Two Higgs Doublet Models (2HDM) provide a simple framework for new physics models with an extended Higgs sector. The current LHC results, including both direct searches for additional non-Standard Model (SM) Higgs bosons, as well as precision measurements of the SM-like Higgs couplings, already provide strong constraints on the 2HDM parameter spaces. In this paper, we examine those constraints for the neutral scalars in the Type-I and Type-II 2HDM. In addition to the direct search channels with SM final states: $H/A \to f\bar f, VV, Vh, hh$, we study in particular the exotic decay channels of $H/A \to AZ/HZ$ once there is a mass hierarchy between the non-SM Higgses. We found that $H/A \to AZ/HZ$ channel has unique sensitivity to the alignment limit region which remains unconstrained by conventional searches and Higgs precision measurements. This mode also extends the reach at intermediate $\tanβ$ for heavy $m_A$ that are not covered by the other direct searches.
The $Z_3$ soft breaking in the I(2+1)HDM and its cosmological probes
Facultad de Ciencias Físico-Matemáticas, Benemérita Universidad Autónoma de Puebla（普埃布拉自治理工医科大学理学院）；Facultad de Ciencias de la Electrónica, Benemérita Universidad Autónoma de Puebla（普埃布拉自治理工大学电子科学学院）；Dual CP Institute of High Energy Physics（高能物理双CP研究所）；Facultad de Ciencias, Universidad de Colima（科利马大学理学院）；School of Physics and Astronomy, University of Southampton（南安普顿大学物理与天文学院）；Department of Physics and Astronomy, Uppsala University（乌普萨拉大学物理与天文系）；Division of Liberal-Arts, Kogakuin University（工机大学文理学部）；Department of Natural Science, International Christian University（国际基督教大学自然科学系）
We explore the possibility that the discrepancy in the observed anomalous magnetic moment of the muon $Δa _μ$ and the predicted relic abundance of Dark Matter by Planck data, can be explained in a lepto-philic 2-HDM augmented by a real SM singlet scalar of mass $\sim$ 10-80 GeV. We constrain the model from the observed Higgs Decay width at LHC, LEP searches for low mass exotic scalars and anomalous magnetic moment of an electron $Δa_e$. This constrained light singlet scalar serves as a portal for the fermionic Dark Matter, which contributes to the required relic density of the universe. A larg…
We introduce a 3-Higgs Doublet Model (3HDM) with two Inert (or dark) scalar doublets and an active Higgs one, hence termed I(2+1)HDM, in the presence of a discrete $Z_3$ symmetry acting upon the three doublet fields. We show that such a construct yields a Dark Matter (DM) sector with two mass-degenerate states of opposite CP parity, both of which contribute to DM dynamics, which we call \textit{Hermaphrodite DM}, distinguishable from a (single) complex DM candidate. We show that the relic density contributions of both states are equal, saturating the observed relic density compliant with (in)d…
Following the discovery of a Higgs boson, there has been renewed interest in the general 2-Higgs-Doublet Model (2HDM). A model with One Inert Doublet plus One Higgs Doublet (I(1+1)HDM), where one of the scalar doublets is "inert" (since it has no vacuum expectation value and does not couple to fermions) has an advantage over the 2HDM since it provides a good Dark Matter (DM) candidate, namely the lightest inert scalar. Motivated by the existence of three fermion families, here we consider a model with two scalar doublets plus one Higgs doublet (I(2+1)HDM), where the two scalar doublets are ine…
A $ Z_3 $ symmetric 3-Higgs Doublet Model (3HDM) with two inert doublets and one active doublet (that plays the role of the Higgs doublet), the so-called I(2+1)HDM, is studied. We discuss the behaviour of this 3HDM realisation when one allows for a $ Z_3 $ soft breaking term. Such a symmetry enables the presence of a two-component Dark Matter (DM) scenario in the form of "Hermaphrodite DM", where the two inert candidates have opposite CP parity and are protected by this discrete symmetry from decaying into Standard Model (SM) particles. Furthermore, the two DM states are potentially distinguis…
We make a phenomenological study of a model with two inert doublets plus one Higgs doublet (I(2+1)HDM) which is symmetric under a Z$_2$ group, preserved after Electro-Weak Symmetry Breaking (EWSB) by the vacuum alignment $(0,0,v)$. This model may be regarded as an extension to the model with one inert doublet plus one Higgs doublet (I(1+1)HDM), by the addition of an extra inert scalar doublet. The neutral fields from the two inert doublets provide a viable Dark Matter (DM) candidate which is stabilised by the conserved $Z_2$ symmetry. We study the new Higgs decay channels offered by the scalar…
We demonstrate that certain weighted moments of $t\anti t \h$ production can provide a determination of the CP nature of a light neutral Higgs boson produced and detected in this mode at the CERN LHC.
