In many theories of physics beyond the Standard Model, from extra dimensions to Hidden Valleys and models of dark matter, Z' bosons mediate between Standard Model particles and hidden sector states. We study the feasibility of observing such hidden states through an invisibly decaying Z' at the LHC. We focus on the process pp -> γZ' -> γX X*, where X is any neutral, (quasi-) stable particle, whether a Standard Model (SM) neutrino or a new state. This complements a previous study using pp -> Z Z' -> l+ l- X X*. Only the Z' mass and two effective charges are needed to describe this process. If the Z' decays invisibly only to Standard Model neutrinos, then these charges are predicted by observation of the Z' through the Drell-Yan process, allowing discrimination between Z' decays to SM neutrinos and invisible decays to new states. We carefully discuss all backgrounds and systematic errors that affect this search. We find that hidden sector decays of a 1 TeV Z' can be observed at 5 sigma significance with 50 fb^{-1} at the LHC. Observation of a 1.5 TeV state requires super-LHC statistics of 1 ab^{-1}. Control of the systematic errors, in particular the parton distribution function uncertainty of the dominant Z γbackground, is crucial to maximize the LHC search
In this note, we explore the Tevatron and LHC detection prospects for a nonstandard Higgs whose decays contain both missing and visible energy. In particular, we consider the decay $h \to χ_2 χ_1$ where $χ_1$ is stable and $χ_2$ decay back to $χ_1$ and additional visible particles. We focus on adapting standard searches for both Higgses and supersymmetry to these decays. In these channels, the Tevatron has little reach, but the LHC has good prospects for decays that involve leptons or neutrinos. In particular, the standard WW* search for a Higgs produced in vector boson fusion has the largest …
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…
Many models of electroweak symmetry breaking have an additional light pseudoscalar. If the Higgs boson can decay to a new pseudoscalar, LEP searches for the Higgs can be significantly altered and the Higgs can be as light as 86 GeV. Discovering the Higgs boson in these models is challenging when the pseudoscalar is lighter than 10 GeV because it decays dominantly into tau leptons. In this paper, we discuss discovering the Higgs in a subdominant decay mode where one of the pseudoscalars decays to a pair of muons. This search allows for potential discovery of a cascade-decaying Higgs boson with …
We review the pair-production and decay of selectrons in $e^-e^-$ collisions and show how the standard model backgrounds can be virtually eliminated with polarized beams. The exceedingly simple analysis involved and the large sample of background-free supersymmetric events make this linear collider operating mode ideal for discovering selectrons and measuring the mass of the lightest neutralino.
The recent observation of discrepancies in the muonic sector motivates searches for the yet undiscovered atom true muonium $(μ^+μ^-)$. To leverage potential experimental signals, precise theoretical calculations are required. I will present the on-going work to compute higher-order corrections to the hyperfine splitting and the Lamb shift. Further, possible detection in rare meson decay experiments like REDTOP and using true muonium production to constrain mesonic form factors will be discussed.
The LHC has delivered several fb-1 of data in spring and summer 2011, opening new windows of opportunity for discovering phenomena beyond the Standard Model. A summary of the searches conducted by the ATLAS and CMS experiments based on about 1 fb-1 of data is presented.
The Twin Higgs mechanism keeps the scalar sector of the Standard Model (SM) natural while remaining consistent with the non-observation of new colored particles at the Large Hadron Collider (LHC). In this construction the heavy twin Higgs boson provides a portal between the SM particles and the twin sector, but is quite challenging to discover at colliders. In the Fraternal Twin Higgs setup, where light twin quarks are absent, we study a novel discovery channel for the heavy twin Higgs boson by considering its decay to a pair of light Higgs bosons, one of which subsequently decays to glueball …
The physics potential of discovering and exploring supersymmetry at future e^+e^- linear colliders is reviewed. Such colliders are planned to start to operate at a center-of-mass energy of 500 GeV to 800 GeV, with a final energy of about 2 TeV expected. They are ideal facilities for the discovery of supersymmetric particles. High precision measurements of their properties and interactions will help to uncover the mechanism of supersymmetry breaking and will allow for tests of grand unification scenarios.
