The signatures of dark matter at the LHC commonly involve, in simplified scenarios, the production of a single particle plus large missing energy, from the undetected dark matter. However, in $Z'$-portal scenarios anomaly cancellation requires the presence of extra dark leptons in the dark sector. We investigate the signatures of the minimal scenarios of this kind, which involve cascade decays of the extra $Z'$ boson into the dark leptons, identifying a four-lepton signal as the most promising one. We estimate the sensitivity to this signal at the LHC, the high-luminosity LHC upgrade, a possible high-energy upgrade, as well as a future circular collider. For $Z'$ couplings compatible with current dijet constraints the multilepton signals can reach the $5σ$ level already at Run 2 of the LHC. At future colliders, couplings two orders of magnitude smaller than the electroweak coupling can be probed with $5σ$ sensitivity.
The U(1)_D gauge sector containing one dark Higgs boson h_D and one dark photon γ_D may be explored through the decays of the 126 GeV particle discovered at the Large Hadron Collider (LHC), assumed here as the heavier mass eigenstate h_1 in the mixing of the standard model h with h_D. The various decays of h_1 to γ_D γ_D, h_2 h_2, h_2 γ_D γ_D and h_2 h_2 h_2 would yield multilepton final states through the mixing of γ_D with the photon and the decay h_2 \to γ_D γ_D, where h_2 is the lighter dark Higgs. Future searches for signals of multilepton jets at the LHC may reveal the existence of this …
The PADME experiment is searching for the Dark Photon $A'$ in the $e^{+}e^{-} \to γA'$ process, assuming a $A'$ decay into invisible particles. In extended Dark Sector models, a Dark Higgs $h'$ can be produced alongside $A'$ in the process $e^{+}e^{-} \to h' A'$. If the $h'$ mass is greater than twice the $A'$ mass the final state will be composed by three $e^{+}e^{-}$ pairs. Such extremely rare process is explorable by the PADME experiment, which could get a first measure and impose limits on models of physics beyond the Standard Model.
We perform a comprehensive dark matter analysis of left-right supersymmetric scenarios that includes constraints from dark matter direct and indirect detection experiments and that presents distinctive features from those available in minimal supersymmetry. We concentrate on dark matter candidates which, while satisfying all constraints, are different from those of the minimal supersymmetric standard model. We consider in our analysis all possible co-annihilation channels relevant for setups in which several states are light and nearly degenerate, and devise a set of representative benchmark p…
We revisit the scalar singlet dark matter (DM) scenario with a pair of dark lepton partners which form a vectorlike Dirac fermionic doublet. The extra doublet couples with the Standard Model (SM) leptonic doublet and the scalar singlet via a non-SM-like Yukawa structure. As a result, (i) since the extra fermionic states interact with other dark sector particles as well as the SM via gauge and Yukawa interactions, it gives rise to new DM annihilation processes including pair annihilation as well as coannihilation channels, and (ii) such a Yukawa structure opens up new production channels for le…
Weakly-coupled models for the 750 GeV diphoton resonance often invoke new particles carrying both color and/or electric charges to mediate loop-induced couplings of the resonance to two gluons and two photons. The new colored particles may not be stable and could decay into final states containing standard model particles. We consider an electroweak doublet of vector-like quarks (VLQs) carrying electric charges of 5/3 and 2/3, respectively, which mediate the loop-induced couplings of the 750 GeV resonance. If the VLQ has a mass at around 1 TeV, it naturally gives rise to the observed diphoton …
Leptonic signatures of Dark Matter (DM) are one of the cleanest ways to discover such a secluded form of matter at high energy colliders. We explore the full parameter space relevant to multi-lepton (2- and 3-lepton) signatures at the Large Hadron Collider (LHC) from representative minimal consistent models with scalar and fermion DM. In our analysis, we suggest a new parametrisation of the model parameter spaces in terms of the DM mass and mass differences between DM and its multiplet partners. This parametrisation allows us to explore properties of DM models in their whole parameter space. T…
A possible feature of the inert doublet model (IDM) is to provide a dark matter candidate together with an alteration of both direct and indirect collider constraints that allow for a heavy Higgs boson. We study the IDM in light of recent results from Higgs searches at the Large Hadron Collider (LHC) in combination with dark matter direct detection limits from the XENON experiment. We ask under what conditions the IDM can still accommodate a heavy Higgs boson. We find that IDM scenarios with a Higgs boson in the mass range 160-600 GeV are ruled out only when all experimental constraints are co…
As sequel to a recent paper we examine the phenomenology of the full electroweakino sector of the pMSSM without invoking the adhoc but often employed assumption that the heavier ones are decoupled. We identify several generic models which illustrate the importance of the heavier electroweakinos and constrain them with the LHC $3l$ + ${E\!\!\!\!/_T}$ data. The constraints are usually stronger than that for decoupled heavier electroweakinos indicating that the LHC data is already sensitive to their presence. We also take into account the constraints from the observed dark matter relic density of…
