Search

I give a short summary on scenarios with new physics scalars that could be investigated at future $e^+e^-$ colliders. I concentrate on cases where at least one of the additional scalar has a mass below 125 GeV, and discuss models where this could be realized. Most of the material presented here has already been discussed in arXiv:2307.15962, and I therefore try to focus on novel developments since then., Comment: 10 pages, 6 figures, Contribution to proceedings of LCWS 2024, International Workshop on Future Linear Colliders

Interference effects are well founded from the quantum mechanical viewpoint and in principle cannot be ignored in realistic studies of New Physics scenarios. In this work, we investigate the size of interference effects between resonant and non-resonant contributions to di-Higgs production in the singlet extension of the Standard Model, where the additional heavy scalar provides a resonant channel. We find these interference contributions to have a non-negligible effect on the cross-sections and differential distributions. In order to allow for a computationally efficient treatment of these effects via reweighting, we introduce a new tool utilising a matrix-element reweighting method: HHReweighter. In addition to the broadly used di-Higgs invariant mass $m_{hh}$, we analyse the sensitivity to the interference terms for other kinematic variables, such as the Higgs boson transverse momentum, and find that these also can be sensitive to interference effects. Furthermore, we provide updates on the latest experimental and theoretical limits on the parameter space of the real singlet extension of the Standard Model Higgs sector., Comment: HHReweighter tool available as code at https://gitlab.com/danielwinterbottom/HHReweighter. 58 pages including appendix and references; 43 figures

We here report on the progress of the HHH Workshop, that took place in Dubrovnik in July 2023. After the discovery of a particle that complies with the properties of the Higgs boson of the Standard Model, all SM parameters are in principle determined. However, in order to verify or falsify the model, the full form of the potential has to be determined. This includes the measurement of the triple and quartic scalar couplings. We here report on ongoing progress of measurements for multi scalar final states, with an emphasis on three SM-like scalar bosons at 125 GeV, but also mentioning other options. We discuss both experimental progress and challenges as well as theoretical studies and models that can enhance such rates with respect to the SM predictions., Comment: 117 pages, 56 figures; Whitepaper resulting from HHH Workshop in Dubrovnik 2023, https://indico.cern.ch/event/1232581/; v2: small typos corrected

I briefly review the Benchmark Planes in the Two-Real-Singlet Model (TRSM), a model that enhances the Standard Model (SM) scalar sector by two real singlets that obey a Z2 x Z2' symmetry. All fields acquire a vacuum expectation value, that softly breaks the above symmetry and leads to mixing of all CP even neutral states. Furthermore, all interactions with SM-like particles are inherited from the SM-like doublet via mixing. I remind the readers of the previously proposed benchmark planes, and briefly discuss possible production at future Higgs factories, as well as regions in a more generic scan of the model. Results are based on previous work presented in arXiv:1908.08554, arXiv:2209.10996, and arXiv:2305.08595., Comment: 6 pages, 7 figures. Contribution to proceedings of "The European Physical Society Conference on High Energy Physics" 2023, Hamburg, Germany

I give a short summary on scenarios with new physics scalars that could be investigated at future $e^+e^-$ colliders. I concentrate on cases where at least one of the additional scalar has a mass below 125 GeV, and discuss both models where this could be realized, as well as studies which focus on such scenarios. This work is based on arXiv:2205.09687, and partial results were also presented in arXiv:2211.10231., Comment: 12 pages, 11 figures, Talk presented at the International Workshop on Future Linear Colliders (LCWS 2023), 15-19 May 2023. C23-05-15.3. arXiv admin note: substantial text overlap with arXiv:2205.09687, arXiv:2203.08210