We show how weakly supervised machine learning can improve the sensitivity of LHC mono-jet searches to new physics models with anomalous jet dynamics. The Classification Without Labels (CWoLa) method is used to extract all the information available from low-level detector information without any reference to specific new physics models. For the example of a strongly interacting dark matter model, we employ simulated data to show that the discovery potential of an existing generic search can be boosted considerably.
This letter presents new results on the combined sensitivity of the LHC and underground dark matter search experiments to the lightest neutralino as WIMP candidate in the minimal Supersymmetric extension of the Standard Model. We show that monojet searches significantly extend the sensitivity to the neutralino mass in scenarios where scalar quarks are nearly degenerate in mass with it. The inclusion of the latest bound by the LUX experiment on the neutralino-nucleon spin-independent scattering cross section expands this sensitivity further, highlighting the remarkable complementarity of jets/$…
We explore the mono-$Z$ signature for dark matter searches at future high energy $e^+e^-$ colliders. In the context of effective field theory, we consider two kinds of contact operators describing dark matter interactions with electroweak gauge bosons and with electron/positron, respectively. For five benchmark models, we propose kinematic cuts to distinguish signals from backgrounds for both charged leptonic and hadronic decay modes of the $Z$ boson. We also present the experimental sensitivity to cutoff scales of effective operators and compare it with that of the Fermi-LAT indirect search a…
Mono-X searches are standard dark matter search strategies at the LHC. First, we show how in the case of initial state radiation they essentially collapse to mono-jet searches. Second, we systematically study mono-X signatures from decays of heavier dark matter states. Direct detection constraints strongly limit our MSSM expectations, but largely vanish for mono-Z and mono-Higgs signals once we include light NMSSM mediators. Finally, the decay topology motivates mono-W-pair and mono-Higgs-pair searches, strengthening and complementing their mono-X counterparts.
We study the discrimination of quark-initiated jets from gluon-initiated jets in monojet searches for dark matter using the technique of averaged jet energy profiles. We demonstrate our results in the context of effective field theories of dark matter interactions with quarks and gluons, but our methods apply more generally to a wide class of models. Different effective theories of dark matter and the standard model backgrounds each have a characteristic quark/gluon fraction for the leading jet. When used in conjunction with the traditional cut-and-count monojet search, the jet energy profile …
We consider minimal dark matter scenarios featuring momentum-dependent couplings of the dark sector to the Standard Model. We derive constraints from existing LHC searches in the monojet channel, estimate the future LHC sensitivity for an integrated luminosity of 300 fb$^{-1}$, and compare with models exhibiting conventional momentum-independent interactions with the dark sector. In addition to being well motivated by (composite) pseudo-Goldstone dark matter scenarios, momentum-dependent couplings are interesting as they weaken direct detection constraints. For a specific dark matter mass, the…
We study collider signatures of a class of dark matter models with a GeV-scale dark Z'. At hadron colliders, the production of dark matter particles naturally leads to associated production of the Z', which can appear as a narrow jet after it decays hadronically. Contrary to the usual mono-jet signal from initial state radiation, the final state radiation of dark matter can generate the signature of a mono-Z' jet plus missing transverse energy. Performing a jet-substructure analysis to tag the Z' jet, we show that these Z' jets can be distinguished from QCD jets at high significance. Compared …
Recently, there have been proposals that the classic Euler-Heisenberg Lagrangian together with duality could be employed to set limits on magnetic monopoles having masses less than 1 TeV. The D0 collaboration at Fermilab has used such a proposal to set mass limits based on the nonobservation of pairs of photons each with high transverse momentum. In this note, we critique the underlying theory, by showing that at the quoted limits the cross section violates unitarity and is unstable with respect to radiative corrections. It is proposed that the correct coupling of magnetic monopoles to photons…
