any rate, for the fact that ATLAS/CMS exclusion limits put stringent lower bounds on the $H^{\pm \pm}$ mass, particularly in the parameter space regions where the direct limits from same-sign leptonic decays of $H^{\pm \pm}$ do not apply.

Commentaires: 26 pages, 7 figures

Ref HAL: hal-00653505_v1
Ref Arxiv: 1111.3455
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Résumé:

We consider no-scale supergravity inspired scenarios, emphasizing the possible dynamical determination of the soft supersymmetry-breaking parameters as triggered by the radiative corrections that lift an essentially flat tree-level potential in the hidden sector. We (re)emphasize the important role played by the scale-dependent vacuum energy contribution to the effective potential for the occurrence of consistent no-scale minima. The most relevant input parameters are introduced as $B_0$ (the soft breaking mixing Higgs parameter) and $\eta_0$ (the cosmological constant value at high energy) instead of $\mhalf$ and $\tan \beta$, the latter being determined through a (generalized) potential minimization at electroweak scales. We examine the theoretical and phenomenological viability of such a mechanism when confronted with up-to-date calculations of the low energy sparticle spectrum and with present constraints from the LHC and other observables. The tight dark matter relic density constraint for a neutralino LSP scenario can be considerably relaxed for a gravitino LSP scenario possible in this framework.

Commentaires: Proceedings of the 2011 Europhysics Conference on High Energy Physics, EPS-HEP 2011, July 21-27, 2011 Grenoble, Rhône-Alpes, France

Ref HAL: hal-00608687_v1
Ref Arxiv: 1105.1925
DOI: 10.1103/PhysRevD.84.095005
WoS: 000296889700003
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165 Citations
Résumé:

The standard model Higgs sector, extended by one weak gauge triplet of scalar fields with a very small vacuum expectation value, is a very promising setting to account for neutrino masses through the so-called type II seesaw mechanism. In this paper we consider the general renormalizable doublet/triplet Higgs potential of this model. We perform a detailed study of its main dynamical features that depend on five dimensionless couplings and two mass parameters after spontaneous symmetry breaking, and highlight the implications for the Higgs phenomenology. In particular, we determine (i) the complete set of tree-level unitarity constraints on the couplings of the potential and (ii) the exact tree-level boundedness from below constraints on these couplings, valid for all directions. When combined, these constraints delineate precisely the theoretically allowed parameter space domain within our perturbative approximation. Among the seven physical Higgs states of this model, the mass of the lighter (heavier) CPeven state h(0) (H-0) will always satisfy a theoretical upper (lower) bound that is reached for a critical value mu(c) of mu (the mass parameter controlling triple couplings among the doublet/triplet Higgses). Saturating the unitarity bounds, we find an upper bound m(h)(0) < O(0.7-1 TeV), while the upper bound for the remaining Higgses lies in the range of several tens of TeV. However, the actual masses can be much lighter. We identify two regimes corresponding to mu greater than or similar to mu(c) and mu less than or similar to mu(c). In the first regime the Higgs sector is typically very heavy, and only h(0) that becomes SM-like could be accessible to the LHC. In contrast, in the second regime, somewhat overlooked in the literature, most of the Higgs sector is light. In particular, the heaviest state H-0 becomes SM-like, the lighter states being the CPodd Higgs, the (doubly) charged Higgses, and a decoupled h(0), possibly leading to a distinctive phenomenology at the colliders.

Commentaires: 55 pages, 9 figures, no major changes, references added, a comment added to sec 3.1, typos corrected

Ref HAL: hal-00608561_v1
Ref Arxiv: 1106.6325
DOI: 10.1103/PhysRevD.84.075015
WoS: WOS:000296882900001
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4 Citations
Résumé:

We consider no-scale inspired supergravity scenarios, where the gravitinomass and related soft supersymmetry-breaking parameters are determineddynamically by radiative corrections to an essentially flat tree-levelpotential in the supersymmetry breaking hidden sector. We examine thetheoretical and phenomenological viability of such a mechanism, when includingup-to-date calculations of the low energy sparticle spectrum and taking intoaccount the latest LHC results and other experimental constraints. We(re)emphasize the role of the scale-dependent vacuum energy contribution to theeffective potential, in obtaining realistic no-scale electroweak minima,examining carefully the impact of boundary conditions and of variants of theminimization procedure. We also discuss and implement the B_0 (soft breakingHiggs mixing parameter) input boundary condition at high scale, thereforefixing tan beta(B_0) at low scales. For general high scale boundary conditionswith non-vanishing B_0, m_0..., our analysis provides theoretical correlationsamong the supersymmetric, soft and vacuum energy parameters and relatedphenomenological consequences at the LHC. For instance, a zero vacuum energy atthe GUT scale would lead to a decoupled supersymmetric spectrum, together witha light standard model-like Higgs boson at the electroweak scale. Given theexperimental exclusion limits, a substantial class of the boundary conditions,and in particular the strict no-scale with m_0=A_0=B_0=0, are only compatiblewith a stau being the lightest MSSM particle. Then an enlarged allowedparameter space emerges when assuming a gravitino LSP to account for theobserved dark matter relic density.

Ref HAL: hal-00652618_v1
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Résumé:

I report on some scenarios where the gravitino is the dark matter and the supersymmetry breaking mediated by a gauge sector.

Ref HAL: hal-00612593_v1
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Résumé:

The purpose of this discussion contribution is to suggest the possibility that the imaginary action model could function as a cut off in loop diagrams. We argue also that the complex action model of M. Ninomiya and H.B. Nielsen has the DeBroglie-Bohmparticle appearing by itself, which is in a way already present in the contribution to this conference

Commentaires: Proceedings arXiv Id: 1012.0224

Ref HAL: hal-00612260_v1
Ref Arxiv: 1012.0224
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Résumé:

We give a short account of an old and somewhat unfashionable approach to quantum mechanics, arguing though for its potential to provide a new kind of Higgsless physics beyond the Standard Model.

Commentaires: Contains articles by different authors presented at the 13th Workshop 'What Comes Beyond the Standard Models', 12. - 22. July 2010, Bled, Slovenia. Editors were N.S. Mankoc Borstnik, H.B. Nielsen, D. Lukman, x + 233 pp Journal: Bled Workshops in Physics, Vol.11, No. 2, DMFA-Zaloznistvo, Ljubljana, Dec. 2010