7 pages, 2 figues. Talk presented at the International Workshop on Future Linear Colliders (LCWS2019), Sendai, Japan, 28 October-1 November, 2019. C19-10-28. Based on arXiv:1903.11661 and arXiv:1910.06858
The CMS collaboration reported an intriguing \sim 3 sigma (local) excess at 96 GeV in the light Higgs-boson search in the diphoton decay mode. This mass coincides with a \sim 2 sigma (local) excess in the bb final state at LEP. We present the interpretation of this possible signal as the lightest Higgs boson in the 2 Higgs Doublet Model with an additional real Higgs singlet (N2HDM). It is shown that the type II and type IV (flipped) of the N2HDM can perfectly accommodate both excesses simultaneously, while being in agreement with all experimental and theoretical constraints. The excesses are most easily accommodated in the type II N2HDM, which resembles the Yukawa structure of supersymmetric models. We discuss the experimental prospects for constraining our explanation at future $e^+e^-$ colliders, with concrete analyses based on the ILC prospects.
The recently reported diphoton excess at the LHC may imply the existence of a new resonance with a mass of about 750 GeV which couples to photons via loops of new charged particles. In this letter, we study the possibility to test such models at the ILC, paying attention to the new charged particles responsible for the diphoton decay of the resonance. We show that they affect the scattering processes $e^+e^- \to f\bar{f}$ (with $f$ denoting Standard Model fermions) at the ILC, which makes it possible to indirectly probe the new charged particles even if they are out of the kinematical reach. W…
We assume that the 125 GeV Higgs discovered at the LHC is the heavy CP-even Higgs of the two-Higgs-doublet models, and examine the parameter space in the Type-I, Type-II, Lepton-specific and Flipped models allowed by the latest Higgs signal data, the relevant experimental and theoretical constraints. Further, we show the projected limits on $\tanβ$, $\sin(β-α)$, $Hf\bar{f}$ and $HVV$ couplings from the future measurements of the 125 GeV Higgs at the LHC and ILC, including the LHC with integrated luminosity of 300 fb$^{-1}$ (LHC-300 fb$^{-1}$) and 3000 fb$^{-1}$ (LHC-3000 fb$^{-1}$) as well as …
The LEP experiments give a lower bound on the neutralino mass of about 46 GeV which, however, relies on a supersymmetric grand unification relation. Dropping this assumption, the experimental lower bound on the neutralino mass vanishes completely. Recent analyses suggest, however, that in the minimal supersymmetric standard model (MSSM), a light neutralino dark matter candidate has a lower bound on its mass of about 7 GeV. In light of this, we investigate the mass sensitivity at the ILC for very light neutralinos. We study slepton pair production, followed by the decay of the sleptons to a lep…
The plan for the International Linear Collider (ILC) is now being prepared as a staged design, with the first stage of 2 ${\rm ab^{-1}}$ at 250GeV and later stages achieving the full project specifications with 4 ${\rm ab^{-1}}$ at 500 GeV. The talk presents the capabilities for precision Higgs boson measurements at 250 GeV. It is shown that the 250 GeV stage of the ILC will already provide many compelling results in Higgs physics, with new measurements unavailable at the Large Hadron Collider, model-independent determinations of key parameters, and possible discrimination of a variety of scen…
The plan for the International Linear Collider is now being prepared as a staged design, with the first stage at 250 GeV and later stages achieving the full project specifications with 4 ab-1 at 500 GeV. This talk will present the capabilities for precision Higgs boson measurements at 250 GeV and their relation to the full ILC program. It will show that the 250 GeV stage of ILC will already provide many compelling results in Higgs physics, with new measurements not available at LHC, model-independent determinations of key parameters, and tests for and possible discrimination of a variety of sc…
The historic LHC discovery of the 125 GeV particle with properties that closely resemble the Standard Model (SM) Higgs boson verifies our understanding of electroweak symmetry breaking, but solidifies the need for a resolution to the hierarchy problem. Many extensions of the SM that address the hierarchy problem contain a non-minimal Higgs sector. Therefore, as a benchmark alternative to the SM Higgs mechanism, we study a general 2 Higgs doublet model (2HDM-G) framework for evaluating future sensitivity to Higgs couplings. We study how well it can be distinguished from the SM Higgs boson by fu…
The ILC Technical Design Report documents the design of a 500 GeV linear collider, but does not specify the center-of-mass energy steps of operation for the collider. The ILC Parameters Joint Working Group has studied possible running scenarios, including a realistic estimate of the real time accumulation of integrated luminosity based on ramp-up and upgrade processes, and considered the evolution of the physics outcomes. These physics goals include Higgs precision measurements, top quark measurements and searches for new physics. We present an "optimized" operating scenario and the anticipate…