We present theoretical predictions for mono-$Z$ production in the search for dark matter in Run-II at the LHC, including next-to-leading order QCD corrections and parton-shower effects. We consider generic simplified models with vector and scalar $s$-channel mediators. The calculation is performed by implementing the simplified models in the FeynRules/MadGraph5_aMC@NLO framework, which allows us to include higher-order QCD corrections and parton-shower effects in an automated way. We find that these corrections are sizeable and help to reduce the theoretical uncertainties. We also investigate …
We study the potential of the LHCb experiment to discover, for the first time, the $μ^+μ^-$ true muonium bound state. We propose a search for the vector $1^3S_1$ state, $\mathcal{T\!M}$, which kinetically mixes with the photon and dominantly decays to $e^+e^-$. We demonstrate that a search for $η\to γ\mathcal{T\!M}$, $\mathcal{T\!M}\to e^+e^-$ in a displaced vertex can exceed a significance of 5 standard deviations assuming statistical uncertainties. We present two possible searches: an inclusive search for the $e^+e^-$ vertex, and an exclusive search which requires an additional photon and a …
The Standard Model (SM) of the microcosm provides an excellent description of the phenomena of the microcosm, with the triumph of the discovery of the Higgs boson. There are many reasons, however, to believe that the SM is incomplete and represents a valid theory at relatively low energies only. Of particular interest are the models based on complete symmetries, such as those attempting a true unification between leptons and quarks in terms of a single symmetry group (Grand Unified Theories, GUTs) and those attempting unification between fermions and bosons, such as the supersymmetry. This cha…
As any e$^+$e$^-$ scattering process can be accompanied by a hard photon emission from the initial state radiation, the analysis of the energy spectrum and angular distributions of those photons can be used to search for hard processes with an invisible final state. Thus high energy e$^+$e$^-$ colliders offer a unique possibility for the most general search of Dark matter based on the mono-photon signature. We consider production of DM particles via a mediator at the International Linear Collider (ILC) and Compact Linear Collider (CLIC) experiments taking into account detector effects within t…
We consider the use of directionality in the search for monoenergetic sub-GeV neutrinos arising from the decay of stopped kaons, which can be produced by dark matter annihilation in the core of the Sun. When these neutrinos undergo charged-current interactions with a nucleus at a neutrino detector, they often eject a proton which is highly peaked in the forward direction. The direction of this track can be measured at DUNE, allowing one to distinguish signal from background by comparing on-source and off-source event rates. We find that directional information can enhance the signal to backgro…
We evaluate the discovery probability of a combined analysis of proposed neutrinoless double-beta decay experiments in a scenario with normal ordered neutrino masses. The discovery probability strongly depends on the value of the lightest neutrino mass, ranging from zero in case of vanishing masses and up to 80-90\% for values just below the current constraints. We study the discovery probability in different scenarios, focusing on the exciting prospect in which cosmological surveys will measure the sum of neutrino masses. Uncertainties in nuclear matrix element calculations partially compensa…
We consider LHC searches for dark matter in the mono-Higgs channel using the tools of effective field theory. This channel takes unique advantage of the presence of $SU(2)_L$ breaking in those operators to avoid the need for any initial-state radiation, usually necessary to tag the production of invisible particles. We find that sensitivities to parameters describing dark matter interactions with standard model particles are comparable to those from monojet searches for a subset of the usually-considered operators, and we present for the first time bounds from collider searches on operators wh…
In the near future, neutrino telescopes are expected to improve their sensitivity to the flux of monochromatic neutrinos produced by dark matter (DM) in our galaxy. This is illustrated by a new limit on the corresponding cross section that we derive from public IceCube data. In this context, we study which DM models could produce an observable flux of monochromatic neutrinos from DM annihilations. To this end, we proceed in two steps. First, within a set of simple and minimal assumptions concerning the properties of the DM particle, we determine the models that could give rise to a significant…
