arXiv subjects

Amine Ahriche

Publications and source records attributed to Amine Ahriche.

At least 37 records · Page 2Linked to original sources

arXiv2018

Gravitational Waves from Phase Transitions in Models with Charged Singlets

We investigate the effect of extra singlets on the electroweak phase transition (EWPT) strength and the spectrum of the corresponding gravitational waves (GWs). We consider here the standard model (SM) extended with a singlet scalar with multiplicity N coupled to the SM Higgs doublet. After imposing all the theoretical and experimental constraints and defining the region where the EWPT is strongly first order, we obtain the region in which the GWs spectrum can be reached by different future experiments such as LISA and DECIGO.

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arXiv2018

Radiative Neutrino Mass & Majorana Dark Matter within an Inert Higgs Doublet Model

We consider an extension of the standard model (SM) with an inert Higgs doublet and three Majorana singlet fermions to address both origin and the smallness of neutrino masses and dark matter (DM) problems. In this setup, the lightest Majorana singlet fermion plays the role of DM candidate and the model parameter space can be accommodated to avoid different experimental constraints such as lepton flavor violating processes and electroweak precision tests. The neutrino mass is generated at one-loop level a la Scotogenic model and its smallness is ensured by the degeneracy between the CP-odd and CP-even scalar members of the inert doublet. Interesting signatures at both leptonic and hadronic colliders are discussed.

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arXiv2018

Right-Handed Neutrinos: DM and LFV $vs$ Collider

In a class of neutrino mass models with a lepton flavor violation (LFV) Yukawa interaction term that involves a heavy right handed neutrino, a charged scalar and a charged lepton, we investigate at the ILC@500 GeV the possibility of observing news physics. These models can address neutrino mass and dark matter without being in conflict with different LFV constraints. By imposing DM relic density and LFV constraints, we recast the analysis done by L3 collaboration at LEP-II of monophoton searches on our space parameter and look for new physics in such channels like monophoton and $S S(γ)$, where we give different cuts and show the predicted distributions. We show also that using polarized beams could improve the statistical significance.

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arXiv2017

Identifying the nature of dark matter at $e^{-}e^{+}$ Colliders

In this work, we consider the process $e^{+}+e^{-}\rightarrow b\bar{b}+\slashed{E}_{T}$, at the future electron-positron colliders such as the International Linear Collider and Compact Linear Collider, to look for the dark matter (DM) effect and identify its nature at two different center-of-mass energies $E_{c.m.}=500~\mathrm{GeV}~and~1~\mathrm{TeV}$. For this purpose, we take two extensions of the standard model, in which the DM could be a real scalar or a heavy right-handed neutrino (RHN) similar to many models motivated by neutrino mass. In the latter extension, the charged leptons are coupled to the RHNs via a lepton flavor violating interaction that involves a charged singlet scalar. After discussing different constraints, we define a set of kinematical cuts that suppress the background, and generate different distributions that are useful in identifying the DM nature. The use of polarized beams (like the polarization $P(e^{-},e^{+})=\left[+0.8,-0.3\right]$ at the International Linear Collider) makes the signal detection easier and the DM identification more clear, where the statistical significance gets enhanced by twice (five times) for scalar (RHN) DM.

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arXiv2017

Right-handed neutrinos: dark matter, lepton flavor violation and leptonic collider searches

We examine lepton flavor violating (LFV) interactions for heavy right-handed neutrinos that exist in most of the standard model extensions that address dark matter (DM) and neutrino mass at the loop level. In order to probe the collider effect of these LFV interactions, we impose the assumption that the model parameters give the right values of the DM relic density and fulfill the constraints from the LFV processes $\ell_α\rightarrow\ell_βγ$ and $\ell_α\rightarrow3\ell_β$. We also investigate the possibility of probing these interactions, and hence the right-handed neutrino, at leptonic colliders through different final state signatures.

