We analyzed the triple Higgs boson self-coupling at future $e^{+}e^{-}$ colliders energies, with the reactions $e^{+}e^{-}\to b \bar b HH, t \bar t HH$. We evaluate the total cross-sections for both $b\bar bHH$ and $t\bar tHH$, and calculate the total number of events considering the complete set of Feynman diagrams at tree-level. We vary the triple coupling $κλ_{3H}$ within the range $κ=-1$ and +2. The numerical computation is done for the energies expected to be available at a possible Future Linear $e^{+}e^{-}$ Collider with a center-of-mass energy $800, 1000, 1500$ $GeV$ and a luminosity 1000 $fb^{-1}$. Our analysis is also extended to a center-of-mass energy 3 $TeV$ and luminosities of 1000 $fb^{-1}$ and 5000 $fb^{-1}$. We found that for the process $e^{+}e^{-}\to b \bar b HH$, the complete calculation differs only by 3% from the approximate calculation $e^{+}e^{-}\to ZHH(Z\to b\bar b)$, while for the process $e^{+}e^{-}\to t \bar tHH$, the expected number of events, considering the decay products of both $t$ and $H$, is not enough to obtain an accurate determination of the triple Higgs boson self-coupling.
Supersymmetric scenarios with a very weakly interacting lightest superpartner (LSP) - like the gravitino or axino - naturally give rise to a long-lived next-to-LSP (NLSP). If the NLSP is a charged slepton it leaves a very distinct signature in a collider experiment. At the ILC/CLIC it will be possible to capture a significant fraction of the produced charged sleptons and observe their decays. These decays potentially reveal the nature of the LSP and thus provide a unique possibility to measure the properties of a very weakly interacting LSP which otherwise is most likely hidden from any other …
The precision measurements of Higgs boson observables will be critical in the interpretation of the dynamics responsible for electroweak symmetry breaking. The capabilities of the ILC and CLIC for precision Higgs studies are well documented. In this talk, a theoretical framework is presented for interpreting phenomena that can arise in the two-Higgs-doublet model (2HDM). By imposing no constraints on the most general set of 2HDM parameters, the resulting formalism correctly identifies the physical 2HDM observables, which can be determined by model-independent experimental analyses.
We review the MasterCode fits of several incarnations of the Minimal Supersymmetric Standard Model (MSSM). These include the GUT models based on mAMSB and SU(5), sub-GUT models as well as a model defined at low energies with 11 free parameters, the pMSSM11. The fit combines consistently measurements of Higgs boson properties, searches for additional Higgs bosons and supersymmetric (SUSY) particles, low-energy and flavor experiments as well as Dark Matter (DM) measurements. We predict the preferred SUSY mass spectra in these models and analyze the discovery potential of future e+e- colliders su…
We present a detailed study of the anomalous single fourth generation $t'$ quark production within the dominant Standard Model(SM) decay modes at future $e^+e^-$ colliders. We calculate the signal and background cross sections in the mass range 300-800 GeV. We also discuss the limits of $t'qγ$ and $t'qZ$ ($q=u,c$) anomalous couplings as well as values of attainable integrated luminosity for 3$σ$ observation limit.