In the gauge-Higgs unification scenario the 4D Higgs field is identified with the zero mode of the extra-dimensional component of gauge potentials. The mass of the Higgs particle in the unification in the Randall-Sundrum warped spacetime is predicted to be in the range 100 GeV - 300 GeV. The WWZ gauge couplings remains almost universal as in the standard model, but substantial deviation results for the Higgs couplings. The WWH and ZZH couplings are suppressed by a factor \cos θ_H from the values in the standard model, where θ_H is the Yang-Mills AB phase along the fifth dimension. These can be…
We outline a systematic approach to the determination of the Standard Model-like Higgs boson total width and measurable coupling parameters in a model-independent manner at the International Linear Collider (ILC) and illustrate the complementarity for operating the ILC at $250$ GeV near the $Zh$ threshold and at $500$ GeV and $1$ TeV utilizing the $WW, ZZ$ fusion processes. We perform detailed simulations for an important contributing channel to the coupling determination and for invisible decays. Without model assumptions, and combining the information for the coupling ratios from the LHC, th…
Precise measurements of electroweak processes at the International Linear Collider (ILC) will provide unique opportunities to explore new physics beyond the Standard Model. Fermion pair productions are sensitive to a new contact interaction or a new heavy gauge boson by comparing cross section and angular distribution with expectations of the new physics models. In this proceedings we report a simulation study of fermion pair productions at a center-of-mass energy of 250 GeV, with a focus on lepton pairs, to demonstrate the potential of the first phase of the ILC.
We study the possibility of using W pair production and leptonic decay of one of the W's at the ILC with polarized beams as a probe of the Littlest Higgs Model. We consider cross-sections, polarization fractions of the W's, leptonic decay energy and angular distributions, and left-right polarization asymmetry as probes of the model. With parameter values allowed by present experimental constraints detectable effects on these observables at typical ILC energies of 500 GeV and 800 GeV will be present. Beam polarization is further found to enhance the sensitivity.
Precise measurements of electroweak processes at the International Linear Collider (ILC) will provide unique opportunities to explore new physics beyond the Standard Model. Fermion pair production events are sensitive to new interactions involving a new heavy gauge boson or an electroweak interacting massive particle (EWIMP).We studied the mass reach of new particles at the ILC with $\sqrt{s}=250$ GeV by using $e^+ e^-\to e^+ e^-$and $e^+ e^-\to μ^+ μ^-$ events. We show that a mass reach for BSM particles can be determined with 90% confidence level using a toy Monte Carlo technique.
Direct constraints on the masses of new heavy bosons by the Tevatron data are discussed. Some excesses in the experimental data are interpreted as a resonance production of new charged and `leptophobic' neutral chiral bosons with masses around 500 GeV and 700 GeV, respectively. The interpretation was provided on the basis of the theoretical model, proposed by the author about 15 years ago. New Tevatron data and the LHC results will definitely confirm or reject this interpretation. The ILC with an energy above 1 TeV would be an ideal place to produce and to study the properties of these particl…
For some theoretical and experimental considerations, the relatively light Majorana neutrinos at the GeV scale have been attracting some interest. In this article we consider a scenario with only one Majorana neutrino $N$, negligible mixing with the active neutrinos $ν_{L}$, where the Majorana neutrino interactions could be described in a model independent approach based on an effective theory. Under such a framework, we particularly study the feasibility of observing the $N$ with mass in the range 0$-$30 GeV via the process $e^+ e^- \to νN \toγ+ \slashed E$ in the future Belle-II and ILC expe…
We report on the feasibility of the direct measurement of the top Yukawa coupling g_t at the International Linear Collider (ILC) during its first phase of operation with a center-of-mass energy of 500 GeV. The signal and background models incorporate the non-relativistic QCD corrections which enhance the production cross section near the t-tbar threshold. The e+e- -> t tbar H signal is reconstructed in the 6-jet + lepton and the 8-jet modes. The results from the two channels are combined. The background processes considered are e+e- -> t bbar W- / tbar b W+ (which includes e+e- -> t tbar), e+e…
This document is the final report by the Committee on the Scientific Case of the ILC Operating at 250 GeV as a Higgs Factory. This committee was commissioned by the Japan Association of High Energy Physicists. The purpose of this committee is to investigate and compare the capability to determine the energy scale of new phenomena and new principles and the capability to uncover the origin of matter-antimatter asymmetry.