Under the hypothesis that the MSSM neutralino accounts for the observed dark matter density, we investigate how light this particle is still allowed to be after the latest LHC data. In particular, we discuss the impact of searches for events with multiple taus and missing transverse momentum, which are a generic prediction of the light neutralino scenario.
We study the prospects of probing large extra dimension model at the LHC through neutral triple gauge boson production processes. In theories with extra dimensions these processes result from the exchange of a tower of massive graviton modes between the SM particles. We consider γγγ, γγZ, γZ Z and ZZZ production processes, and present our results for various kinematic distributions at the LHC for \sqrt{S}=14 TeV.
We address the question how light the lightest MSSM neutralino can be as dark matter candidate in a scenario where all supersymmetric scalar particles are heavy. The hypothesis that the neutralino accounts for the observed dark matter density sets strong requirements on the supersymmetric spectrum, thus providing an handle for collider tests. In particular for a lightest neutralino below 100 GeV the relic density constraint translates into an upper bound on the Higgsino mass parameter $μ$ in case all supersymmetric scalar particles are heavy. One can define a simplified model that highlights o…
We present the discovery prospects for a Z' resonance and some expected results for Z' diagnostic measurements at the LHC. The discovery reach is highly dependent on the energy and luminosities that may be attained at the LHC, and a number of energy and integrated luminosity scenarios are presented. In addition, the use of third generation quark final states for distinguishing between models and for measuring a forward-backward asymmetry is explored.
Flavour-changing neutral-current interactions of the top quark can be searched for in top-quark pair production with one top quark decaying to an up-type quark and a neutral boson, and they can be searched for in the single production of a top quark in association with such a boson. Both processes interfere if an additional up-type quark is produced in the case of single production. The impact of these interference effects on searches for flavour-changing neutral currents at the LHC is studied for the case where the neutral boson is a photon or a $Z$ boson. Interference effects are found to be…
In this paper, triple neutral electroweak gauge boson production processes, viz. γγγ, γγZ, γZZ and ZZZ productions merged to 1-jet have been studied at the leading order in QCD in the context of Randall-Sundrum model at the LHC with center of mass energy \sqrt{S}=13 TeV. Decay of Z bosons into lepton-pairs has been considered. We present a selection of kinematical distributions matched to parton shower and show their deviation from the SM results as a result of the RS model. The uncertainties as a result of the factorization and renormalization scales are also presented.
The search for the production of weakly-interacting SUSY particles at the LHC is crucial for testing supersymmetry in relation to dark matter. Decays of neutralinos into Higgs bosons occur over some significant part of the SUSY parameter space and represent the most important source of $h$ boson production in SUSY decay chains in the MSSM. We study h production in neutralino decays using scans of the phenomenological MSSM. Whilst in constrained MSSM scenarios the decay chi^0_2 -> h chi^0_1 is the dominant channel, this does not hold in more general MSSM scenarios. On the other hand, the chi^0_…
The reconstruction of the Higgs potential in the Standard Model or supersymmetric theories demands the measurement of the trilinear Higgs couplings. These couplings affect the multiple production of Higgs bosons at high energy colliders. We present a systematic overview of the cross sections for the production of pairs of (light) neutral Higgs bosons at the LHC. The analysis is carried out for the Standard Model and its minimal supersymmetric extension.