In this work, the production processes of heavy neutral scalar and pseudo scalar associated with standard model gauge boson $Z_L$ at future $e^{+}e^{-}$ colliders (ILC and CLIC) are examined. The total and differential cross sections are calculated for the processes in the context of the littlest Higgs model. Also dependence of production processes to littlest Higgs model parameters in the range of compatibility with electroweak precision measurements and decays to lepton flavor violating final states are analyzed. We have found that both heavy scalar and pseudoscalar will be produced in $e^+e…
We study the prospects of the B-L model with an additional $Z'$ boson to be a Higgs boson factory at high-energy and high-luminosity linear electron positron colliders, such as the ILC and CLIC, through the Higgs-strahlung process $e^{+}e^{-}\rightarrow (Z, Z') \to Zh$, including both the resonant and non-resonant effects. We evaluate the total cross section of $Zh$ and we calculate the total number of events for integrated luminosities of 500-2000\hspace{0.8mm}$fb^{-1}$ and center of mass energies between 500 and 3000\hspace{0.8mm}$GeV$. We find that the total number of expected $Zh$ events c…
We investigate the dipole moments of the tau- neutrino at high-energy and high luminosity at linear electron positron colliders, such as CLIC or ILC through the analysis of the reaction $e^{+}\, e^{-}\rightarrow ν\, \bar ν\,γ$ in the framework of the $SU(4)_L \times U(1)_X$ model. The limits on dipole moment were obtained for integrated luminosity of $\cal{L}$= 500-2000\, fb$^{-1}$ and center of mass between 0.5 and 3.0 TeV. The estimated limits for the tau-neutrino magnetic and electric dipole moments are improved by 2-3 orders of magnitude and complement previous studies on the dipole moment…
The International Linear Collider (ILC) and the Compact Linear Collider (CLIC) are the two options for a future high-energy, high-luminosity linear electron-positron collider. Both are expected to be built in stages, optimised for their physics potential. The main goals are the precision measurements of Higgs-boson and top-quark properties as well as direct and indirect searches for new physics Beyond Standard Model. In my talk I will review some of the latest results from both ILC and CLIC demonstrating their physics potential, pointing to similarities and complementarity of both projects.
In this work we study the sensitivity on the anomalous magnetic and electric dipole moments of the tau-neutrino in the framework of the $SU(2)_L\times U(1)_Y\times U(1)_{B-L}$ electroweak model at future $e^+e^-$ linear colliders as the ILC and CLIC. For our study we consider the process $e^{+}e^{-}\rightarrow ( Z, Z', γ) \to ν_τ\bar ν_τγ$. For center-of-mass energies of $\sqrt{s}=1000-3000\hspace{0.8mm}GeV$ and integrated luminosities of ${\cal L}=500-2000\hspace{0.8mm}fb^{-1}$, we derive $95 \% \hspace{1mm}$ C.L. limits on the dipole moments $|μ_{ν_τ}(μ_B)| \leq 6.28 \times 10^{-9}$ and $|d_…
We study pair-production as well as the triple self-couplings of the neutral Higgs bosons of the Minimal Supersymmetric Standard Model (MSSM) at the Future International Linear $e^{+}e^{-}$ Collider (ILC) and Compact Linear Collider (CLIC). The analysis is based on the reactions $e^{+}e^{-}\to b \bar b h_ih_i, t \bar t h_ih_i$ with $h_i=h, H, A$. We evaluate the total cross-section for both $b\bar bh_ih_i$, $t\bar th_ih_i$ and calculate the total number of events considering the complete set of Feynman diagrams at tree-level. We vary the triple couplings $κλ_{hhh}$, $κλ_{Hhh}$, $κλ_{hAA}$, $κλ…
For the search for electroweak particles in the Minimal Supersymmetric Standard Model (MSSM) as well as for future precision analyses of these particles an accurate knowledge of their production and decay properties is mandatory. We review the evaluation of the cross sections for the chargino, neutralino and scalar lepton production at e+e- colliders in the MSSM with complex parameters (cMSSM). The evaluation is based on a full one-loop calculation of the various production mechanisms, including soft and hard photon radiation. The dependence of the chargino/neutralino/slepton cross sections on…