The measurement of hadronic Higgs Boson branching ratios H -> bb, H -> gg for a light Standard Model-like Higgs boson produced at 250 GeV centre of mass energy at the International Linear Collider (ILC) is presented. The tools and techniques used for the analysis are briefly discussed.
We study the complete ${\cal O}(α_{ew})$ electroweak (EW) corrections to the production of three $Z^0$-bosons in the the framework of the standard model(SM) at the ILC. The leading order and the EW next-to-leading order corrected cross sections are presented, and their dependence on the colliding energy $\sqrt{s}$ and Higgs-boson mass $m_{H}$ is analyzed. We investigate also the LO and one-loop EW corrected distributions of the transverse momentum of final $Z^0$ boson, and the invariant mass of $Z^0Z^0$-pair. Our numerical results show that the EW one-loop correction generally suppresses the t…
We study the effect of theoretical and parametric uncertainties on the ability of future Higgs coupling measurements at the International Linear Collider (ILC) to reveal deviations from the Standard Model (SM). To quantify the impact of these uncertainties we plot Delta chi^2 = 25 contours for the deviations between the SM Higgs couplings and the light Higgs couplings in the mh-max benchmark scenario of the Minimal Supersymmetric Standard Model (MSSM). We consider the theoretical uncertainties in the SM Higgs decay partial widths and production cross section and the parametric uncertainties in…
The International Linear Collider is now proposed with a staged machine design, with the first stage at $\sqrt{s}=250$ GeV and an integrated luminosity goal of 2 ab${}^{-1}$. One of the questions for the machine design is the importance of positron polarization. In this report, we review the impact of positron polarization on the physics goals of the 250 GeV stage of the ILC and demonstrate that positron polarization has distinct advantages.
Precise predictions for an $e^+e^-\rightarrow t\bar{t}$ cross-section are presented in the energy region from 400 GeV to 800 GeV. Cross-sections are estimated including the beam-polarization effects with full $\mathcal{O}(α)$, and also with the effects of the initial-state photon emission. A radiator technique is used for the initial-state photon emission up to two-loop orders. In this investigation, a weak correction is defined as the full electroweak corrections without the initial-state photonic corrections. As a result, it is determined that the total cross-section of a top quark pair-prod…
In this work we investigate the Higgs pair production in the MSSM and NMSSM at the photon-photon collision of the ILC. We consider various experimental constraints and scan over the parameter space of the MSSM and NMSSM. Then we calculate the cross section of Higgs pair production in the allowed parameter space and compare the results with the predictions in the SM. We find that the large enhancement of the cross section in the MSSM is mainly due to the contributions from the loops mediated by the stau, while in the NMSSM it is mainly due to the contributions from the top-squark loops. For lig…
We present an analysis for the measurement of the Higgs boson branching ratio H-> cc-bar for a light Standard Model-like Higgs boson produced at 250 GeV centre of mass energy at the International Linear Collider (ILC). The tools and technique used for the analysis are described and relative uncertainties are determined.