The LHC did not discover new particles beyond the Standard Model Higgs boson at 7 and 8 TeV, or in the first data samples at 13 TeV. However, the complementary nature of physics with $e^+e^-$ collisions still offers many interesting scenarios in which new particles can be discovered at the ILC. These scenarios take advantage of the capability of $e^+e^-$ collisions to observe particles with missing energy and small mass differences, to observe mono-photon events with precisely controlled backgrounds, and to observe the full range of exotic decay modes of the Higgs boson. The searches that an $…
We introduce a Minimal Simplified Dark Matter (MSDM) framework to quantitatively characterise dark matter (DM) searches at the LHC. We study two MSDM models where the DM is a Dirac fermion which interacts with a vector and axial-vector mediator. The models are characterised by four parameters: the DM and mediator masses, and the mediator couplings to DM and quarks. The MSDM models accurately capture the full event kinematics, and the dependence on all masses and couplings can be systematically studied. The interpretation of mono-jet searches in this framework can be used to establish an equal-…
We assess the current coverage and the future discovery potential of LHC searches for heavy Higgs bosons decaying into long-lived particles (LLPs), focusing primarily on the production of pairs of LLPs with hadronic final states. These signatures are generic in dark sectors where a heavy scalar decays into pairs of lighter states which subsequently mix with the Standard Model Higgs. We show that a handful of existing analyses provide broad coverage of LLP decay lengths ranging from millimeters to tens of meters, and explore the complementarity between searches for displaced and prompt final st…
High energy e$^+$e$^-$ colliders offer unique possibility for the most general dark matter search based on the mono-photon signature. Analysis of the energy spectrum and angular distributions of photons from the initial state radiation can be used to search for hard processes with invisible final state production. Most studies in the past focused on scenarios assuming heavy mediator exchange. We notice however, that scenarios with light mediator exchange are still not excluded by existing experimental data, if the mediator coupling to Standard Model particles is very small. We proposed a novel…
In supersymmetric models, Winos, partners of the SU(2) gauge bosons, may be the lightest supersymmetric particles (LSPs). For generic parameters, charged and neutral Winos are highly degenerate. Charged Winos travel macroscopic distances, but can decay to neutral Winos and extremely soft leptons or pions before reaching the muon chambers, thereby circumventing conventional trigger requirements based on energetic decay products or muon chamber hits. However, these charginos are detectable, and can be triggered on when produced in association with jets. In addition, we propose a new trigger for …
In this article, we explore the interplay between searches for supersymmetric particles and Higgs bosons at hadron colliders (the Tevatron and the LHC) and direct dark matter searches (such as CDMS, ZEPLIN, XENON, EDELWEISS, CRESST, WARP and others). We focus on collider searches for heavy MSSM Higgs bosons ($A$, $H$, $H^{\pm}$) and how the prospects for these searches are impacted by direct dark matter limits and vice versa. We find that the prospects of these two experimental programs are highly interrelated. A positive detection of $A$, $H$ or $H^{\pm}$ at the Tevatron would dramatically en…
The constrained Next-to-Minimal Supersymmetric Standard Model (cNMSSM) with mSugra-like boundary conditions at the GUT scale implies a singlino-like LSP with a mass just a few GeV below a stau NLSP. Hence, most of the squark/gluino decay cascades contain two tau leptons. The gluino mass >~ 1.2 TeV is somewhat larger than the squark masses of >~ 1 TeV. We simulate signal and background events for such a scenario at the LHC, and propose cuts on the transverse momenta of two jets, the missing transverse energy and the transverse momentum of a hadronically decaying tau lepton. This dedicated analy…