In this work we study the potential of the processes $e^+e^- \to e^+γ^* e^- \to e^+τ\barν_τν_e $ and $e^+e^- \to e^+γ^* γ^* e^- \to e^+ν_τ\barν_τe^- $ at a future high-energy and high-luminosity linear electron positron collider, such as the ILC and CLIC to study the sensibility on the anomalous magnetic and electric dipole moments of the tau-neutrino. For integrated luminosity of 590\hspace{1mm}$fb^{-1}$ and center-of-mass energy of 3\hspace{1mm}$TeV$, we derive $95 \% \hspace{1mm}C. L.$ limits on the dipole moments: $μ_{ν_τ}\leq 1.44 \times 10^{-6}μ_B$ and $d_{ν_τ}\leq 2.78 \times 10^{-17}\h…
We review results from our frequentist analysis of the parameter space of the pMSSM10, in which the following 10 soft SUSY-breaking parameters are specified independently at the mean scalar top mass scale Msusy = \sqrt{M_stop1 M_stop2}: the gaugino masses M_{1,2,3}, the 1st-and 2nd-generation squark masses M_squ1 = M_squ2, the third-generation squark mass M_squ3, a common slepton mass M_slep and a common trilinear mixing parameter A, the Higgs mixing parameter mu, the pseudoscalar Higgs mass M_A and tan beta, the ratio of the two Higgs vacuum expectation values. We implemented the LHC searches…
We obtain bounds for the mass of the extra neutral gauge boson, ${Z^\prime}$, predicted by two versions of ${SU (3)_C \times SU (3)_L \times U (1)_X}$ model, namely one corresponding to its minimal version and another where the neutrinos are allowed to have right-handed projection. We explore $\sqrt s$ from 0.5 TeV to 5 TeV region, that will be accessible in next linear colliders (ILC and CLIC). We used the process $e^+ + e^- \longrightarrow f^+ + f^-$, with $f=μ$, $c$ and $b$ to obtain the energy dependent lower bounds for $M_{Z^\prime}$, within 95% C.L., by performing a $χ^{2}$ fit of the di…
Quasi-elastic scattering of the vector bosons W and Z is a sensitive probe of the details of electroweak symmetry breaking, and a key process at future lepton colliders. We discuss the limitations of a model-independent effective-theory approach and describe the extension to a class of Simplified Models that is applicable to all energies in a quantitative way, and enables realistic Monte-Carlo simulations. The framework has been implemented in the Monte-Carlo event generator WHIZARD.
Higgs triplet fields are introduced various new physics models such as the type-II seesaw model, the left-right symmetric model and so on. The vertex of a charged Higgs boson and weak gauge bosons, $H^\pm W^\mp Z$, appears at the tree level in these models. The magnitude of this vertex is proportional to the vacuum expectation value (VEV) of Higgs triplet fields. We discuss the possibility of measuring this vertex at the ILC and study how precisely determine the VEV of the triplet field.
In this study we investigated indirect manifestations of color octet electron at the next generation linear colliders: International Linear Collider (ILC) and Compact Linear Collider (CLIC). Namely, production of two gluons via color octet electron exchange is considered. Signal and background analysis have been performed taking into account initial state radiation and beamstrahlung. We show that color octet electron (e_(8)) manifestation will be seen upto M(e_(8))=1.75 TeV and 1.70 TeV at ILC and CLIC with sqrt(s)=0.5 TeV, respectively. CLIC with sqrt(s)=3 TeV will be sensitive upto M(e_(8))=…
In this paper, we present the precision predictions for three photon production in the standard model (SM) at the ILC including the full next-to-leading (NLO) electroweak (EW) corrections, high order initial state radiation (h.o.ISR) contributions and beamstrahlung effects. We present the LO and the NLO EW+h.o.ISR+beamstrahlung corrected total cross sections for various colliding energy when $\sqrt s \ge 200 {\rm GeV}$ and the kinematic distributions of final photons with $\sqrt s = 500 {\rm GeV}$ at ILC, and find that the NLO EW corrections, the h.o.ISR contributions and the beamstrahlung eff…
The left-right twin Higgs model (LRTHM) predicts the existence of the top partner $T$. In this work, we make a systematic investigation for the single and pair production of this top partner $T$ through the processes: $e^{+}e^{-}\to t\ov{T} + T\bar{t}$ and $ T\ov{T}$, the neutral scalar (the SM-like Higgs boson $h$ or neutral pseudoscalar boson $ϕ^{0}$) associate productions $e^{+}e^{-}\to t\ov{T}h +T\bar{t}h$, $T\ov{T}h$, $t\ov{T}ϕ^{0}+T\bar{t}ϕ^{0}$ and $ T\ov{T}ϕ^{0}$. From the numerical evaluations for the production cross sections and relevant phenomenological analysis we find that (a) th…