Precise predictions for an $e^+e^-\rightarrow t\bar{t}$ cross section are presented at an energy region from 400 GeV to 800 GeV. Cross sections are estimated including the beam-polarization effects with full $\mathcal{O}(α)$, and also with effects of the initial-state photon emission. A radiator technique is used for the initial-state photon emission up to two-loop order. A weak correction is defined as the full electroweak corrections without the initial-state photonic corrections. As a result, it is obtained that the total cross section of a top quark pair-production receives the weak correc…
This document is meant to provide semi-quantitative arguments to evaluate the luminosity needed at ILC to achieve a precise measurement of the Higgs mass, width and invisible decays. It is shown that for mH=120 GeV, one can save an order of magnitude on the luminosity needed to achieve a given precision on the Higgs mass, as compared to what can be obtained at \sqrt s=350 GeV, by running near threshold. Since the recoil mass resolution near threshold is independent of the Higgs mass, one can also access the Higgs width for masses above 170 GeV. This strategy of running just above threshold is …
The discovery of the 125 GeV Higgs boson and the measurement of its branching ratios has initiated the exploration of the electroweak symmetry breaking sector. There have been numerous studies exploring the restrictions these results place on the parameter space of two Higgs doublet models. We extend these results to include the full data set and study the expected sensitivity that can be obtained with 300 and 3000 inverse femtobarn of integrated luminosity. In addition, searches for a heavy Standard Model Higgs boson are also considered. It is shown that the nonobservation of such a Higgs bos…
We study the search for an extra scalar $S$ boson produced in association with the $Z$ boson at the International Linear Collider (ILC). The study is performed at center-of-mass energies of 250 GeV and 500 GeV based on the full simulation of the International Large Detector (ILD). In order to be as model-independent as possible, the analysis uses the recoil technique, in particular with the $Z$ boson decaying into a pair of muons. As a result, exclusion cross-section limits are given in terms of a scale factor $k$ with respect to the Standard Model Higgs-strahlung process cross section. These …
Experimental searches for Axion-Like Particles (ALPs) which couple to the electroweak bosons span over a wide range of ALP masses, from MeV searches at beam-dump experiments, to TeV searches at the LHC. Here we examine an interesting range of parameter space in which the ALP couples only to hypercharge. In the GeV to hundreds of GeV mass range, the contribution of an ALP to light by light scattering can be significant. By making simple kinematic cuts, we show that the ILC running at $\sqrt{s} = 250\,\rm{GeV}$ or $\sqrt{s} = 500\,\rm{GeV}$ can discover ALPs in this range of masses with signific…
Spin identification of the mono-Z$^{\prime}$ resonance in muon-pair production at the ILC with simulated electron-positron collisions at $\sqrt{s}$ = 500 GeV
Centre for Theoretical Physics, The British University in Egypt（埃及英国大学理论物理中心）
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.
The precision measurements of the Higgs properties is crucial for a better understanding of electroweak symmetry breaking. It can be first achieved at the ILC\pcite{Behnke2013} at $\sqrt{s}=250\rm ~GeV$ via the Higgs-strahlung production process $e^+e^-\rightarrow ZH$. The hadronic decay mode $Z\rightarrow \bar{q}q$ constitutes more than $65%$ of the total, a factor 10 more than $Z\rightarrow μμ$. An analysis based solely on the $Z$ jet pair information could thus lead to a high statistics and provide a minimum biased Higgs sample. A study of the feasibility of such analysis is shown here, bas…
Investigating vector-like leptons decaying into an electron and missing transverse energy in e$^{+}$ e$^{-}$ collisions with $\sqrt{s} = 500$ GeV at the ILC
In this work, we analyze three dominant single SM-like Higgs boson production processes in the left-right twin Higgs model (LRTHM): the Higgs-strahlung (HS) process $e^{+}e^{-}\rightarrow Zh$, the vector boson fusion (VBF) process $e^{+}e^{-}\to ν\barνh$ and the associate production with top pair process $e^{+}e^{-}\to t\bar{t}h$ for three possible energy stages of the International Linear Collider (ILC), and compared our results with the expected experimental accuracies for various accessible Higgs decay channels. The following observations have been obtained: (i) In the reasonable parameter …