I present an update on the the Benchmark Planes in the Two-Real-Singlet Model (TRSM), a model that enhances the Standard Model (SM) scalar sector by two real singlets, where an additional Z2 x Z2' symmetry is imposed. I discuss the case where all fields acquire a vacuum expectation value, such that the model contains in total 3 CP-even neutral scalars that can interact with each other. I remind the readers of the previously proposed benchmark planes, current constraints, and possible signatures at current and future colliders. This is an update for Moriond 2023 of results presented in arXiv:2209.10996., Comment: 4 pages, 4 figures; Contribution to the 2023 QCD session of the 57th Rencontres de Moriond

A muon collider would enable the big jump ahead in energy reach that is needed for a fruitful exploration of fundamental interactions. The challenges of producing muon collisions at high luminosity and 10~TeV centre of mass energy are being investigated by the recently-formed International Muon Collider Collaboration. This Review summarises the status and the recent advances on muon colliders design, physics and detector studies. The aim is to provide a global perspective of the field and to outline directions for future work., Comment: 118 pages, 103 figures

Although many suggestions for BSM searches at future colliders exist, most of them concentrate on additional scalars that have masses higher than the current SM scalar mass. I will give a short overview on the current status of models and searches for scalars with masses below this. This work is mainly based on arXiv:2203.08210, arXiv:2205.09687., Comment: 4 pages, 4 figures, contribution to proceedings of 41st International Conference on High Energy physics - ICHEP2022

The TRSM is a new physics model that extends the scalar sector of the Standard Model by two additional CP even scalars. It leads to a large variety of interesting signatures, some of which have not yet been explored by the LHC experiments. I will also discuss the option to explore the hhh final state within this model., Comment: 4 pages, 2 figures; proceedings of 41st International Conference on High Energy physics - ICHEP2022

I will briefly discuss the signatures and discovery prospects of several new physics models containing dark matter candidates at future lepton colliders. In particular, I will discuss the two models that, among other signatures, lead to electroweak gauge bosons and missing energy: the Inert Doublet Model, as well as the THDMa, a two Higgs doublet model with an additional pseudoscalar that serves as a portal to the dark sector. Results are mainly based on a Snowmass Whitepaper arXiv:2203.07913, Comment: 6 pages, 5 figures; contribution to the proceedings of the 41st International Conference on High Energy physics - ICHEP2022

In this proceeding, I discuss several models that extend the scalar sector of the Standard Model by additional matter states. I here focus on results for models with singlet extensions, which have been obtained recently and update some of the results presented in previous work. In more detail, I will briefly review the option to test a strong first-order electroweak phase transition using precision measurements in the electroweak sector, as well as production cross-sections for non-standard scalar production at Higgs factories., Comment: 13 pages, 11 figures; proceedings of the Eighth Workshop on Theory, Phenomenology and Experiments in Flavour Physics - FPCapri2022 -. arXiv admin note: substantial text overlap with arXiv:2209.10996

This is the Snowmass2021 Energy Frontier (EF) Beyond the Standard Model (BSM) report. It combines the EF topical group reports of EF08 (Model-specific explorations), EF09 (More general explorations), and EF10 (Dark Matter at Colliders). The report includes a general introduction to BSM motivations and the comparative prospects for proposed future experiments for a broad range of potential BSM models and signatures, including compositeness, SUSY, leptoquarks, more general new bosons and fermions, long-lived particles, dark matter, charged-lepton flavor violation, and anomaly detection., Comment: 108 pages + 38 pages references and appendix, 37 figures, Report of the Topical Group on Beyond the Standard Model Physics at Energy Frontier for Snowmass 2021. The first nine authors are the Conveners, with Contributions from the other authors

In this manuscript, I briefly review the Benchmark Planes in the Two-Real-Singlet Model (TRSM), a model that enhances the Standard Model (SM) scalar sector by two real singlets that obey a Z2 x Z2' symmetry. In this model, all fields acquire a vacuum expectation value, such that the model contains in total 3 CP-even neutral scalars that can interact with each other. All interactions with SM-like particles are inherited from the SM-like doublet via mixing. I remind the readers of the previously proposed benchmark planes, and briefly discuss possible production at future Higgs factories, as well as regions in a more generic scan of the model. For these, I also discuss the use of the W-boson mass as a precision observable to determine allowed/ excluded regions in the models parameter space. This work builds on a whitepaper submitted to the Snowmass process., Comment: 21 pages, 14 figures; extension of Whitepaper presented at arXiv:2205.14486; v2: slightly changed phrasing of abstract to clarify this is not a Snowmass Whitepaper; v3: minor changes, corresponds to published journal version