We update our earlier results regarding detection of $gg\to b\anti b h\to 4b$ ($h=h^0,H^0,A^0$) to incorporate the very high $b$-tagging efficiencies and purities that are now anticipated at the LHC. New results for the Tev$^*$ are given, and indicate substantial potential for these modes. The complementarity of the $H^0\to h^0h^0 \to 4b$ final state mode is illustrated for the LHC. The latest radiative corrections to the Higgs sector are incorporated.
The model independent bounds on new neutral vector resonances masses, couplings and widths presented at arxiv:1112.0316 are updated with an integrated luminosity of L=4.7 fb^-1 from ATLAS and L=4.6 fb^-1 from CMS. These exclusion limits correspond to the most stringent existing bounds on the production of new neutral spin-1 resonances that decay to electroweak gauge boson pairs and that are associated to the electroweak symmetry breaking sector in several extensions of the Standard Model.
We analyze the effects of the s-channel Higgs bosons exchange on the charginos and neutralinos-pair production in proton-proton collision at the CERN Large Hadron Collider (LHC) in the following channels: $pp \to \Cha^+\Cha^-/\Neu^0\Neu^0 + X$, within the minimal supersymmetric standard model (MSSM). Assuming the usual GUT relation between $M_1$ and $M_2$ at the weak scale, we found that substantial enhancement can be obtained through s-channel Higgs bosons exchange in the mixed regime where $M_2 \sim |μ|$ with moderate to large $\tanβ$ at the resonance of the heavy Higgs bosons. By Combining …
The spectrum of supersymmetric theories with R-parity violation are much more weakly constrained than that of supersymmetric theories with a stable neutralino. We investigate the signatures of supersymmetry at the LHCb experiment in the region of parameter space where the neutralino decay leaves a displaced vertex. We find sensitivity to squark production up to squark masses of order 1 TeV. We note that if the Higgs decays to neutralinos in this scenario, LHCb should see the lightest Higgs boson before ATLAS and CMS.
It was shown in a previous study that a lightest neutralino with mass below 30 GeV was severely constrained in the minimal supersymmetric standard model (MSSM), unless it annihilates via a light stau and thus yields the observed dark matter abundance. In such a scenario, while the stau is the next-to-lightest supersymmetric particle (NLSP), the charginos and the other neutralinos as well as sleptons of the first two families are also likely to be not too far above the mass bounds laid down by the Large Electron Positron (LEP) collider. As the branching ratios of decays of the charginos and the…
A U(1)' or Z' is generic in many scenarios of physics beyond the Standard Model, such as string theory compactifications, GUTs, extra-dimensions, compositeness, dynamical electroweak symmetry breaking, dark-sector models, etc. We study the potential of probing a TeV-scale Z' with electroweak couplings in future experiments. In particular, we focus on two scenarios: (1) If a Z' is discovered at the LHC, what is the potential of measuring its mass and width and to distinguish between benchmark models utilizing various observables, especially asymmetries, at a high luminosity LHC and the ILC. (2)…
The two-Higgs-doublet model contains extra Higgs bosons, with mass ranges spanning from several hundred GeV to about 1 TeV. We study the possible experimental searches for the neutral Higgs bosons of $A$ and $H$ at the future high-luminosity LHC runs. Besides of the conventional search modes that are inspired by the supersymmetric models, we discuss two search modes which were not quite addressed previously. They are the decay modes of $A\to hZ$ and $A/H \to t \bar t$. Thanks to the technique of tagging boosted objects of SM-like Higgs bosons and top quarks, we show the improved mass reaches f…
The prospects of searching for the flavor changing neutral current effect in the decay of $t\to H c, H\to ττ$ are investigated with the simulated $p-p$ collision data for the ATLAS detector at the LHC, where the Higgs mass is assumed to be 125~GeV. A fit based on the constraints from the Higgs mass and the tau decay kinematics is performed for each event, which improves significantly the Higgs and top mass reconstruction and helps the signal-background separation. Boosted Decision Trees discriminants are developed to achieve an optimal sensitivity of searching for the FCNC signal. An expected …
New Neutral Gauge Bosons, Z' 's, are predicted by many models of physics beyond the Standard Electroweak Theory. It is possible that a Z' would be discovered early in the Large Hadron Collider program. The next step would be to measure its properties to identify the underlying theory that gave rise to the Z'. Heavy quarks have the unique property that they can be identified in the final states. In this letter we demonstrate that measuring Z' decays to b- and t-quark final states can act as an effective means of discriminating between models with extra gauge bosons.