We derive the most general sets of viable mass spectra of the exotic Higgs bosons in the Georgi-Machacek model that are consistent with the theoretical constraints of vacuum stability and perturbative unitarity and the experimental constraints of electroweak precision observables, $Zb \bar b$ coupling and Higgs boson signal strengths. Branching ratios of various cascade decay channels of the doubly-charged Higgs boson in the ${\bf 5}$ representation, the singly-charged Higgs boson in ${\bf 3}$, and the singlet Higgs boson are further computed. As one of the most promising channels for discover…
We consider simplified models for dark matter (DM) at the LHC, focused on mono-Higgs, -Z, or -b produced in the final state. Our primary purpose is to study the LHC reach of a relatively complete set of simplified models for these final states, while comparing the reach of the mono-X DM search against direct searches for the mediating particle. We find that direct searches for the mediating particle, whether in di-jets, jets+MET, multi-b+MET, or di-boson+MET, are usually stronger. We draw attention to the cases that the mono-X search is strongest, which include regions of parameter space in in…
If pairs of new colored particles are produced at the Large Hadron Collider, determining their quantum numbers, and even discovering them, can be non-trivial. We suggest that valuable information can be obtained by measuring the resonant signals of their near-threshold QCD bound states. If the particles are charged, the resulting signatures include photons and leptons and are sufficiently rich for unambiguously determining their various quantum numbers, including the charge, color representation and spin, and obtaining a precise mass measurement. These signals provide well-motivated benchmark …
A natural, non-supersymmetric solution to the hierarchy problem generically requires fermionic partners of the top quark with masses not much heavier than 500 GeV. We study the pair production and detection at the LHC of the top partners with electric charge Q=5/3 (T_{5/3}) and Q=-1/3 (B), that are predicted in models where the Higgs is a pseudo-Goldstone boson. The exotic T_{5/3} fermion, in particular, is the distinct prediction of a LR custodial parity invariance of the electroweak symmetry breaking sector. Both kinds of new fermions decay to Wt, leading to a t\bar{t}WW final state. We focu…
We discuss complementarity of discovery reaches of heavier neutral Higgs bosons and charged Higgs bosons at the LHC and the International Linear Collider (ILC) in two Higgs doublet models (2HDMs). We perform a comprehensive analysis on their production and decay processes for all types of Yukawa interaction under the softly-broken discrete symmetry which is introduced to avoid flavour changing neutral currents, and we investigate parameter spaces of discovering additional Higgs bosons at the ILC beyond the LHC reach. We find that the 500 GeV run of the ILC with the integrated luminosity of 500…
The existence of magnetic monopoles, also predicted in some GUT theories, would symmetrise Maxwell equations and explain the charge quantisation. Searches for them are being performed in cosmic telescopes as well as in collider experiments, such as MoEDAL and ATLAS. In this report, we focus on the, least explored, photon-fusion mechanism, yet Drell-Yan results are discussed, too. Cross sections for monopoles of spin 0, 1/2 and 1 for an effective monopole-velocity-dependent magnetic charge are presented. For spin-1/2 and spin-1 monopoles, a magnetic-moment term is included, which is treated as …
We consider light top squarks (stops) in the minimal supersymmetric Standard Model at the Large Hadron Collider. Here, we assume that the lightest neutralino is the lightest supersymmetric particle (LSP) and the lighter stop is the next-to-LSP. Stop pair production is difficult to probe at the Large Hadron Collider for small stop-LSP mass splitting. It has been shown previously that even in this case stop detection is possible if one considers stop pair production in association with one hard jet. We reconsider this supersymmetric monojet signature and go beyond previous works by including the…
Supersymmetry with a compressed spectrum could be responsible for the negative results from supersymmetric searches at LHC. Squarks and gluinos well below the TeV scale could have escaped detection since all search channels lose sensitivity when the mass splitting between supersymmetric particles becomes small. Even in this stealthy situation, production of colored particles is probed in processes with supersymmetric particles produced in association with a high-pT photon. We show that searches for missing energy with a monophoton are a powerful tool, and that the 2011 LHC data already surpass…