The precise measurement of physics observables and the test of their consistency within the standard model (SM) are an invaluable approach, complemented by direct searches for new particles, to determine the existence of physics beyond the standard model (BSM). Studies of massive electroweak gauge bosons (W and Z bosons) are a promising target for indirect BSM searches, since the interactions of photons and gluons are strongly constrained by the unbroken gauge symmetries. They can be divided into two categories: (a) Fermion scattering processes mediated by s- or t-channel W/Z bosons, also known as electroweak precision measurements; and (b) multi-boson processes, which include production of two or more vector bosons in fermion-antifermion annihilation, as well as vector boson scattering (VBS) processes. The latter categories can test modifications of gauge-boson self-interactions, and the sensitivity is typically improved with increased collision energy. This report evaluates the achievable precision of a range of future experiments, which depend on the statistics of the collected data sample, the experimental and theoretical systematic uncertainties, and their correlations. In addition it presents a combined interpretation of these results, together with similar studies in the Higgs and top sector, in the Standard Model effective field theory (SMEFT) framework. This framework provides a model-independent prescription to put generic constraints on new physics and to study and combine large sets of experimental observables, assuming that the new physics scales are significantly higher than the EW scale., Comment: 55 pages; Report of the EF04 topical group for Snowmass 2021; v2: few typos corrected and references added

I give a short overview on di-Higgs productions in models that extend the Standard Model of particle physics by additional fields and particle content, including EFT prescriptions., Comment: 6 pages, 4 figures, contribution to the proceedings of "The Tenth Annual Conference on Large Hadron Collider Physics" (LHCP2022); v2: Some comments added regarding EFT benchmark clusters. Corresponds to accepted proceedings version

In this whitepaper, I briefly review the Benchmark Planes in the Two-Real-Singlet Model (TRSM), a model that enhances the Standard Model (SM) scalar sector by two real singlets that obey a $\mathbb{Z}_2\,\otimes\,\mathbb{Z}_2'$ symmetry. In this model, all fields acquire a vacuum expectation value, such that the model contains in total 3 CP-even neutral scalars that can interact with each other. All interactions with SM-like particles are inherited from the SM-like doublet via mixing. I remind the readers of the previously proposed benchmark planes, and briefly discuss possible production at future Higgs factories., Comment: 14 pages, 7 figures; contribution to Snowmass 2021

We consider an extension of the scalar sector of the Standard Model (SM) by an additional gauge singlet, which mixes with a part of the SM-like Higgs doublet. Within this model, parameter-space regions exist that can lead to a strong first-order electro-weak phase transition, a necessary condition for electro-weak baryogenesis. We discuss how such regions of the parameter space can be tested using the SM-like Higgs boson's signal strength measurements, as well as precision observables, such as e.g. the W-boson mass, at current and future colliders., Comment: 8 pages, 1 figure; contribution to Snowmass 2021. Minor correction to v1

In this manuscript, I give a short summary on scenarios with new physics scalars that could be investigated at future $e^+e^-$ colliders. I concentrate on cases where at least one of the additional scalar has a mass below 125 GeV, and discuss both models where this could be realized, as well as studies which focus on such scenarios. This work is based on several overview talks I recently gave at the CEPC workshop, FCC week and ECFA future collider workshop, as well as a Snowmass White Paper., Comment: 22 pages, 20 figures; largely builds on arXiv:2203.08210. Will be published in the special issue of Universe "Higgs and BSM Physics: 10th Anniversary of the Discovery of the Higgs Boson"

