Search

In this work, we investigate the possibility to address the excess observed around 95 GeV in the $\gamma\gamma$, $\tau\tau$, and $b\bar{b}$ channels as a scalar resonance(s) within the Georgi-Machacek (GM) model. In our analysis, we find that the excess can be easily accommodated in the channels ($\gamma\gamma$ and $b\bar{b}$) simultaneously, where the 95 GeV candidate is a single peak resonance (SPR) due to a light CP-even scalar. We found that the excess in the $\tau\tau$ channel can be addressed simultaneously with $\gamma\gamma$ and $b\bar{b}$ only if the 95 GeV candidate is a twin peak resonance (TPR), i.e., another CP-odd scalar in addition to the CP-even scalar. We demonstrate that the nature of the 95 GeV scalar resonance candidate (SPR or TPR) can be probed via the properties of its di-$\tau$ decay., Comment: 12 pages & 4 figures. Published version

The anomalies observed in the $W$ mass measurements at the CDF-II experiments and the excesses seen around 95~GeV at the Large Hadron Collider (LHC) motivate this work, in which we investigate and constrain the parameter space of the Scale Invariant Scotogenic Model with a Majorana dark matter candidate. The scanned parameters are chosen to be consistent with the dark matter relic density and the observed excesses at $\sim95$~GeV signal strength rates in different channels. We found that significant part of the viable space addresses the excess in the channel $\gamma\gamma$, while a tight part can address the excess in both $\gamma\gamma$ and $b\bar{b}$ channels. Furthermore, the model's viable parameters can be probed in both the LHC and future $e^{+}e^{-}$ colliders for di-Higgs production., Comment: 12 pages, 1 table, 4 captioned figures, accepted version to be appear in Physical Review D

We investigate the properties of the gravitational waves (GWs) generated during a strongly first order electroweak phase transition (EWPT) in models with the classical scale invariance (CSI). Here, we distinguish two parameter space regions that correspond to the cases of (1) light dilaton and (2) purely radiative Higgs mass (PRHM). In the CSI models, the dilaton mass, or the Higgs mass in the PRHM case, in addition to some triple scalar couplings are fully triggered by the radiative corrections (RCs). In order to probe the RC effects on the EWPT strength and on the GW spectrum, we extend the standard model by a real singlet to assist the electroweak symmetry breaking and an additional scalar field $Q$ with multiplicity $N_Q$ and mass $m_Q$. After imposing all theoretical and experimental constraints, we show that a strongly first order EWPT with detectable GW spectra can be realized for the two cases of light dilaton and PRHM. We also show the corresponding values of the relative enhancement of the cross section for the di-Higgs production process, which is related to the triple Higgs boson coupling. We obtain the region in which the GW spectrum can be observed by different future experiments such as LISA and DECIGO. We also show that the scenarios (1) and (2) can be discriminated by future GW observations and measurements of the di-Higgs productions at future colliders., Comment: 20 pages, 6 figures, version accepted by Journal of High Energy Physics

In this work, we investigate the viability of a light Higgs ($\eta$) scenario in the Georgi-Machacek (GM) model, where we consider all theoretical and experimental constraints such as the perturbativity, vacuum stability, unitarity, electroweak precision tests, the Higgs di-photon and undetermined decays and the Higgs total decay width. In addition, we consider more recent experimental bounds from the searches for doubly-charged Higgs bosons in the VBF channel $H_{5}^{++}\rightarrow W^{+}W^{+}$, Drell-Yan production of a neutral Higgs boson $pp\rightarrow H_{5}^{0}(\gamma\gamma)H_{5}^{+}$, and for the light scalars at LEP $e^{-}e^{+}\rightarrow Z\eta$, and at ATLAS and CMS in different final states such as $pp\rightarrow\eta\rightarrow2\gamma$ and $pp\rightarrow h\rightarrow\eta\eta\rightarrow4\gamma,2\mu2\tau,2\mu2b,2\tau2b$. By combining these bounds together, we found a parameter space region that is significant as the case of the SM-like Higgs to be the light CP-even eigenstate, and this part of the parameter space would be tightened by the coming analyses., Comment: 13 pages, 3 figures, version includes modifications due to the erratum in https://journals.aps.org/prd/abstract/10.1103/PhysRevD.108.019902