We make a systematic and comparative study for the LHC and ILC for the electroweakino searches in the Minimal Supersymmetric Standard Model. We adopt a general bottom-up approach and scan over the parameter regions for all the three cases of the lightest supersymmetric particle being Bino-, Wino-, and Higgsino-like. The electroweakino signal from pair production and subsequent decay to Wh (h to b\bar b) final state may yield a sensitivity of 95% C.L. exclusion (5sigma discovery) to the mass scale M_2, mu ~ 250-400 GeV (200-250 GeV) at the 14 TeV LHC with an luminosity of 300 fb^{-1}. Combining…
We present a study of the Higgs boson decay branching ratios to $b\bar{b}$, $c\bar{c}$ and gluons, one of the cornerstones of the physics program at the International Linear Collider (ILC). A standard model Higgs boson of 120\,GeV mass, produced in the Higgs-strahlung process at $\sqrt{s} = 250$\,GeV was investigated using the full detector simulation and reconstruction procedures. The analysis was performed in the framework of the Silicon Detector (SiD) concept with full account of inclusive standard model backgrounds. The selected decay modes contained two heavy flavour jets in the final sta…
We evaluate the $e^- e^+ \to e^- e^+ +h$ process through the $ZZ$ fusion channel at the International Linear Collider (ILC) operating at $500$ GeV and $1$ TeV center of mass energies. We perform realistic simulations on the signal process and background processes. With judicious kinematic cuts, we find that the inclusive cross section can be measured to $2.9\%$ after combining the $500$ GeV at $500 \text{fb}^{-1}$ and $1$ TeV at $1~ \text{ab}^{-1}$ runs. A multivariate log-likelihood analysis further improves the precision of the cross section measurement to $2.3\%$. We discuss the overall imp…
In this study, the charged Higgs pair production is analyzed for the minimal extension of the standard model called two-higgs-doublet model. The process $γγ\rightarrow H^+H^-$ is calculated at the tree level for the ILC and the numerical analysis is presented for various parameters. The production rate of the charged Higgs boson pair as a function of center-of-mass (CM) energy and the differential cross section as a function of angle between photon and positive charged Higgs boson is presented. The cross section gets high at the low charged Higgs mass and low CM energies. The total integrated …
We consider a gauged U(1)$_{B-L}$ (Baryon-minus-Lepton number) extension of the Standard Model (SM), which is anomaly-free in the presence of three Right-Handed Neutrinos (RHNs). Associated with the U(1)$_{B-L}$ symmetry breaking the RHNs acquire their Majorana masses and then play the crucial role to generate the neutrino mass matrix by the seesaw mechanism. Towards the experimental confirmation of the seesaw mechanism, we investigate a RHN pair production through the U(1)$_{B-L}$ gauge boson ($Z^\prime$) at the 250 GeV International Linear Collider (ILC). The $Z^\prime$ gauge boson has been …
Axion-Like Particles (ALPs) are a generic, calculable, and well motivated extension of the Standard Model with far reaching phenomenology. ALPs that couple only to hypercharge represent one subset of such models, coupling the ALP to both photons and the $Z$ boson. We examine the current constraints on this class of models with an ALP mass in the 100 MeV to 100 GeV range, paying particular attention to the region between 100 MeV to 10 GeV, a portion of parameter space which is ill constrained by current experiments. We show that the more than $10^{9}$ $Z$ bosons produced in the Giga-Z mode of t…
We evaluate the measurement accuracy of the branching ratio of $h \to τ^+ τ^-$ at $\sqrt{s} = 250$ GeV and 500 GeV at the ILC with the ILD detector simulation. For the $\sqrt{s} = 250$ GeV, we assume the Higgs mass of $M_h = 120$ GeV, branching ratio of $\mathrm{Br}(h \to τ^+ τ^-) = 8.0 \ %$, beam polarization of $P(e^-, e^+) = (-0.8, +0.3)$, and integrated luminosity of $\int L \ dt = 250 \ \mathrm{fb ^{-1}}$. The Higgs-strahlung process $e^+ e^- \to Zh$ with $Z \to e^+ e^-$, $Z \to μ^+ μ^-$, $Z \to q\bar{q}$ mode are analyzed. The measurement accuracy is calculated to be $Δ(σ\cdot \mathrm{Br…