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arXiv2017

Probing Radiative Neutrino Mass Models At The LHC Via Trilepton Events

Trilepton event represents one of the probes of the new physics at high energy colliders. In this talk, we consider the search for processes with final states $\ell_α^{\pm }\ell_β^{\pm}\ell_γ^{\mp}$ + $\slashed{E}_{T}$ where $α$, $β$, $γ$= $e,μ,τ$, via the production of singlet charged scalar $S^{\pm}$ which arise in a class of radiative neutrino mass models. We discuss the opposite sign same flavor leptons signal, as well as the background free channel in view to get a significant excess at $\sqrt{s}$= 8 TeV and $\sqrt{s}$ = 14 TeV at the hadron collider LHC.

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arXiv2017

Exploring high-mass diphoton resonance without new colored states

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 $\tilde s$, 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 $σ(pp\rightarrow\tilde{s}\rightarrowγγ)$ 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 $\tilde s$ which are potentially testable in upcoming LHC measurements.

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arXiv2016

Probing Radiative Neutrino Mass Models Using Trilepton Channel at the LHC

In this work, we probe a class of neutrino mass models through the lepton flavor violating interactions of a singlet charged scalar, $S^{\pm}$ at the LHC proton-proton collisions with 8 TeV and 14 TeV energies. This scalar couples to the leptons and induces many processes such as $pp\rightarrow\ell^{\pm}\ell^{\pm}\ell^{\mp}+\slashed{E}_{T}$. In our analysis we discuss the opposite sign same flavor leptons signal, as well as the background free channel with the tau contribution which can enhance the signal/background ratio for center of mass energies $\sqrt{s}$= 8 TeV and $\sqrt{s}$ = 14 TeV.

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arXiv2016

Probing Radiative Neutrino Mass Models With Dilepton Events At The LHC

In this work we prob a class of neutrino mass models at both Large Hadron Collider (LHC) energies 8 TeV and 14 TeV. The focus will be on the new introduced interaction terms between a singlet charged scalar, $S^{\pm}$, and leptons leading to different final states $pp\rightarrow\ell_α^{\pm}\ell_β^{\mp}$ +$\slashed E$ with $\ell_α\ell_β=ee,eμ,μμ$ that implies lepton flavor violation (LFV). An accurate cut on the $M_{T2}$ eventvariable is found to be crucial for an effective suppression of the large Standard Model background. The obtained results can be translated into a possible detectability of the charged scalars effect..

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arXiv2016

Scale-Invariant Models with One-Loop Neutrino Mass and Dark Matter Candidates

We construct a list of minimal scale-invariant models at the TeV scale that generate one-loop neutrino mass and give viable dark matter candidates. The models generically contain a singlet scalar and a $Z_2$-odd sector comprised of singlet, doublet and/or triplet SU(2) multiplets. The dark matter may reside in a single multiplet or arise as an admixture of several multiplets. We find fifteen independent models, for which the dark matter is a viable candidate and neutrino mass results from a diagram with just one of the irreducible scale-invariant one-loop topologies. Further "non-pure" cases give hybrid one-/two-loop masses. All models predict new TeV scale physics, including a singlet scalar that generically mixes with the Higgs boson.

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arXiv2016

The Scale-Invariant Scotogenic Model

We investigate a minimal scale-invariant implementation of the scotogenic model and show that viable electroweak symmetry breaking can occur while simultaneously generating one-loop neutrino masses and the dark matter relic abundance. The model predicts the existence of a singlet scalar (dilaton) that plays the dual roles of triggering electroweak symmetry breaking and sourcing lepton number violation. Important constraints are studied, including those from lepton flavor violating effects and dark matter direct-detection experiments. The latter turn out to be somewhat severe, already excluding large regions of parameter space. None the less, viable regions of parameter space are found, corresponding to dark matter masses below (roughly) 10 GeV and above 200 GeV.

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arXiv2016

A Critical Analysis of One-Loop Neutrino Mass Models with Minimal Dark Matter

A recent paper investigated minimal R$ν$MDM models with the type T1-iii and T3 one-loop topologies. However, the candidate most-minimal model does not possess an accidental symmetry - the scalar potential contains an explicit symmetry breaking term, rendering the dark matter unstable. We present two models that cure this problem. However, we further show that all of the proposed minimal one-loop R$ν$MDM models suffer from a second problem - an additional source of explicit $Z_2$ symmetry breaking in the Yukawa sector. We perform a more-general analysis to show that neutrino mass models using either the type T3 or type T1-iii one-loop topologies do not give viable minimal dark matter candidates. Consequently, one-loop models of neutrino mass with minimal dark matter do not appear possible. Thus, presently there remains a single known (three-loop) model of neutrino mass that gives stable dark matter without invoking any new symmetries.