We present a study of triple Higgs boson (3H) production at the International Linear Collider (ILC) within the general Two-Higgs-Doublet Model (2HDM). We compute the production cross-sections at the leading-order for the 3H final states and find values up to sigma ~ 0.1 pb. This result represents a large enhancement with respect to the corresponding MSSM cross-sections, which stay typically at the level of sigma ~ 10^(-6) pb or less. Furthermore, since the 3H cross-sections in the general 2HDM can be of the order of the double Higgs production cross-sections, such 3H processes could be a compe…
We consider possible production of heavy leptons via anomalous interactions at future $ep$ colliders (THERA and LHeC), $e^+e^-$ colliders (ILC and CLIC) and $pp$ collider CERN LHC. The production, backgrounds and signatures of heavy leptons are analyzed. We obtain the upper mass limits of 800 GeV at LHeC, 450 GeV at ILC and 650 GeV at LHC for optimal choices of relevant parameters.
One of the most-studied signals for physics beyond the standard model in the production of gauge bosons in electron-positron collisions is that due to the anomalous triple gauge boson couplings in the $Z γ$ final state. In this work, we study the implications of this at the ILC with polarized beams for signals that go beyond traditional anomalous triple neutral gauge boson couplings. Here we report a dimension-8 CP-conserving $Z γZ$ vertex that has not found mention in the literature. We carry out a systematic study of the anomalous couplings in general terms and arrive at a classification. We…
We review the ILC capabilities to explore the electroweak (EW) sector of the SM at high precision and the prospects of unveiling signals of BSM physics, either through the presence of new particles in higher-order corrections or via direct production of extra EW gauge bosons. This includes electroweak precision observables, global fits to the SM Higgs boson mass as well as triple and quartic gauge boson couplings.
The signature of heavy fermionic triplets belonging to Type III seesaw at the International Linear Collider (ILC) is probed. Presence of charged fermionic triplets upto a mass of about $ 750$ GeV could be established through single production at a 1 TeV ILC with moderate luminosity of 300 fb$^{-1}$, assuming a fermion triplet-electron mixing of about 0.05. Unlike the case of LHC, the production process is highly sensitive to the mixing, making the process interesting. The single production of neutral triplet is found to be somewhat harder, considering the large SM background present. Pair prod…
We study the impact of Higgs precision measurements at a high-energy and high-luminosity linear electron positron collider, such as CLIC or the ILC, on the parameter space of a strongly interacting Higgs boson. Some combination of anomalous couplings are already tightly constrained by current fits to electroweak observables. However, even small deviations in the cross sections of single and double Higgs production, or the mere detection of a triple Higgs final state, can help establish whether it is a composite state and whether or not it emerges as a pseudo-Nambu-Goldstone boson from an under…
The Higgs triplet model (HTM) predicts the existence of a pair of doubly charged Higgs bosons $H^{\pm \pm}$. Single production of $H^{\pm \pm}$ via e collision at the next generation e+e- International Linear Collider (ILC) and the Large Hadron electron Collider (LHeC) is considered. The numerical results show that the production cross sections are very sensitive to the neutrino oscillation parameters. Their values for the inverted hierarchy mass spectrum are larger than those for the normal hierarchy mass spectrum at these two kinds of collider experiments. With reasonable values of the relev…