I give an overview on models that extend the Standard Model scalar sector by additional gauge singlets or multiplets. I discuss current constraints on such models, as well as possible signatures and discovery prospects at current and future colliders., Comment: 8 pages, 6 figures; Contribution to the 2022 EW session of the 56th Rencontres de Moriond. arXiv admin note: text overlap with arXiv:2203.17016, arXiv:1908.10809

I here discuss the THDMa, a type II two Higgs doublet model that is enhanced by an additional pseudoscalar which serves as a portal to the dark matter sector containing a fermionic dark matter andidate. I present a recent scan of the models parameter space where all parameters are allowed to float freely, and discuss prospects for this model at future $e^+e^-$ colliders for cases that are not covered in standard THDM searches., Comment: 6 pages, 3 figures; Talk presented at the 30th International Symposium on Lepton Photon Interactions at High Energies, hosted by the University of Manchester, 10-14 January 2022

In this proceeding, I summarize results on various new physics extensions of the Standard Model, for models with and without dark matter candidates. I discuss current constraints as well as rates and discovery prospects at future colliders., Comment: 12 pages, 7 figures, contribution to Corfu Summer Institute 2021 "School and Workshops on Elementary Particle Physics and Gravity". arXiv admin note: text overlap with arXiv:2202.09636

Two models that extend the particle content of the SM and provide dark matter candidates, namely the Inert Doublet Model and the Two-Higgs Doublet model with additional pseudoscalar, are confronted with current experimental and theoretical constraints and predictions for production cross sections for various standard pair-production modes within these models at future lepton colliders are presented., Comment: 15 pages, 9 figures; contribution to Snowmass 2021

In this whitepaper, I give a short summary on possible channels of low-mass scenarios and their discovery potential at future $e^+e^-$ colliders. This is a summary of talks I recently gave at the CEPC workshop, FCC week and ECFA future collider workshop., Comment: 19 pages, 19 figures; contribution to Snowmass 2021. Comments welcome

The International Linear Collider (ILC) is on the table now as a new global energy-frontier accelerator laboratory taking data in the 2030s. The ILC addresses key questions for our current understanding of particle physics. It is based on a proven accelerator technology. Its experiments will challenge the Standard Model of particle physics and will provide a new window to look beyond it. This document brings the story of the ILC up to date, emphasizing its strong physics motivation, its readiness for construction, and the opportunity it presents to the US and the global particle physics community., Comment: 356 pages, Large pdf file (40 MB) submitted to Snowmass 2021; v2 references to Snowmass contributions added, additional authors; v3 references added, some updates, additional authors

In the path towards a muon collider with center of mass energy of 10 TeV or more, a stage at 3 TeV emerges as an appealing option. Reviewing the physics potential of such muon collider is the main purpose of this document. In order to outline the progression of the physics performances across the stages, a few sensitivity projections for higher energy are also presented. There are many opportunities for probing new physics at a 3 TeV muon collider. Some of them are in common with the extensively documented physics case of the CLIC 3 TeV energy stage, and include measuring the Higgs trilinear coupling and testing the possible composite nature of the Higgs boson and of the top quark at the 20 TeV scale. Other opportunities are unique of a 3 TeV muon collider, and stem from the fact that muons are collided rather than electrons. This is exemplified by studying the potential to explore the microscopic origin of the current $g$-2 and $B$-physics anomalies, which are both related with muons., Comment: 73 pages, 28 figures; Contribution to Snowmass 2021

The perspective of designing muon colliders with high energy and luminosity, which is being investigated by the International Muon Collider Collaboration, has triggered a growing interest in their physics reach. We present a concise summary of the muon colliders potential to explore new physics, leveraging on the unique possibility of combining high available energy with very precise measurements., Comment: 21 pages, 7 figures; Contribution to Snowmass 2021