In this work, we present a scotogenic model, where the neutrino mass is generated at one-loop diagrams. The standard model (SM) is extended by three singlet Majorana fermions and two inert scalar doublets instead of one doublet as in the minimal scotogenic model. The model scalar sector includes two CP-even, two CP-odd and two charged scalars in addition to the Higgs. The dark matter (DM) candidate could be either the light Majorana fermion (Majorana DM), or the lightest among the CP-even and the CP-odd scalars (scalar DM). We show that the model accommodates both Majorana and scalar DM within a significant viable parameter space, while considering all the relevant theoretical and experimental constraints such as perturbativity, vacuum stability, unitarity, the di-photon Higgs decay, electroweak precision tests and lepton flavor violating constraints. In addition to the collider signatures predicted by the minimal scotogenic model, our model predicts some novel signatures that can be probed through some final states such as $8~jets+\slashed{E}_T$, $1\ell+4~jets+\slashed{E}_T$ and $4b+\slashed{E}_T$., Comment: 23 pages, 1 table & 6 figures. Published version

In this work, we investigate the parameter space of the Georgi-Machacek (GM) model, where we consider many theoretical and experimental constraints such as the perturbativity, vacuum stability, unitarity, electroweak precision tests, the Higgs di-photon decay, the Higgs total decay width and the LHC measurements of the signal strengths of the SM-like Higgs boson $h$ in addition to the constraints from doubly charged Higgs bosons and Drell-Yan di-photon production and the indirect constraint from the $b\to s$ transition processes. We investigate also the possibility that the electroweak vacuum could be destabilized by unwanted wrong minima that may violate the CP and/or the electric charge symmetries. We found that about 40 \% of the parameter space that fulfills the above mentioned constraints; are excluded by these unwanted minima. In addition, we found that the negative searches for a heavy resonance could exclude a significant part of the viable parameter space; and future searches could exclude more regions in the parameter space., Comment: More constraints are considered, 21 pages & 9 figures

In this work, we consider an extension of the Standard Model (SM) with an inert Higgs doublet and a real scalar singlet, in order to address problems around the origin of dark matter (DM). In this model, the lightest among the CP-odd and CP-even neutral inert components plays the role of a DM candidate, where the model parameters are subject to many theoretical and experimental constraints. These constraints include vacuum stability, perturbativity, LEP negative searches, electroweak precision tests, Higgs di-photon, Higgs invisible and Higgs undetermined decays, DM relic density and DM direct detection bounds. Using these constraints, we find that the allowed parameter space for these models is quite sizeable and could be explored in upcoming collider and astrophysical searches., Comment: 21 pages, 9 figures, to appear in Phys. Rev. D

In this paper, we investigate the mutual impact between the dark matter (DM) requirements and the scalar sector in the scale invariant (SI) scotogenic model. The model is motivated by the neutrino mass and DM within a classically SI framework. It is a SI generalization of the scotogenic model, where the standard model (SM) is extended by a real singlet, an inert scalar doublet and three Majorana singlet fermions, where the lightest one ($N_{1}$) could play the DM candidate role. In addition to the annihilation channels $N_{1}N_{1}\rightarrow\ell_{\alpha}\ell_{\beta},\nu_{\alpha}\bar{\nu}_{\beta}$, the DM can be annihilated via few s-channel processes into SM particles, that are mediated by the Higgs/dilaton. This allows the new Yukawa interactions, that are responsible for neutrino mass generation, to take small values and therefore avoid the mass degeneracy between the CP-even and CP-odd inert scalars unlike the case of the minimal scotogenic model. In contrast to many Majorana DM models, the DM in the SI-scotogenic model couples to the quarks at tree-level, and hence the constraint from the direct detection experiments is very important on the space parameter. The aim of this work is to investigate the correlation between the DM requirements and the scalar sector in this model., Comment: 20 pages, 5 figures and 1 table

In this work, we investigate the possibility of having scale invariant (SI) standard model (SM) extensions, where the light CP-even scalar matches the SM-like Higgs instead of being a light dilaton. After deriving the required conditions for this scenario, we show that the radiative corrections that give rise to the Higgs mass can trigger the scalar mixing to the experimentally allowed values. In addition, we discuss the constraints on the parameters space that makes the CP-even scalars properties in a good agreement with all the recent ATLAS and CMS measurements. We illustrate this scenario by considering the SI-scotogenic model as an example, while imposing all the theoretical and experimental constraints. We show that the model is viable and leads to possible modifications of the di-Higgs signatures at current/future with respect to the SM., Comment: 11 pages, 3 figures, accepted for publication in NPB