Several extensions of the Standard Model predict the existence of new neutral spin-1 resonances associated to the electroweak symmetry breaking sector. Using the data from ATLAS (with integrated luminosity of L=1.02 fb^{-1}) and CMS (with integrated luminosity of L=1.55 fb^{-1}) on the production of W+W- pairs through the process pp -> l^+ l^{\prime -} \sla{E}_T, we place model independent bounds on these new vector resonances masses, couplings and widths. Our analyses show that the present data excludes new neutral vector resonances with masses up to 1-2.3 TeV depending on their couplings and…
Interest in searches for heavy neutral leptons (HNLs) at the LHC has increased considerably in the past few years. In the minimal scenario, HNLs are produced and decay via their mixing with active neutrinos in the Standard Model (SM) spectrum. However, many SM extensions with HNLs have been discussed in the literature, which sometimes change expectations for LHC sensitivities drastically. In the $N_R$SMEFT, one extends the SM effective field theory with operators including SM singlet fermions, which allows to study HNL phenomenology in a "model independent" way. In this paper, we study the sen…
We study the implications of LHC searches on SUSY particle spectra using flat scans of the 19-parameter pMSSM phase space. We apply constraints from flavour physics, g_mu-2, dark matter and earlier LEP and Tevatron searches. The sensitivity of the LHC SUSY searches with jets, leptons and missing energy is assessed by reproducing with fast simulation the recent CMS analyses after validation on benchmark points. We present results in terms of the fraction of pMSSM points compatible with all the constraints which are excluded by the LHC searches with 1 fb^{-1} and 15 fb^{-1} as a function of the …
We study the constraints on $t\to u$ flavor changing neutral Higgs (FCNH) coupling, and how it may be explored further at the Large Hadron Collider (LHC). In the general two Higgs doublet model, such transitions can be induced by a nonzero $ρ_{tu}$ Yukawa coupling. We show that such couplings can be constrained by existing searches at the LHC for $m_H$, $m_A$ and, $m_{H^+}$ in the sub-TeV range, where $H$, $A$ and $H^+$ are the exotic $CP$-even, $CP$-odd and charged scalars. We find that a dedicated $ug\to t H/tA \to t t \bar u$ search can probe the available parameter space of $ρ_{tu}$ down t…
We study SUSY signatures at the 7, 8 and 14 TeV LHC employing the 19-parameter, R-Parity conserving p(henomenological)MSSM, in the scenario with a neutralino LSP. Our results were obtained via a fast Monte Carlo simulation of the ATLAS SUSY analysis suite. The flexibility of this framework allows us to study a wide variety of SUSY phenomena simultaneously and to probe for weak spots in existing SUSY search analyses. We determine the ranges of the sparticle masses that are either disfavored or allowed after the searches with the 7 and 8 TeV data sets are combined. We find that natural SUSY mode…
We have analyzed the prospect of detecting a higgs signal in mSUGRA/CMSSM based Supersymmetric(SUSY) model via chargino-neutralino($\CH_1\N0_2$) production at 8 TeV and 14 TeV LHC energy. The signal is studied in the channel with $\ell + b \bar b + \PMET$ following the decays, $\CH_1 \to W^\pm \N0_1$, $\N0_2 \to \N0_1 h$ and $h \to b \bar b$. In this analysis reconstruction of the higgs mass out of two b-jets plays a very crucial role in determining the signal to background ratio. We follow two techniques to reconstruct higgs mass: (A) using two identified b-jets, (B) using jet substructure te…
We investigate signatures induced by a very light pseudoscalar Higgs in neutralino decays in the Next-to-Minimal Supersymmetric Standard Model (NMSSM) and determine their observability at the LHC. We concentrate on scenarios which feature two light scalar Higgs bosons (one of them is SM-like with a mass of 125 GeV and a singlet-like lighter one) with a very light (singlet-like) pseudoscalar Higgs in the mass range 2m_tau < m_a1 < 2m_b. We consider neutralino-chargino pair production and the subsequent decay X_{2,3}-> X_1 a1, which leads to topologies involving multi-leptons and missing transve…