International Linear Collider (ILC) is an electron-positron collider with the initial center-of-mass energy of 500 GeV which is upgradable to about 1 TeV later on. Its goal is to study the physics at TeV scale with unprecedented high sensitivities. The main topics include precision measurements of the Higgs particle properties, studies of supersymmtric particles and the underlying theoretical structure if supersymmetry turns out to be realized in nature, probing alternative possibilities for the origin of mass, and the cosmological connections thereof. In many channels, Higgs and leptonic sect…
This article is based on the talk presented at the International Workshop on Future Linear Colliders (LCWS13) which held during November 11-15, 2013 at Tokyo, Japan. We present several analyses related to the Higgs total width study at ILC based on the full detector simulation of ILD, which are \eevvH followed by \Htobb and \HtoWW. The studies show that at $\unit{250}{GeV}$ we can determine the Higgs total width with a relative precision of 11% and the $HWW$ coupling with 4.8%, whereas at $\unit{500}{GeV}$ the expected precision can be significantly improved to 5% and 1.2% respectively, assumi…
A weak singlet charged scalar exists in many new physics models beyond the Standard Model. The discovery potential of the singlet charged scalar is explored at future lepton colliders, e.g. the CEPC, ILC-350 and ILC-500. We demonstrate that one can discover the singlet charged scalar up to 118 GeV at the CEPC with an integrated luminosity of $5~\mathrm{ab}^{-1}$. At the ILC-350 and the ILC-500 with an integrated luminosity of $1~\mathrm{ab}^{-1}$ such a discovery limit can be further improved to 136 GeV and 160 GeV, respectively.
This document discusses for the first time the experimental prospects on the measurement of cross section and the forward-backward asymmetry in $e^{-}e^{+}\rightarrow c\bar{c}$ collisions at 250 GeV at the International Linear Collider operating polarised beams. The cross section will be normalised to the total hadronic cross section. We discuss the results for an analysis assuming the integrated luminosity of 2000 fb$^{-1}$ foreseen in the baseline project. The measurement requires determining the charge of both jets identified as originated by a $c$-quark. The charge measurement is optimally…
We investigate the possibility of detecting hidden vector gauge bosons at ILC linear collider. The study is performed in the framework of hidden sector extension of Standard Model with 3 degenerate dark gauge bosons. By studying the cross section of pair dark gauge boson with photon at initial state radiation we found that at the energy $\sqrt{s} \approx$ 1300 GeV the cross section can be as large as $48fb$, the same order ($\mathcal{O}(fb)$) with the irreducible background of the Standard Model. Hence more methods needed to be done to eliminate the background for this model.
The precise investigation of the $W^+ W^-Z^0$ production at the $e^+e^-$ International Linear Collider(ILC) is of crucial importance in probing the couplings between massive vector gauge bosons and discovering the signature of new physics beyond the standard model(SM). We study the full one-loop EW effects on the observables, such as, the total cross section, the differential cross section of the invariant mass of $W$-pair, the distribution of the angle between $W$-pair, the production angle distributions of $W$- and $Z^0$-boson, the distributions of the transverse momenta of final $W$- and $Z…
This note presents an analysis of the potential of future high-energy electron-positron colliders to measure the $b$-quark mass. We perform a full-simulation study of the measurement of the ratio of the three-jet rates in events with $b\bar{b}(g)$ and $q\bar{q}(g)$ production, $R_{3}^{bl}$, and assess the dominant uncertainties, including theory and experimental systematic uncertainties. We find that the ILC "Higgs factory" stage, with an integrated luminosity of 2 ab$^{-1}$ at $\sqrt{s}=$ 250 GeV can measure the $b-$quark $bar{MS}$ mass at a scale of 250 GeV ($m_b(250~$GeV$)$) with a precisio…
The Higgs-boson production in association with a W-boson pair at $e^+e^-$ linear colliders is one of the important processes in probing the coupling between Higgs-boson and vector gauge bosons and discovering the signature of new physics. We describe the impact of the complete electroweak(EW) radiative corrections of ${\cal O}(α_{ew})$ to this process in the standard model(SM) at the International Linear Collider(ILC), and investigate the dependence of the lowest-order(LO) and EW next-to-leading order(NLO) corrected cross sections on colliding energy $\sqrt{s}$ and Higg-boson mass. The LO and …