We investigate the phenomenology of an extension of the Standard Model (SM) by a non-abelian gauge group $SU(2)_{HS}$ where all SM particles are singlets under this gauge group, and a new scalar representation $\phi$ that is singlet under SM gauge group and doublet under $SU(2)_{HS}$. In this model, the dark matter (DM) candidates are the three mass degenerate dark photons $A_{i}$ $(i=1,2,3)$ of $SU(2)_{HS}$; and the hidden sector interacts with the (SM) particles through the Higgs portal interactions. Consequently, there will be a new CP-even scalar $\eta$ that could be either heavier or lighter than the SM-like Higgs. By taking into account all theoretical and experimental constraints such as perturbativity, unitarity, vacuum stability, non-SM Higgs decays, DM direct detection, DM relic density, we found viable DM is possible in the range from GeV to TeV. Within the viable parameters space, the both of the triple Higgs coupling and the di-Higgs production at LHC14 could be enhanced or reduced depending on the scalar mixing and the mass of the scalar particle $\eta$., Comment: 22 pages & 11 figures

In this letter, we propose an extension of the scotogenic model where singlet Majorana particle can be dark matter (DM) without the need of a highly suppressed scalar coupling of the order $O(10^{-10})$. For that, the SM is extended with three singlet Majorana fermions, an inert scalar doublet, and two (a complex and a real) singlet scalars, with a global $Z_{4}$ symmetry that is spontaneously broken into $Z_{2}$ at a scale higher than the electroweak one by the vev of the complex singlet scalar. In this setup, the smallness of neutrino mass is achieved via the cancellation between three diagrams a la scotogenic, a DM candidate that is viable for a large mass range; and the phenomenology is richer than the minimal scotogenic model., Comment: 12 pages, 4 figures & 2 tables. Matches published version

We report on the status of efforts to improve the reinterpretation of searches and measurements at the LHC in terms of models for new physics, in the context of the LHC Reinterpretation Forum. We detail current experimental offerings in direct searches for new particles, measurements, technical implementations and Open Data, and provide a set of recommendations for further improving the presentation of LHC results in order to better enable reinterpretation in the future. We also provide a brief description of existing software reinterpretation frameworks and recent global analyses of new physics that make use of the current data., Comment: 58 pages, minor revision following comments from SciPost referees

Compilation of papers presented by the JEM-EUSO Collaboration at the 36th International Cosmic Ray Conference (ICRC), held July 24 through August 1, 2019 in Madison, Wisconsin., Comment: links to the 24 papers published in arXiv

We study the phenomenology of scotogenic model in the case of Majorana Dark Matter (DM) candidate. This scenario gives important consequences since the parameter space of the model is almost unconstrained compared to the Inert Higgs Doublet Model (or the scotogenic model with scalar DM), and hence, offers new opportunities for discovery at future high energy collider, e.g. the HL-LHC. As an example, we focus on the production of the Standard Model (SM) Higgs boson in association with a pair of dark scalars. Owing to its clean signature, the $\gamma\gamma$ decay channel of the SM Higgs boson is investigated in great detail at both the HL-LHC (at $\sqrt{s}=14$ TeV) and the future FCC-hh (at $\sqrt{s}=100$ TeV). After revisiting the LHC constraints from run-II on the parameter space of the model, and selecting benchmark points satisfying all the theoretical and experimental constraints, we found that scalars with mass up to $140$ GeV ($160$ GeV) can be probed at the LHC (FCC-hh) with a $3$ ab$^{-1}$ of integrated luminosity assuming $5\%$ of uncertainty., Comment: 26 pages, 12 figures, and 5 tables. Title changed, discussion improved, and references added

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., Comment: 11 pages, 4 figures, published version matched

EUSO-Balloon is a pathfinder mission for the Extreme Universe Space Observatory onboard the Japanese Experiment Module (JEM-EUSO). It was launched on the moonless night of the 25$^{th}$ of August 2014 from Timmins, Canada. The flight ended successfully after maintaining the target altitude of 38 km for five hours. One part of the mission was a 2.5 hour underflight using a helicopter equipped with three UV light sources (LED, xenon flasher and laser) to perform an inflight calibration and examine the detectors capability to measure tracks moving at the speed of light. We describe the helicopter laser system and details of the underflight as well as how the laser tracks were recorded and found in the data. These are the first recorded laser tracks measured from a fluorescence detector looking down on the atmosphere. Finally, we present a first reconstruction of the direction of the laser tracks relative to the detector., Comment: 18 pages, 14 figures

