Browsing by Author "Nasri, Salah"

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    Effects of two inert scalar doublets on Higgs boson interactions and the electroweak phase transition
    (AMER PHYSICAL SOC, 2015) Ahriche, Amine; Faisel, Gaber; Ho, Shu-Yu; Nasri, Salah; Tandean, Jusak
    We study some implications of the presence of two new scalar weak doublets beyond the standard model which have zero vacuum expectation values and are charged under an extra Abelian gauge symmetry. The additional gauge sector does not couple directly to standard-model particles. We investigate specifically the effects of the scalars on oblique electroweak parameters and on the interactions of the 125 GeV Higgs boson, especially its decay modes h --> gamma gamma, gamma Z and trilinear self-coupling, all of which will be probed with improved precision in future Higgs measurements. Moreover, we explore how the new scalars may give rise to strongly first-order electroweak phase transition and also show its correlation with sizable modifications to the Higgs trilinear self-coupling.
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    Exploring high-mass diphoton resonance without new colored states
    (ELSEVIER SCIENCE BV, 2017) Ahriche, Amine; Faisel, Gaber; Nasri, Salah; Tandean, Jusak
    A new heavy resonance may be observable at the LHC if it has a significant decay branching fraction into a pair of photons. We entertain this possibility by looking at the modest excess in the diphoton invariant mass spectrum around 750 GeV recently reported in the ATLAS and CMS experiments. Assuming that it is a spinless boson, dubbed (s) over tilde, we consider it within a model containing two weak scalar doublets having zero vacuum expectation values and a scalar singlet in addition to the doublet responsible for breaking the electroweak symmetry. The model also possesses three Dirac neutral singlet fermions, the lightest one of which can play the role of dark matter and which participate with the new doublet scalars in generating light neutrino masses radiatively. We show that the model is consistent with all phenomenological constraints and can yield a production cross section sigma (pp -> (s) over tilde -> gamma gamma) of roughly the desired size, mainly via the photon-fusion contribution, without involving extra colored fermions or bosons. We also discuss other major decay modes of (s) over tilde which are potentially testable in upcoming LHC measurements. (C) 2017 The Author(s). Published by Elsevier B.V.