We investigate the potential of the Compact Linear Collider (CLIC) to probe the anomalous $W^+W^-γ$ coupling in $γγ$, $γγ^*$ and $γ^*γ^*$ collisions through the processes $γγ\rightarrow W^+ W^-$, $e^+ γ\rightarrow e^+ γ^{*} γ\rightarrow e^+ W^- W^+$ and $e^+ e^-\rightarrow e^+ γ^{*} γ^{*} e^- \rightarrow e^+ W^- W^+ e^-$. We perform leptonic, semi-leptonic and hadronic decays channels for $W^+W^-$ production in the final state. Taking ${\cal L}=1\hspace{0.8mm}{\rm ab^{-1}}@ \sqrt{s}=0.380\hspace{0.8mm}{\rm TeV}$, ${\cal L}=2.5\hspace{0.8mm}{\rm ab^{-1}}@ \sqrt{s}=1.5\hspace{0.8mm}{\rm TeV}$ an…
We study the sensitivity of testing the anomalous gauge couplings $g_{HVV}$'s of the Higgs boson in the formulation of linearly realized gauge symmetry via the processes $γγ\to ZZ$ and $γγ\to WWWW$ at polarized and unpolarized photon colliders based on $e^+e^-$ linear colliders of c.m.~energies 500 GeV, 1 TeV, and 3 TeV. Signals beyond the standard model (SM) and SM backgrounds are carefully studied. We propose certain kinematic cuts to suppress the standard model backgrounds. For an integrated luminosity of 1 ab$^{-1}$, we show that (a) $γγ\to ZZ$ can provide a test of $g_{Hγγ}$ to the $3σ$ s…
For both the FCC-ee and the ILC, to exploit properly the respective precision physics program, the theoretical precision tag on the respective luminosity will need to be improved from the analogs of the $ 0.054 \% (0.061\%)$ results at LEP at $M_Z$, where the former (latter) LEP result has (does not have) the pairs correction. At the FCC-ee at $M_Z$ one needs improvement to $0.01\%$, for example. We present an overview of the roads one may take to reach the required $0.01\%$ precision tag at the FCC-ee and of what the corresponding precision expectations would be for the FCC-ee$_{350}$, ILC$_{…
The physics prospect at future linear $e^{+}e^{-}$ colliders for the study of the Higgs triple self-coupling via the process of $e^{+}e^{-}\to ZHH$ is investigated. In this paper, we calculate the contribution of the new particles predicted by the littlest Higgs model to the cross sections of this process in the future high energy $e^{+}e^{-}$ collider($ILC$). The results show that, in the favorable parameter spaces preferred by the electroweak precision, the deviation of the total cross sections from its $SM$ value varies from a few percent to tens percent, which may be detected at the future…
With the prospect of improved Higgs measurements at the LHC and at proposed future colliders such as ILC, CLIC and TLEP we study the non-custodial Randall-Sundrum model with bulk SM fields and compare brane and bulk Higgs scenarios. We compute the electroweak precision observables and argue that incalculable contributions to these, in the form of higher dimensional operators, could have a non-negligable impact. This could potentially reduce the bound on the lowest Kaluza-Klein gauge boson masses to the 5 TeV range, making these states detectable at the LHC. In a second part, we compute the mis…
We explore discrimination of two types of leptonic Yukawa interactions associated with Higgs triplet, $\bar L^c_L ΔL_L$, and with $SU(2)$ singlet doubly charged scalar, $\bar e_R^c k^{++} e_R$. These interactions can be distinguished by measuring the effects of doubly charged scalar boson exchange in the $e^+ e^- \to \ell^+ ell^-$ processes at polarized electron-positron colliders. We study a forward-backward asymmetry of scattering angular distribution to estimate the sensitivity for these effects at the ILC. In addition, we investigate prospects of upper bounds on the Yukawa couplings by com…
Following a brief outline of the CLIC project, this talk summarizes some of the principal motivations for an e+ e- collider with E_CM = 3 TeV. It is shown by several examples that CLIC would represent a significant step beyond the LHC and ILC in its capabilities for precision measurements at high energies. It would make possible a complete study of a light Higgs boson, including rare decay modes, and would provide a unique tool to study a heavy Higgs boson. CLIC could also complete the studies of supersymmetric spectra, if sparticles are relatively light, and discover any heavier sparticles. I…
We investigate the effects induced by the interactions of the Kaluza-Klein (KK) graviton with the standard model (SM) particles on the triple $Z^0$-boson production process at the ILC in the framework of the large extra dimension (LED) model. We present the dependence of the integrated cross sections on the electron-positron colliding energy $\sqrt{s}$, and various kinematic distributions of final $Z^0$ bosons and their subsequential decay products in both the SM and the LED model. We also provide the relationship between the integrated cross section and the fundamental scale $M_S$ by taking t…