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 $S S(\gamma)$, where we give different cuts and show the predicted distributions. We show also that using polarized beams could improve the statistical significance., Comment: 9 pages, 7 figures, 1 table. Talk given at "Les Rencontres de Physique de la Vall\'ee d'Aoste: Results and Perspectives in Particle Physics" 2017

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., Comment: 19 pages, 13 figures and 3 tables. Extended discussion on collider phenomenology of the model

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., Comment: 15 pages, 10 figures, 7 tables & matches the published version

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 $\ell_{\alpha}\rightarrow\ell_{\beta}\gamma$ and $\ell_{\alpha}\rightarrow3\ell_{\beta}$. We also investigate the possibility of probing these interactions, and hence the right-handed neutrino, at leptonic colliders through different final state signatures., Comment: 21 pages, 17 figures & 4 tables, matches published version

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 $\ell_{\alpha}^{\pm }\ell_{\beta}^{\pm}\ell_{\gamma}^{\mp}$ + $\slashed{E}_{T}$ where ${\alpha}$, ${\beta}$, ${\gamma}$= $e,\mu,\tau$, 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., Comment: Proceedings of Moriond EW & UT 2016 (4 pages, 4 figures)

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 $pp\rightarrow\ell_{\alpha}^{\pm}\ell_{\beta}^{\mp}$ +$\slashed E$ with $\ell_{\alpha}\ell_{\beta}=ee,e\mu,\mu\mu$ 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.., Comment: Moriond proceedings

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., Comment: 10 pages, 6 figures & 4 tables

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., Comment: 14 pages, 6 figures. v3 PRD version

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., Comment: 21 pages, 8 figures; v2 JHEP version

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 $\sigma(pp\rightarrow\tilde{s}\rightarrow\gamma\gamma)$ 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 $\tilde s$ which are potentially testable in upcoming LHC measurements., Comment: 29 pages, 6 figures, retitled, expanded to address dark matter & neutrino mass, matches journal version

A recent paper investigated minimal R$\nu$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$\nu$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., Comment: 13 pages v3 PLB version

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., Comment: 8 pages & 4 figures, published version

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 $h\rightarrow\gamma \gamma$ and, furthermore, we find that the electroweak phase transition becomes strongly first-order in large regions of parameter space., Comment: 20 pages, 6 figures & 1 table

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., Comment: 24 pages, 7 figures; v2 Published version

In this work, we report on recent analyses of a class of models that generate neutrino mass at the three-loop level. We argue that these models offer a viable solution to both the neutrino mass and dark matter problems, without being in conflict with experimental constraints from, e.g. lepton flavor violating processes and the muon anomalous magnetic moment. Furthermore, we describe observable experimental signals predicted by the models and show that they have common signatures that can be probed at both the LHC and ILC., Comment: 6 pages, 4 figures, 1 table, to appear in the proceedings of the 50th Rencontres de Moriond, Electroweak session, 2015

In this work, we report on recent analysis of three-loop models of neutrino mass with dark matter. We discuss in detail the model of Krauss-Nasri-Trodden (KNT) [1], showing that it offers a viable solution to the neutrino mass and dark matter problems, and describe observable experimental signals predicted by the model. Furthermore, we show that the KNT model belongs to a larger class of three-loop models that can differ from the KNT approach in interesting ways., Comment: 6 pages, 5 figures, talk at HPNP2015, Toyama, February 2015

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 $\mu\rightarrow e+\gamma$ searches, and predicts a charged scalar that can appear at the TeV scale, within reach of collider experiments., Comment: 9 pages, 3 figures; v2 minor correction to PLB version (results unchanged)

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 $h\to\gamma\gamma,\gamma Z$, 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., Comment: 17 page, 8 figures

In this work we investigate the sphaleron solution in a $SU(2)\times U(1)_X$ gauge theory, which also encompasses the Standard Model, with higher scalar representation(s) ($J^{(i)},X^{(i)}$). We show that the field profiles describing the sphaleron in higher scalar multiplet, have similar trends like the doublet case with respect to the radial distance. We compute the sphaleron energy and find that it scales linearly with the vacuum expectation value of the scalar field and its slope depends on the representation. We also investigate the effect of $U(1)$ gauge field and find that it is small for the physical value of the mixing angle, $\theta_{W}$ and resembles the case for the doublet. For higher representations, we show that the criterion for strong first order phase transition, $v_{c}/T_{c}>\eta$, is relaxed with respect to the doublet case, i.e. $\eta<1$., Comment: 20 pages, 5 figures & 1 table, published version