I discuss the allowed parameter space as well as collider prospects of several new physics models containing (broken) Z2 symmetries. I focus on effects of current constraints on these, and touch on several future collider options., Comment: 6 pages, 3 figures, 2 tables; proceedings of Discrete 2020-2021; v2: one abbreviation added, some publication information added. Corresponds to accepted proceedings version

We discuss two models that extend the Standard Model by additional particles, leading to additional scalar states, and also providing dark matter candidates. We briefly review the current constraints and comment on production cross sections at present and future collider facilities., Comment: 6 pages, 3 figures; contribution to proceedings of The European Physical Society Conference on High Energy Physics (EPS-HEP2021)

The THDMa is a new physics model that extends the scalar sector of the Standard Model by an additional doublet as well as a pseudoscalar singlet and allows for mixing between all possible scalar states. In the gauge-eigenbasis, the additional pseudoscalar serves as a portal to the dark sector, with a priori any dark matter spins states. The option where dark matter is fermionic is currently one of the standard benchmarks for the experimental collaborations, and several searches at the LHC constrain the corresponding parameter space. However, most current studies constrain regions in parameter space by setting all but 2 of the 12 free parameters to fixed values. In this work, we perform a generic scan on this model, allowing all parameters to float. We apply all current theoretical and experimental constraints, including bounds from current searches, recent results from B-physics, in particular B_s -> X_s gamma, as well as bounds from astroparticle physics. We identify regions in the parameter space which are still allowed after these have been applied and which might be interesting for an investigation at current and future collider machines., Comment: 30 pages, 8 figures; v2: 33 pages, 8 figures, corresponds to published journal version (slight style differences)

After the discovery of a particle that complies with the properties of the Higgs boson predicted by the Standard Model, particle physics has entered an exciting era. One important question is whether the scalar sector realized by Nature indeed corresponds to the one predicted by the SM, or whether the resonance at 125 GeV is a manifestation of a more extended scalar sector, and additional scalar states could be observed at current or future collider facilities., Comment: 6 pages, 3 figures; Contribution to the 2021 QCD session of the 55th Rencontres de Moriond

We here present preliminary results on a parameter scan of the THDMa, a new physics model that extends the scalar sector of the Standard Model by an additional doublet as well as a pseudoscalar singlet. In the gauge-eigenbasis, the additional pseudoscalar serves as a portal to the dark sector, with a fermionic dark matter candidate. This model is currently one of the standard benchmarks for the LHC experimental collaborations. We apply all current theoretical and experimental constraints and identify regions in the parameter space that might be interesting for an investigation at possible future $e^+e^-$ facilities., Comment: 14 pages, 7 figure; Talk presented at the International Workshop on Future Linear Colliders (LCWS2021), 15-18 March 2021. C21-03-15.1

After the discovery of the Higgs boson in 2012, particle physics has entered an exciting era. An important question is whether the Standard Model of particle physics correctly describes the scalar sector realized by nature, or whether it is part of a more extended model, featuring additional particle content. A prime way to test this is to probe models with extended scalar sectors at future collider facilities. We here discuss such models in the context of high-luminosity LHC, a possible proton-proton collider with 27 and 100 TeV center-of-mass energy, as well as future lepton colliders with various center-of-mass energies., Comment: 20 pages, 8 figures; Presented at XXVII Cracow EPIPHANY Conference of Future of particle physics

We investigate the production of three Higgs bosons in the Two Real Singlet extension of the Standard Model, where the scalar sector is augmented by two additional real scalar fields which are singlets under the Standard Model gauge group. The model contains three neutral CP-even scalars, allowing for resonant production and asymmetric decay chains. We focus on the signature $p p\,\rightarrow\,h_3\,\rightarrow\,h_1\,h_2\,\rightarrow\,h_1\,h_1\,h_1$, where we identify $h_3$ as the heaviest scalar state, $h_2$ as the second heaviest and the lightest, $h_1$, as the Standard Model-like Higgs boson discovered by the Large Hadron Collider experiments. The dominant final state occurs when all three Higgs bosons decay to bottom-anti-bottom quark pairs, $h_1\,\rightarrow\,b\,\bar{b}$, leading to 6 $b$-jets. Taking into account all current theoretical and experimental constraints, we determine the discovery prospects for this channel in future runs of the Large Hadron Collider, as well as in the high-luminosity phase., Comment: 29 pages, 2 figures. Matches published version