We discuss single heavy neutrino production e+ e- -> N nu -> l W nu, l = e, mu, tau, at a future high energy collider like CLIC, with a centre of mass energy of 3 TeV. This process could allow to detect heavy neutrinos with masses of 1-2 TeV if their coupling to the electron V_eN is in the range 0.004-0.01. We study the dependence of the limits on the heavy neutrino mass and emphasise the crucial role of lepton flavour in the discovery of a positive signal at CLIC energy. We present strategies to determine heavy neutrino properties once they are discovered, namely their Dirac or Majorana chara…
We study the contributions of colorless vectorlike fermions to the triple gauge couplings $W^+ W^- γ$ and $W^+ W^- Z^0$. We consider models in which their coupling to the Standard Model Higgs boson is allowed or forbidden by quantum numbers. We assess the sensitivity of the future accelerators FCC-ee, ILC and CLIC to the parameters of these models, assuming they will be able to constrain the anomalous triple gauge couplings with a precision $δκ_V \sim \mathcal{O}(10^{-4})$, $V=γ,Z^0$. We show that the combination of measurements at different center-of-mass energies helps to improve the sensiti…
The hitherto unconstrained lepton flavor mixing, induced by the new charged scalar ϕ^\pm and ϕ^{\pm\pm} predicted by many new physics models such as higgs triplet models, may lead to the lepton flavor violating productions of τ\bar μ, τ\bar e and μ\bar e in photon-photon collision at the proposed international linear collider. In this paper, we consider the contributions of the ϕ^\pm and ϕ^{\pm\pm} in the context of the higgs triplet models to the processes γγ\to l_i\bar l_j (i, j= e, μ, τ, i\neq j) and find that they can be good channels to probe these new physics models. The lepton flavor vi…
The measure of the triple Higgs coupling is one of the major goals of the high-luminosity run of the CERN Large Hadron Collider (HL-LHC) as well as the future colliders, either leptonic such as the International Linear Collider (ILC) or hadronic such as the 100 TeV Future Circular Collider in hadron-hadron mode (FCC-hh). We have recently proposed this observable as a test of neutrino mass generating mechanisms in a regime where heavy sterile neutrino masses are hard to be probed otherwise. We present in this article a study of the one-loop corrected triple Higgs coupling in the inverse seesaw …
In this report I discuss physical problems for future Photon Colliders (PLC), which can be stated AFTER 10 years of work of LHC and few years of work of e^+e^- ILC. I discuss mainly the unfavorable case when these colliders will give us only Higgs boson(s) and perhaps some charged particles of unclear nature. I focus my attention for the case of PLC based on the second stage of ILC (about 1 TeV) or CLIC (1-3 TeV). It offers opportunity to study new series of fundamental physical problems. Among them - multiple production of gauge bosons, hunt for strong interaction in Higgs sector, search of e…
The Higgs Triplet Model (HTM) is one of important examples for extended Higgs sectors, because tiny neutrino masses can be simply explained. Unlike the canonical type-I seesaw model, a scale of new particles can be taken as $\mathcal{O}(100)$ GeV keeping an enough amount of production cross section for direct searches at collider experiments. In the HTM, there appear doubly-charged Higgs bosons $H^{\pm\pm}$, and detection of them is a key to probe the model. The decay property of $H^{\pm\pm}$ depends on the magnitude of the vacuum expectation value of the triplet field $v_Δ$. When $v_Δ$ is sma…
We consider the neutral triple gauge boson production process in the context of large extra dimensions (LED) model including the Kaluza-Klein (KK) excited gravitons at future linear colliders, say ILC(CLIC). We consider $γγγ, γγZ, γZ Z$ and $ZZZ$ production processes, and analyse their impacts on both the total cross section and some key distributions. These processes are important for new physics searches at linear colliders. Our results show that KK graviton exchange has the most significant effect on \eerzz among the four processes with relatively small $M_S$, while it has the largest effec…