Natural models of supersymmetry with a gravitino LSP provide distinctive signatures at the LHC. For a neutralino NLSP, sparticles can decay to two high energy photons plus missing energy. We use the ATLAS diphoton search with 4.8 fb^{-1} of data to place limits in both the stop-gluino and neutralino-chargino mass planes for this scenario. If the neutralino is heavier than 50 GeV, the lightest stop must be heavier than 580 GeV, the gluino heavier than 1100 GeV and charginos must be heavier than approximately 300-470 GeV. This provides the first nontrivial constraints in natural gauge mediation …
This article summarizes a talk given at Higgs Hunting 2014 on projections of the sensitivity of the ATLAS and CMS experiments to beyond Standard Model Higgs physics at the High Luminosity Large Hadron Collider. We describe results on vector boson scattering, searches for additional neutral Higgs bosons in two Higgs doublet models and flavour changing neutral current top decays.
We perform a comprehensive study of The Higgs potential of the two Higgs doublet model extended by a real triplet scalar field $Δ$. This model, dubbed $2\mathcal{HDM+T}$, has a rich Higgs spectrum consisting of three CP-even Higgs $h_{1,2,3}$, one CP-odd $A_0$ and two pairs of charged Higgs $H^\pm_{1,2}$. First, we determine the perturbative unitarity constraints and a set of non trivial conditions for the boundedness from below (BFB). Then we derive the Veltman conditions by considering the quadratic divergencies of Higgs boson self energies in $2\mathcal{HDM+T}$. We find that the parameter s…
We study the potential to use measurements of extra neutral gauge bosons (Z') properties in pp collisions at the Large Hadron Collider to unravel the underlying physics. We focus on the usefulness of third generation final states (tau, b, t) in distinguishing between models with non-universal Z'-fermion couplings. We present an update of discovery limits of Z's including the 2010-2011 LHC run and include models with non-universal couplings. We show how ratios of sigma(pp -> Z' -> ttbar), sigma(pp -> Z' -> bbbar), and sigma(pp -> Z' -> tau^+tau^-) to sigma(pp -> Z' -> mu^+mu^-) can be used to d…
An overview of current experimental bounds on $CPT$ violation in neutral meson mixing is given. New values for the $CPT$ asymmetry in the $B^0$ and $B_s^0$ systems are deduced from published BaBar, Belle and LHCb results. With dedicated analyses, LHCb will be able to further improve the bounds on $CPT$ violation in the $D^0$, $B^0$ and $B_s^0$ systems. Since $CPT$ violation implies violation of Lorentz invariance in an interacting local quantum field theory, the observed $CPT$ asymmetry will exhibit sidereal- and boost-dependent variations. Such $CPT$-violating and Lorentz-violating effects ar…
We consider chargino-neutralino production, $\tildeχ_2^0 \tildeχ_1^\pm \to (h \tildeχ_1^0)(W^\pm \tildeχ_1^0)$, which results in Higgs boson final states that subsequently decay (inclusively) to leptons (either $h\rightarrow τ^+τ^-$ or $h\rightarrow W^+W^- \to (e^+e^-, μ^+μ^-, τ^+τ^-)+E_T^\mathrm{miss}$). Such channels are dominant in large regions of the allowed supersymmetric parameter space for many concrete supersymmetric models. The existence of leptons allows for good control over the backgrounds, rendering this channel competitive to the conventional $h\rightarrow b\bar{b}$ channel that…
In Higgsless models, new vector resonances appear to restore the unitarity of the W_L W_L scattering amplitude without the Higgs boson. In the ideal delocalized three site Higgsless model, one of large prodcution cross section of the neutral vector resonance (Z') at the Large Hadron Collider is the W-associated production, pp \to Z'W \to WWW. Although the dileptonic decay channnel, lνl'ν'jj, is experimentally clean to search for the Z' signals, it is difficult to reconstruct the Z' invariant mass due to the two neutrinos in the final state. We study collider signatures of Z' using the M_{T2}-A…