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arXiv2016

Probing Radiative Neutrino Mass Models with Dilepton Events at the LHC

In this work, we investigate the possibility of probing a class of neutrino mass models at the LHC proton-proton collisions with 8 and 14 TeV energies. The existence of lepton flavor violating interactions for a singlet charged scalar, $S^{\pm}$, that couples to the leptons could induce many processes such as $pp\rightarrow\ell_α^{\pm}\ell_β^{\mp}+\slashed E $. Using the processes with $\ell_α\ell_β=ee,eμ,μμ$, we found that an inclusive cut on the $M_{T2}$ event variable is vital in our analysis and leads to an effective suppression of the large Standard Model background. Our results show possible detectability of the charged scalars effect, especially at the $\sqrt{s}= 14~\text{TeV}$.

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arXiv2016

Dark Radiative Inverse Seesaw Mechanism

We present a minimal model that simultaneously accounts for neutrino masses and the origin of dark matter (DM) and where the electroweak phase transition is strong enough to allow for electroweak baryogenesis. The Standard Model is enlarged with a Majorana fermion, three generations of chiral fermion pairs, and a single complex scalar that plays a central role in DM production and phenomenology, neutrino masses, and the strength of the phase transition. All the new fields are singlets under the SM gauge group. Neutrino masses are generated via a new variant of radiative inverse seesaw where the required small mass term is generated via loops involving DM and no large hierarchy is assumed among the mass scales. The model offers all the advantage of low-scale neutrino mass models as well as a viable dark matter candidate that is testable with direct detection experiments.

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arXiv2016

A Radiative Model for the Weak Scale and Neutrino Mass via Dark Matter

We present a three-loop model of neutrino mass in which both the weak scale and neutrino mass arise as radiative effects. In this approach, the scales for electroweak symmetry breaking, dark matter, and the exotics responsible for neutrino mass, are related due to an underlying scale-invariance. This motivates the otherwise-independent O(TeV) exotic masses usually found in three-loop models of neutrino mass. We demonstrate the existence of viable parameter space and show that the model can be probed at colliders, precision experiments, and dark matter direct-detection experiments.

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arXiv2015

A Model of Neutrino Mass and Dark Matter with an Accidental Symmetry

We present a model of radiative neutrino mass that automatically contains an accidental $Z_2$ symmetry and thus provides a stable dark matter candidate. This allows a common framework for the origin of neutrino mass and dark matter without invoking any symmetries beyond those of the Standard Model. The model can be probed by direct-detection experiments and $μ\rightarrow e+γ$ searches, and predicts a charged scalar that can appear at the TeV scale, within reach of collider experiments.

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arXiv2015

Effects of Two Inert Scalar Doublets on Higgs Interactions and Electroweak Phase Transition

We study some implications of the presence of two inert scalar doublets which are charged under a dark Abelian gauge symmetry. Specifically, we investigate the effects of the new scalars on oblique electroweak parameters and on the interactions of the 125 GeV Higgs boson, especially its decay modes $h\toγγ,γZ$, and trilinear coupling, all of which will be probed with improved precision in future Higgs measurements. Moreover, we explore how the inert scalars may give rise to strongly first-order electroweak phase transition and also show its correlation with sizable modifications to the Higgs trilinear coupling.

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arXiv2015

Scalar Sector Phenomenology of Three-Loop Radiative Neutrino Mass Models

We perform a phenomenological study of the scalar sector of two models that generate neutrino mass at the three-loop level and contain viable dark matter candidates. Both models contain a charged singlet scalar and a larger scalar multiplet (triplet or quintuplet). We investigate the effect of the extra scalars on the Higgs mass and analyze the modifications to the triple Higgs coupling. The new scalars can give observable changes to the Higgs decay channel $h\rightarrowγγ$ and, furthermore, we find that the electroweak phase transition becomes strongly first-order in large regions of parameter space.

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