The use of simplified models as a tool for interpreting dark matter collider searches has become increasingly prevalent, and while early Run II results are beginning to appear, we look to see what further information can be extracted from the Run I dataset. We consider three `standard' simplified models that couple quarks to fermionic singlet dark matter: an $s$-channel vector mediator with vector or axial-vector couplings, and a $t$-channel scalar mediator. Upper limits on the couplings are calculated and compared across three alternate channels, namely mono-jet, mono-$Z$ (leptonic) and mono-…
Considering the recently obtained value of $θ_{13}$ from Daya Bay and other reactor experiments we have studied the prospects of considering mono-energetic neutrino beam in studying $CP$ violation in the leptonic sector. Using a neutrino beam from electron capture process for nuclei $^{110}_{50}$Sn and $^{152}$Yb and considering two baselines - 130 Km and 250 Km with Water Cherenkov detector, we have shown the discovery reach of $CP$ violation in neutrino oscillation experiment. Particularly for $^{110}_{50}$Sn nuclei $CP$ violation could be found for about 80% of the possible $δ$ values for a…
In this review, we discuss recent developments in both the theory and the experimental searches of magnetic monopoles in past, current and future colliders and in the Cosmos. The theoretical models include, apart from the standard Grand Unified Theories, extensions of the Standard Model that admit magnetic monopole solutions with finite energy and masses that can be as light as a few TeV. Specifically, we discuss, among other scenarios, modified Cho-Maison monopoles and magnetic monopoles in (string-inspired, higher derivative) Born-Infeld extensions of the hypercharge sector of the Standard M…
Pair production of light top squarks at the 8-TeV LHC can be used to probe the gaugino-Higgsino sector of the Minimal Supersymmetric Standard Model. The case where the lightest neutralino is a mixture of Bino and Higgsino, satisfying the thermal dark matter relic density, is investigated. In such a scenario, the lightest top squark decays mostly into $(i)$ a top quark plus the second or third lightest neutralino, and $(ii)$ a bottom quark plus the lightest chargino, instead of a decay scenario of the lightest top squark into a top quark and the lightest neutralino. Final states with $\geq 2$ j…
Run 1 of the LHC has provided three new motivations for supersymmetry: the need to stabilize the electroweak vacuum, the mass of the Higgs boson, and the fact that its couplings are Standard Model-like (so far). The prospects for discovering (and measuring) supersymmetry during future runs of the LHC are discussed in the frameworks of the constrained MSSM (CMSSM), models with non-universal soft supersymmetry-breaking contributions to Higgs masses (NUHM1,2) and the phenomenological MSSM with 10 arbitrary soft supersymmetry-breaking parameters (pMSSM10). In addition to the classic searches for m…
We explore the implications of the mono-lepton plus missing transverse energy signature at the LHC, and point out its significance on understanding how dark matter interacts with quarks, where the signature arises from dark matter pair production together with a leptonically decaying W boson radiated from the initial state quarks. We derive limits using the existing W' searches at the LHC, and find an interesting interference between the contributions from dark matter couplings to up-type and down-type quarks. Mono-leptons can actually furnish the strongest current bound on dark matter interac…
We analyse the constraints on models of WIMP Dark Matter that can be derived from upper bounds on the "monojet" cross section at the LHC. These constraints were originally interpreted in the context of an effective field theory (EFT) where the Standard Model is extended by a dimension--6 operator whose coefficient is $1/Λ^2$. We show that combining the 8 TeV data of the ATLAS and CMS collaborations improves the bounds only slightly. We then analyze this final state in the context of simplified models with $s-$channel mediator. We show that if the decay width of the mediator is small, these sim…
We analyze the potential dark matter implications of LHC events with missing transverse momentum and a resonance, such as a Z', decaying to a pair of jets or leptons. This final state contains significant discovery potential, but has not yet been examined in detail by the LHC experiments. We introduce models of Z' production in association with dark matter particles, propose reconstruction and selection strategies, and estimate the sensitivity of the current LHC dataset.