A complete list of operators contributing at the lowest order to Quartic Neutral Gauge Boson Couplings involving photons and Z-bosons, is presented. We show that, for the couplings we consider, the lowest order contribution is from dimension 8 operators in the case when a light Higgs is present and from dimension 6 operators in the higgsless case where electroweak symmetry is non-linearly realized. We also show that these operators are generated by exchange of the Kaluza-Klein partners of the graviton in extra-dimensional models. We then explore the possibility of probing these couplings in th…
We examine the parameter space of the purely phenomenological minimal super- symmetric standard model (MSSM), without assuming any supersymmetry breaking scheme. We find that a large region of the parameter space can indeed yield the lightest neutral Higgs mass around 125 GeV, as suggested by the recent ATLAS data, and also lead to event rates around, or slightly higher than, the standard model expectation in the two-photon and four-lepton channels. Using a lightest neutralino that is considerably lighter than the Higgs, we find that the 'invisible' decay of the Higgs into a pair of neutralino…
We study the possibility of explaining the recently reported 750 GeV di-photon excess at LHC within the framework of a left-right symmetric model. The 750 GeV neutral scalar in the model is dominantly an admixture of neutral components of scalar bidoublets with a tiny fraction of neutral scalar triplet. Incorporating $SU(2)$ septuplet scalar pairs into the model, we enhance the partial decay width of the 750 GeV neutral scalar into di-photons through charged septuplet components in loop while keeping the neutral septuplet components as subdominant dark matter candidates. The model also predict…
The "$μ$ from $ν$" supersymmetric standard model ($μν$SSM) can accommodate the newly discovered Higgs-like scalar boson with a mass around 125 GeV. This model provides a solution to the $μ$-problem and simultaneously reproduces correct neutrino physics by the simple use of right-handed neutrino superfields. These new superfields together with the introduced $R$-parity violation can produce novel and characteristic signatures of the $μν$SSM at the LHC. We explore the signatures produced through two-body Higgs decays into the new states, provided that these states lie below in the mass spectrum.…
The model of heavy neutral leptons (HNLs) is one of the well-motivated models beyond the standard model (BSM) from both theoretical and phenomenological point of views. It is an indispensable ingredient to explain the puzzle of tiny neutrino masses and the origin of the matter-antimatter asymmetry in our Universe, based on the models in which the simplest Type-I seesaw mechanism can be embedded. The HNL with a mass up to the electroweak scale is an attractive scenario which can be readily tested in present or near-future experiments including the LHC. In this work, we study the decay rates of …
Flavour changing neutral scalar interactions are a standard feature of generic multi Higgs models. These are constrained by mixing in the neutral meson systems. We consider situations where there are natural cancellations in such contributions. In particular, when the spin 0 particle has both scalar and pseudoscalar couplings, one may have a self-cancellation. We illustrate one such partial cancellation with BGL models. We also inquire whether the flavour changing quark interactions can lead to new production mechanisms for a neutral scalar at LHC.
The cross section prediction for the production of the lightest neutral Higgs boson in association with a high-p_T hadronic jet is presented in the framework of the minimal supersymmetric standard model (MSSM) and compared to the SM case. Prospects for the CERN Large Hadron Collider (LHC) are discussed.
Multiple production of Higgs particles is essential to study Higgs self-couplings at future high-energy colliders. In this paper we calculated the resonance contributions to the production of three lightest neutral supersymmetric Higgs bosons in gluon fusion at LHC. The cross sections due to trilinear Higgs couplings is sizeable but the measurement of the quartic coupling hhhH(h) seems to be impossible.