We present cross-section expectations for various processes and collider options, for benchmark scenarios of the Inert Doublet Model, a Two Higgs Doublet Model with a dark matter candidate. The proposed scenarios are consistent with current dark matter constraints, including the most recent bounds from the XENON1T experiment and relic density, as well as with known collider and low-energy limits. These benchmarks, chosen in earlier work for studies at $e^+e^-$ colliders, exhibit a variety of kinematic features that should be explored at current and future runs of the LHC. We provide cross sections for all relevant production processes at 13 TeV, 27 TeV and 100 TeV proton collider, as well as for a possible 10 TeV and 30 TeV muon collider., Comment: 44 pages, 11 figures; v2: corresponds to published journal version (slight style differences)

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

The Inert Doublet Model (IDM) is one of the simplest extensions of the Standard Model (SM), providing a dark matter candidate. It is a two Higgs doublet model with a discrete $Z_2$ symmetry, that prevents the scalars of the second doublet (inert scalars) from coupling to the SM fermions and makes the lightest of them stable. We study a large number of IDM scenarios, which are consistent with current constraints on direct detection and relic density of dark matter, as well as with all collider and low-energy limits. We propose a set of benchmark points with different kinematic features, that promise detectable signals at future $e^+e^-$ colliders. Two inert scalar pair-production processes are considered, $e^+e^- \to A~H $ and $e^+e^- \to H^+H^-$, followed by decays of $A$ and $H^\pm$ into final states which always include the lightest and stable neutral scalar dark matter candidate $H$. Significance of the expected observations is studied for different benchmark models and different running scenarios, for centre-of-mass energies from 250 GeV up to 3 TeV. For low mass scenarios, high significance can be obtained for the signal signatures with two muons or an electron and a muon in the final state. For high mass scenarios, which are only accessible at high energy stages of CLIC, the significance is too low for the leptonic signature and the semi-leptonic final state has to be used as the discovery channel. Results presented for this channel are based on the fast simulation of the CLIC detector response with the DELPHES package., Comment: Talk presented at the International Workshop on Future Linear Colliders (LCWS2019), Sendai, Japan, 28 October-1 November, 2019. C19-10-28. arXiv admin note: substantial text overlap with arXiv:1908.04659

The Inert Doublet Model (IDM) is one of the simplest extensions of the Standard Model (SM), providing a dark matter candidate. It is a two Higgs doublet model with a discrete $Z_2$ symmetry, that prevents the scalars of the second doublet (inert scalars) from coupling to the SM fermions and makes the lightest of them stable. We study a large group of IDM scenarios, which are consistent with current constraints on direct detection, including the most recent bounds from the XENON1T experiment and relic density of dark matter, as well as with all collider and low-energy limits. We propose a set of benchmark points with different kinematic features, that promise detectable signals at future $e^+e^-$ colliders. Two inert scalar pair-production processes are considered, $e^+e^- \to H^+H^-$ and $e^+e^- \to AH$, followed by decays of $H^\pm$ and $A$ into final states which include the lightest and stable neutral scalar dark matter candidate $H$. Significance of the expected observations is studied for different benchmark models and different running scenarios, for centre-of-mass energies up to 3 TeV. Numerical results are presented for the signal signatures with two muons or an electron and a muon in the final state. For high mass scenarios, when the significance is too low for the leptonic signatures, the semi-leptonic signature can be used as the discovery channel., Comment: 7 pages, Proceedings for European Physical Society Conference on High Energy Physics - EPS-HEP2019, 10-17 July, 2019, Ghent, Belgium, based on 1809.07712, 1811.06952. arXiv admin note: text overlap with arXiv:1908.04659