We use ATLAS and CMS searches in the mono-jet + missing energy and mono-photon + missing energy final state to set limits on the couplings of dark matter to quarks and gluons. Working in an effective field theory framework we compare several existing mono-jet analyses and find that searches with high p_T cuts are more sensitive to dark matter. We constrain the suppression scale of the effective dark matter-Standard Model interactions, and convert these limits into bounds on the cross sections relevant to direct and indirect detection. We find that, for certain types of operators, in particular…
Searches for dark matter at colliders typically involve signatures with energetic initial-state radiation without visible recoil particles. Searches for mono-jet or mono-photon signatures have yielded powerful constraints on dark matter interactions with Standard Model particles. We extend this to the mono-Z signature and reinterpret an ATLAS analysis of events with a Z boson and missing transverse momentum to derive constraints on dark matter interaction mass scale and nucleon cross sections in the context of effective field theories describing dark matter which interacts via heavy mediator p…
The crucial search for the Higgs boson at future colliders is capable of discovering the Standard Model Higgs, but is not guaranteed to discover a Higgs that decays nonstandardly. Such new physics is motivated by many aspects; from experiment, by the tension between precision electroweak fits and the LEP2 direct search bound and from theory, by issues of satisfying the LEP2 bound in theories that naturally have a lighter Higgs. The consistent nonstandard Higgs scenario is that the Higgs is lighter than the LEP2 bound and is consistent with direct search limits because the dominant new decays a…
Current searches for dark matter at the LHC focus on mono-X signatures: the production of dark matter in association with a Standard Model (SM) particle. The simplest benchmark introduces a massive spin-1 mediator, the $Z^\prime$ boson, between the dark matter $χ$ and the SM. Limits derived from mono-X channels are most effective when the mediator can decay into two on-shell dark matter particles: $M_{Z'}\gtrsim 2M_χ$. We broaden the experimental reach into the complementary region, where the $Z^\prime$ mediator is much lighter than the dark matter. In this scenario the $Z^\prime$ mediates an …
The inert Two Higgs Doublet Model (i2HDM) is a theoretically well-motivated example of a minimal consistent Dark Matter(DM) model which provides mono-jet, mono-Z, mono-Higgs and Vector-Boson-Fusion+Missing Transverse Momentum signatures at the LHC, complemented by signals in direct and indirect DM search experiments. In this paper we have performed a detailed analysis of the constraints in the full 5D parameter space of the i2HDM, coming from perturbativity, unitarity, electroweak precision data, Higgs data from LHC, DM relic density, direct/indirect DM detection and LHC mono-jet analysis, as …
Mono-Z signal for dark matter searches at future lepton colliders and cosmological interpretation
Indian Institute of Technology Guwahati（印度理工学院古瓦哈提分校）；Indian Institute of Technology Hyderabad（印度理工学院海得拉巴分校）；Université Grenoble-Alpes（格勒诺布尔阿尔卑斯大学）；Indian Institute of Technology Kanpur（印度理工学院坎普尔分校）；Indian Institute of Science Education and Research Thiruvananthapuram（印度科学与教育研究所特里凡得琅分校）；University of the Witwatersrand（威特沃特斯兰德大学）；SGTB Khalsa College, University of Delhi（德里大学 SG TB 卡尔萨学院）
The prospects for discovering Higgs particles and studying their fundamental properties at future high--energy electron--positron and photon-photon colliders are reviewed. Both the Standard Model Higgs boson and the Higgs particles of its minimal supersymmetric extension are discussed. We also comment on a two Higgs doublet model searches at LEP 1. We update various results by taking into account the value of the top quark mass obtained by the CDF Collaboration and by including radiative corrections.
Monojet searches using Effective Field Theory (EFT) operators are usually interpreted as a robust and model independent constraint on direct detection (DD) scattering cross-sections. At the same time, a mediator particle must be present to produce the dark matter (DM) at the LHC. This mediator particle may be produced on shell, so that direct searches for the mediating particle can constrain the effective operator being applied to monojet constraints. In this first paper, we do a case study on t-channel models in monojet searches, where the (Standard Model singlet) DM is pair produced via a t-…