The phenomenology of neutral Higgs bosons from non--SUSY, extended Higgs sectors is studied in the context of the LHC, with particular attention given to the case of a fermiophobic Higgs. It is found that enhanced branching ratios to $γγ$ and $τ^+τ^-$ are possible and can provide clear signatures, while detection of a fermiophobic Higgs will be problematic beyond a mass of 130 GeV.
We consider the experimental data on neutral Kstar-meson production on nucleon and nuclear targets. The Quark-Gluon String Model quantitatively describes the inclusive density in the midrapidity region, as well as the initial energy and A dependences of the produced Kstar-mesons.
The topcolor-assisted technicolor (TC2) model predicts a number of neutral scalars like the top-pion ($π^0_t$) and the top-Higgs ($h^0_t$). These scalars have flavor-changing neutral-current (FCNC) top quark couplings, among which the top-charm transition couplings may be sizable. Such FCNC couplings induce single top productions associated with a neutral scalar at the CERN Large Hadron Collider (LHC) through the parton processes $cg \to t π_t^0$ and $cg \to t h_t^0$. In this note we examine these productions and find their production rates can exceed the $3σ$ sensitivity of the LHC in a large…
The inclusion of heavy neutral leptons to the Standard Model particle content could provide solutions to many open questions in particle physics and cosmology. The modification of the charged and neutral currents from active-sterile mixing of neutral leptons can provide novel signatures in Standard Model processes. We revisit the displaced vertex signature that could occur in collisions at the LHC via the decay of heavy neutral leptons with masses of a few GeV emphasizing the implications of flavor, kinematics, inclusive production and number of these extra neutral fermions. We study in partic…
We revisit the phenomenology of the Constrained MSSM with right-handed neutrinos (CMSSMRN). A supersymmetric seesaw mechanism, generating neutrino masses and sizable lepton flavour violating (LFV) entries is assumed to be operative. In this scheme, we study the complementarity between the `observable ranges' of various paths leading to the possible discovery of low energy SUSY: the reach of the Cern Large Hadron Collider (LHC), the quest for neutralino dark matter signals and indirect searches through LFV processes. Within the regions of the CMSSMRN parameter space compatible with all cosmo-ph…
Long-lived light particles (LLLPs) appear in many extensions of the standard model. LLLPs are usually motivated by the observed small neutrino masses, by dark matter or both. Typical examples for fermionic LLLPs (a.k.a. heavy neutral fermions, HNFs) are sterile neutrinos or the lightest neutralino in R-parity violating supersymmetry. The high luminosity LHC is expected to deliver up to 3/ab of data. Searches for LLLPs in dedicated experiments at the LHC could then probe the parameter space of LLLP models with unprecedented sensitivity. Here, we compare the prospects of several recent experimen…
In the framework of the left-right twin Higgs model, we study pair production of the neutral Higgs bosons at the International Linear Collider ($ILC$) and the $CERN$ $LHC$. We find that the production cross section of the process $e^{+}e^{-}\to ϕ^{0}h$ are at the level of several tens $fb$ at the $ILC$, the production cross section of the $ϕ^{0}ϕ^{0}$ pair and $ϕ^{0}h$ pair are at the level of several hundreds $fb$ at the $LHC$. As long as the neutral Higgs boson $ϕ^{0}$ is not too heavy, we conclude that its pair production might be used to test for the left-right twin Higgs model at the $LHC…
We study the signature of $H^\pm$ decay into $h^0W$ at the LHC in SUSY models. It has only marginal viability in the MSSM. But in the singlet extensions like the NMSSM one can have a spectacular signature for $H^\pm$ decay into $(h^0,A^0)W$ over a significant domain of parameter space.
We study the possibility of discovering neutral scalar Higgs bosons in the $U(1)'$-extended supersymmetric standard model (USSM) at the CERN Large Hadron Collider (LHC), by examining their productions via the exotic quark loop in the gluon fusion process at leading order. It is possible in some parameter region that the neutral scalar Higgs bosons may have stronger couplings with the exotic quarks than with top quark. In this case, the exotic quarks may contribute more significantly than top quark in productions of the neutral scalar Higgs bosons in the gluon fusion process. We find that there…