In this work, I briefly report on constraints that can be obtained on new physics models that extend the scalar sector of the Standard Model (SM) of particle physics at the LHC. I concentrate on a few simple examples which serve to demonstrate advantages as well as possible drawbacks of current experimental searches, and comment on the discovery prospects of such models at future colliders., Comment: 16 pages, 6 figures. Contribution to Proceedings of 7th Edition of the Large Hadron Collider Physics Conference (LHCP2019) in Puebla, Mexico; will be published as PoS(LHCP2019)138

We investigate the LHC phenomenology of a model where the Standard Model (SM) scalar sector is extended by two real scalar singlets. A $\mathbb{Z}_2\otimes\mathbb{Z}_2'$ discrete symmetry is imposed to reduce the number of scalar potential parameters, which is spontaneously broken by the vacuum expectation values of the singlet fields. As a result, all three neutral scalar fields mix, leading to three neutral CP-even scalar bosons, out of which one is identified with the observed Higgs boson at 125 GeV. We explore all relevant collider signatures of the three scalars in this model. Besides the single production of a scalar boson decaying directly to SM particle final states, we extensively discuss the possibility of resonant multi-scalar production. The latter includes decays of the produced scalar boson to two identical scalars ("symmetric decays"), as well as to two different scalars ("asymmetric decays"). Furthermore, we discuss the possibility of successive decays to the lightest scalar states ("cascade decays"), which lead to experimentally spectacular three- and four-Higgs final states. We provide six benchmark scenarios for detailed experimental studies of these Higgs-to-Higgs decay signatures., Comment: 36 pages, 15 figures, data for the benchmark scenarios available upon request, text updated to match published version

The Inert Doublet Model is one of the simplest extensions of the Standard Model, providing a dark matter candidate. It is a two Higgs doublet model with a discrete $Z_2$ symmetry, that prevents the scalars of the second doublet (inert scalars) from coupling to the Standard Model fermions and makes the lightest of them stable. We study a large number of Inert Doublet Model scenarios, which are consistent with current constraints on direct detection, including the most recent bounds from the XENON1T experiment and relic density of dark matter, as well as collider and low-energy limits. We use a set of benchmark points with different kinematic features, that promise detectable signals at future $e^+e^-$ colliders. Two inert scalar pair-production processes are considered, $e^+e^- \to A~H $ and $e^+e^- \to H^+H^-$, followed by decays of $H^\pm$ and $A$ into the final states which include the lightest and stable neutral scalar dark matter candidate $H$. Significance of the expected observations is studied for different benchmark models and different running scenarios, for centre-of-mass energies up to 3 TeV. Numerical results are presented for the signal signatures with two muons or an electron and a muon in the final state, while the qualitative conclusions can also be drawn for the semi-leptonic signatures., Comment: 6 pages, 9 figures, submitted to proceedings of ALPS'2019

We discuss the status of the Inert Doublet Model, a two-Higgs doublet model that obeys a discrete Z2 symmetry and provides a dark matter candidate. We discuss all current theoretical and experimental constraints on the model as well as discovery prospects at current and future colliders., Comment: 6 pages, 3 figures; to be published in the proceedings of DISCRETE2018: 6th Symposium on Prospects in the Physics of Discrete Symmetries, Vienna, 26.-30.11.18; v2: minor changes; corresponds to accepted proceedings version

In this work, we use a recast of the Run II search for invisible Higgs decays within Vector Boson Fusion to constrain the parameter space of the Inert Doublet model, a two Higgs doublet model with a dark matter candidate. When including all known theoretical as well as collider constraints, we find that the above can rule out a relatively large part in the mH-lambda345 parameter space, for dark scalar masses mH <= 100 GeV. Including the latest dark matter constraints, a smaller part of parameter space remains which is solely excluded from the above analysis. We also discuss the sensitivity of monojet searches and multilepton final states from Run II., Comment: 29 pages, 7 figures, 6 tables; v2: slight modifications, some references added. Corresponds to published journal version