We present a study of the sensitivity of an International Linear Collider (ILC) to electroweak parameters in the absence of a light Higgs boson. In particular, we consider those parameters that have been inaccessible at previous colliders, quartic gauge couplings. Within a generic effective-field theory context we analyze all processes that contain quasi-elastic weak-boson scattering, using complete six-fermion matrix elements in unweighted event samples, fast simulation of the ILC detector, and a multidimensional parameter fit of the set of anomalous couplings. The analysis does not rely on s…
We consider scenarios in which the lightest sparticle (LSP) is the gravitino and the next-to-lightest sparticle (NLSP) is a metastable stau. We examine the production of stau pairs in e^{+}e^{-} annihilation at ILC and CLIC energies. In addition to three minimal supergravity (mSUGRA) benchmark scenarios proposed previously, we consider a new high-mass scenario in which effects catalyzed by stau bound states yield abundances of {6,7}Li that fit the astrophysical data better than standard Big-Bang nucleosynthesis. This scenario could be probed only at CLIC energies. In each scenario, we show how…
We estimate the possible accuracies of measurements at the proposed CLIC $e^+e^-$ collider of Higgs and $W^+W^-$ production at centre-of-mass energies up to 3TeV, incorporating also Higgsstrahlung projections at higher energies that had not been considered previously, and use them to explore the prospective CLIC sensitivities to decoupled new physics. We present the resulting constraints on the Wilson coefficients of dimension-6 operators in a model-independent approach based on the Standard Model effective field theory (SM EFT). The higher centre-of-mass energy of CLIC, compared to other proj…
We investigate the scenario where the dark matter only interacts with the charged leptons in the standard model via a neutral vector mediator $Z'$. Such a scenario with a 430 GeV dark matter can fit the recent positron fluxes observed by the AMS-02 Collaborations, with the reasonable boost factors. We study the possibility of searching such leptophilic $Z'$ via its lepton final states and invisible decay modes at the future electron-positron colliders, such as the International Linear Collider (ILC) and the Compact Linear Collider (CLIC). We find that for the benchmark models with $Z'$ mass fr…
A new particle with mass ~ 125 GeV that resembles the Higgs boson has recently been discovered by ATLAS and CMS. We propose a low-energy gamma-gamma collider as a cost- and time-efficient option for a Higgs factory capable of studying this particle in detail. In the past, this option has been suggested as a possible application of the CLIC two-beam accelerator technology (the CLIC Higgs Experiment, CLICHE) or as an option for the ILC. Here we propose a design based on a pair of \sim 10 GeV recirculating Linacs (Small Accelerator for Photon-Photon Higgs production using Recirculating Electrons,…
We discuss the parity-violating left-right asymmetries (LRAs) in Möller scattering at the International Linear Collider (ILC) induced by doubly charged Higgs bosons in models with $SU(2)_L$ triplet and singlet scalar bosons, which couple to the left- and right-handed charged leptons, respectively. These bosons are important in the scenarios for the generation of the neutrino mass. We demonstrate that the contributions to the LRAs from the triplet and singlet bosons are opposite to each other. In particular, we show that the doubly charged Higgs boson from the singlet scalar can be tested at th…
In this paper I review the calculations (and partially simulations and theoretical studies) that have been made and published during the last two to three years focusing on the electroweak symmetry breaking sector and the Higgs boson(s) within the Standard Model and models beyond the Standard Model (BSM) at or relevant for either the International Linear Collider (ILC) or the Compact Linear Collider (CLIC), commonly abbreviated as Linear Collider (LC).