Search for the production of dark matter in the framework of Mono-Z$^{\prime}$ portal at the ILC simulated electron-positron collisions at $\sqrt{s} = 500$ GeV
We evaluate the expected measurement accuracy of the branching ratio of the Standard Model Higgs boson decaying into tau lepton pairs $h \to τ^+ τ^-$ at the ILC with a center-of-mass energy of $\sqrt{s} = 500$ GeV with a full simulation of the ILD detector. We assume a Higgs mass of $M_h = 125$ GeV, a branching ratio of $\mathrm{BR}(h \to τ^+ τ^-) = 6.32 \%$, beam polarizations of $P(e^+, e^-) = (-0.8,+0.3)$, and an integrated luminosity of $\int L dt = 500 \mathrm{fb^{-1}}$. The Higgs-strahlung process $e^+ e^- \to Zh$ with $Z \to q \overline{q}$ and the $WW$-fusion process $e^+ e^- \to ν\ove…
In this work we study a scalar field dark matter model with mass of the order of 100 MeV. We assume dark matter is produced in the process $e^-+e^+\to ϕ+ϕ^*+γ$, that, in fact, could be a background for the standard process $e^-+e^+\to ν+\barν+γ$ extensively studied at LEP. We constrain the chiral couplings, $C_L$ and $C_R$, of the dark matter with electrons through an intermediate fermion of mass $m_F=100$ GeV and obtain $C_L=0.1(0.25)$ and $C_R=0.25(0.1)$ for the best fit point of our $χ^2$ analysis. We also analyze the potential of ILC to detect this scalar dark matter for two configurations…
The ILC Technical Design Report documents the design for the construction of a linear collider which can be operated at energies up to 500 GeV. This report summarizes the outcome of a study of possible running scenarios, including a realistic estimate of the real time accumulation of integrated luminosity based on ramp-up and upgrade processes. The evolution of the physics outcomes is emphasized, including running initially at 500 GeV, then at 350 GeV and 250 GeV. The running scenarios have been chosen to optimize the Higgs precision measurements and top physics while searching for evidence fo…
We discuss a $\sim 3\,σ$ signal (local) in the light Higgs-boson search in the diphoton decay mode at $\sim 96$ GeV as reported by CMS, together with a $\sim 2\,σ$ excess (local) in the $b \bar b$ final state at LEP in the same mass range. We interpret this possible signal as a Higgs boson in the 2 Higgs Doublet Model type II with an additional Higgs singlet, which can be either complex (2HDMS) or real (N2HDM). We find that the lightest CP-even Higgs boson of the two models can equally yield a perfect fit to both excesses simultaneously, while the second lightest state is in full agreement wit…
The ILC Higgs White Paper is a review of Higgs Boson theory and experiment at the International Linear Collider (ILC). Theory topics include the Standard Model Higgs, the two-Higgs doublet model, alternative approaches to electroweak symmetry breaking, and precision goals for Higgs boson experiments. Experimental topics include the measurement of the Higgs cross section times branching ratio for various Higgs decay modes at ILC center of mass energies of 250, 500, and 1000 GeV, and the extraction of Higgs couplings and the total Higgs width from these measurements. Luminosity scenarios based o…
The prediction of additional Higgs bosons is one of the key features of physics beyond the Standard Model (SM) that gives rise to an extended Higgs sector. We assess the sensitivity of the Large Hadron Collider (LHC) in the high luminosity (HL) run alone and in combination with a possible future International Linear Collider (ILC) to probe heavy neutral Higgs bosons. We employ the Minimal Supersymmetric Standard Model (MSSM) as a framework and assume the light CP-even MSSM Higgs boson to be the Higgs boson observed at 125 GeV. We discuss the constraints on the MSSM parameter space arising from…
Non-decoupling D-term extensions of the MSSM enhance the tree-level Higgs mass compared to the MSSM, therefore relax fine-tuning and may allow lighter stops with rather low masses even without maximal mixing. We present the anatomy of various non-decoupling D-term extensions of the MSSM and explore the potential of the LHC and of the International Linear Collider (ILC) to determine their deviations in the Higgs couplings with respect to the Standard Model. Depending on the mass of the heavier Higgs $m_H$, such deviations may be constrained at the LHC and determined at the ILC. We evaluate the …