We investigate the prospect of discovering the Inert Doublet Model scalars at CLIC. As signal processes, we consider the pair-production of inert scalars, namely e+e- -> H+H- and e+e- -> AH, followed by decays of charged scalars H+ and neutral scalars A into leptonic final states and missing transverse energy. We focus on signal signatures with two muons or an electron and a muon pair in the final state. A number of selected benchmark scenarios that cover the range of possible collider signatures of the IDM are considered. For the suppression of SM background with the same visible signature, multivariate analysis methods are employed. For several benchmark points discovery is already possible at low-energy stage of CLIC. Prospects of investigating scenarios that are only accessible at higher collider energies are also discussed., Comment: latex, 22 pages, 12 figures, v2: comments on indirect DM searches and LHC prospects added, matches published version

Dark matter (DM) simplified models are by now commonly used by the ATLAS and CMS Collaborations to interpret searches for missing transverse energy ($E_T^\mathrm{miss}$). The coherent use of these models sharpened the LHC DM search program, especially in the presentation of its results and their comparison to DM direct-detection (DD) and indirect-detection (ID) experiments. However, the community has been aware of the limitations of the DM simplified models, in particular the lack of theoretical consistency of some of them and their restricted phenomenology leading to the relevance of only a small subset of $E_T^\mathrm{miss}$ signatures. This document from the LHC Dark Matter Working Group identifies an example of a next-generation DM model, called $\textrm{2HDM+a}$, that provides the simplest theoretically consistent extension of the DM pseudoscalar simplified model. A comprehensive study of the phenomenology of the $\textrm{2HDM+a}$ model is presented, including a discussion of the rich and intricate pattern of mono-$X$ signatures and the relevance of other DM as well as non-DM experiments. Based on our discussions, a set of recommended scans are proposed to explore the parameter space of the $\textrm{2HDM+a}$ model through LHC searches. The exclusion limits obtained from the proposed scans can be consistently compared to the constraints on the $\textrm{2HDM+a}$ model that derive from DD, ID and the DM relic density., Comment: Change of CERN report ID in v2

We present benchmarks for the Inert Doublet Model, a Two Higgs Doublet Model with a dark matter candidate. They are consistent with current constraints on direct detection, including the most recent bounds from the XENON1T experiment and relic density of dark matter, as well as with known collider and low-energy limits. We focus on parameter choices that promise detectable signals at lepton colliders via pair-production of H+H- and HA. For these we choose a large variety of benchmark points with different kinematic features, leading to distinctly different final states in order to cover the large variety of collider signatures that can result from the model., Comment: 21 pages, 1 figure, 5 tables; v2: corresponds to published version. Comments on future prospects added

We give a brief overview of beyond the Standard Model (BSM) theories with an extended scalar sector and their phenomenological status in the light of recent experimental results. We discuss the relevant theoretical and experimental constraints, and show their impact on the allowed parameter space of two specific models: the real scalar singlet extension of the Standard Model (SM) and the Inert Doublet Model. We emphasize the importance of the LHC measurements, both the direct searches for additional scalar bosons, as well as the precise measurements of properties of the Higgs boson of mass 125 GeV. We show the complementarity of these measurements to electroweak and dark matter observables., Comment: 18 pages, 8 figures; prepared for submission to MPLA (invited review) v2: several references and small text modification added to align with journal version. 2 small errors in plots corrected

In this note, we discuss recent updates to a previous scan for the Inert Doublet Model, a two Higgs doublet model with a dark matter candidate. We explicitly show the inclusion of updated constraints on direct detection reduces the allowed parameter space significantly. We furthermore discuss the IDMS - an extension of the IDM with a complex singlet., Comment: 12 pages, 7 figures; Contribution to Corfu Summer Institute 2016 "School and Workshops on Elementary Particle Physics and Gravity", 31 August - 23 September, 2016, Corfu, Greece