The feature of extended Higgs models can appear in the pattern of deviations from the Standard Model (SM) predictions in coupling constants of the SM-like Higgs boson ($h$). We can thus discriminate extended Higgs models by precisely measuring the pattern of deviations in the coupling constants of $h$, even when extra bosons are not found directly. In order to compare the theoretical predictions to the future precision data at the ILC, we must evaluate the theoretical predictions with radiative corrections in various extended Higgs models. In this talk, we give our comprehensive study for radi…
With the prospect of improved Higgs measurements at the LHC and at proposed future colliders such as ILC, CLIC and TLEP we study the non-custodial Randall-Sundrum model with bulk SM fields and compare brane and bulk Higgs scenarios. The latter bear resemblance to the well studied type III two-Higgs-doublet models. We compute the electroweak precision observables and argue that incalculable contributions to these, in the form of higher dimensional operators, could have an impact on the T-parameter. This could potentially reduce the bound on the lowest Kaluza-Klein gauge boson masses to the 5 Te…
An important task at future colliders is the investigation of the Higgs-boson sector. Here the measurement of the triple Higgs coupling(s) plays a special role. Based on previous analyses, within the framework of Two Higgs Doublet Models (2HDM) type~I and~II, we define and analyze several two-dimensional benchmark planes, that are over large parts in agreement with all theoretical and experimental constraints. For these planes we evaluate di-Higgs production cross sections at future high-energy $e^+e^-$ colliders, such as ILC or CLIC. We consider two different channels for the neutral di-Higgs…
We studied the production and signatures of doubly charged Higgs bosons in the process $γe^- \rightarrow H^{--}E^+$, where $E^+$ is a heavy lepton, at the $e^-e^+$ International Linear Collider (ILC) and CERN Linear Collider (CLIC). The intermediate photons are given by the Weizs$\ddot{a}$cker-Williams and laser backscattering distributions. We found that significant signatures are obtained by bremsstrahlung and backward Comptom scattering of laser. A clear signal can be obtained for doubly charged Higgs bosons, doubly charged gauge bosons and heavy leptons.
We investigate $e^{+}e^{-}\to γγ$ process within the Seiberg-Witten expanded noncommutative standard model(NCSM) scenario in the presence of anomalous triple gauge boson couplings. This study is done with and without initial beam polarization and we restrict ourselves to leading order effects of non commutativity i.e. $O(Θ)$. The non commutative(NC) corrections are sensitive to the electric component($\vecΘ_E$) of NC parameter. We include the effects of earth rotation in our analysis. This study is done by investigating the effects of non commutativity on different time averaged cross section …
We study the process e+e- -->nu nubar gamma to search for its sensitivity to the extra gauge bosons Z_2, Z_3 and W_2 which are suggested by the little Higgs models. We find that the ILC with sqrt(s)=0.5 TeV and CLIC with sqrt(s)=3 TeV cover different regions of the LHM parameters. We show that this channel can provide accurate determination of the parameters, complementary to measurements of the extra gauge bosons at the coming LHC experiments.
The pairwise production of neutral Higgs bosons is analyzed in the context of the future linear colliders, such as the ILC and CLIC, within the general Two-Higgs-Doublet Model (2HDM). The corresponding cross-sections are computed at the one-loop level in full compliance with the current phenomenological bounds and the stringent theoretical constraints inherent to the consistency of the model. We uncover regions across the 2HDM parameter space, mainly for low tanβnear 1 and moderate values of the relevant lambda_5 parameter, wherein the radiative corrections to the Higgs-pair production cross s…