We study in detail the collider signatures of an $SU(2)_R$ fermionic quintuplet in the framework of left-right symmetric model in the context of the 13 TeV LHC. Apart from giving a viable dark matter candidate ($χ^0$), this model provides unique collider imprints in the form of same-sign multileptons through the decays of multi-charged components of the quintuplet. In particular, we consider the scenario where the quintuplet carries $(B - L) = 4$ charge, allowing for the presence of high charge-multiplicity particles with relatively larger mass differences among them compared to $(B - L)$ = 0 …
We consider a fermionic dark matter (DM) in the left-right symmetric framework by introducing a pair of vector-like (VL) doublets in the particle spectrum. The stability of the DM is ensured through an unbroken $\mathcal{Z}_2$ symmetry. We explore the parameter space of the model compatible with the observed relic density and direct and indirect detection cross sections. The presence of charged dark fermions opens up an interesting possibility for the doubly charged Higgs signal at LHC and ILC. The signal for the doubly charged scalar decaying into the dark sector is analyzed in multilepton fi…
The aim of this paper is to showcase the novel multilepton ($nl + E\!\!\!\!/_T$, n = 3 - 5) signals, hitherto unexplored at the LHC, arising from the heavier electroweakinos, in several generic pMSSMs at the upcoming LHC experiments. We first briefly review our old constraints on the full electroweakino sector of these models, containing both lighter and heavier sparticles, using the ATLAS trilepton data from the LHC Run I. Next we derive new stronger constraints on this sector for the first time using the ATLAS Run II data. We identify some benchmark points and explore the prospect of observi…
Extremely weakly interacting particles like the gravitino may be stable enough on cosmological time scales to constitute a good dark matter candidate even in the presence of R-parity violation. We consider the possibility that the recently identified 3.5 keV x-ray line can be generated in light gravitino decays to neutrinos and photons. We find that this is indeed possible in loop processes induced by trilinear lepton-number-violating couplings. We show that in order to avoid overproduction of gravitinos, the reheating temperature has to be at most around 100 GeV to 1 TeV. Finally we briefly d…
We revisit the multilepton ($ml$) + ${E\!\!\!\!/_T}$ + $X$ signatures of the Inert Doublet Model (IDM) of dark matter in future LHC experiments for $m =$ 3, 4 and simulate, for the first time, the $m = 5$ case. Here $X$ stands for any number of jets. We illustrate these signals with benchmark points consistent with the usual constraints like unitarity, perturbativity, the precision electroweak data, the observed dark matter relic density of the Universe and, most importantly, the stringent LHC constraints from the post Higgs ($h$) discovery era like the measured $M_h$ and the upper bound on th…
We study the signatures of the triplet-quadruplet dark matter model at the LHC and future colliders, including the 100 TeV Super Proton-Proton Collider and the 240 GeV Circular Electron Positron Collider. The dark sector in this model contains one fermionic electroweak triplet and two fermionic quadruplets, which have two kinds of Yukawa couplings to the Higgs doublet. Electroweak production signals of the dark sector fermions in the $\text{monojet}+/\!\!\!\!E_\mathrm{T}$, disappearing track, and $\text{multilepton}+/\!\!\!\!E_\mathrm{T}$ channels at the LHC and the Super Proton-Proton Collide…
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 …
We perform a multilepton channel analysis in the context of the Large Hadron Collider (LHC) for Wilkinson Microwave Anisotropy Probe (WMAP) compatible points in a model with non-universal scalar masses, which admits a Higgs funnel region of supersymmetry dark matter even for a small $\tanβ$. In addition to two and three-lepton final states, four-lepton events, too, are shown to be useful for this purpose. We also compare the collider signatures in similar channels for WMAP compatible points in the minimal supergravity (mSUGRA) framework with similar gluino masses. Some definite features of suc…
Vector boson dark matter (DM) appears in $SU(2)_N$ extension ($N$ stands for neutral) of Standard Model (SM) where an additional global $U(1)_P$ symmetry is assumed and results in a generalized lepton number defined as: $L=P+T_{3N}$. Breaking of $U(1)_P$ leads to the breaking of $L$ to $(-1)^L$, thus stabilizing DM through modified $R=(-1)^{3B+L+2J}$. This model, already discussed in literature, offers several novel features to elaborate upon. For example, $t$-channel annihilation and dominant $s$-channel direct search, along with co-annihilation, helps the DM to evade stringent direct search …
We study the phenomenology of a hypercharge-zero SU(2) triplet scalar whose existence is motivated by two-step electroweak symmetry-breaking. We consider both the possibility that the triplets are stable and contribute to the dark matter density, or that they decay via mixing with the standard model Higgs boson. The former is constrained by disappearing charged track searches at the LHC and by dark matter direct detection experiments, while the latter is constrained by existing multilepton collider searches. We find that a two-step electroweak phase transition involving a stable triplet with a…
We study the collider phenomenology of dark matter pair production at the LHC in simplified dark matter models and in the MSSM. Among the large space of dark matter models, we focus on two particular models where a fermionic dark matter candidate interacts with the Standard Model via the exchange of either a vector mediator in the s-channel or coloured scalar mediators in the t-channel. We find that the simplified models are capable of reproducing the predictions of the MSSM to some extent in simplified supersymmetric scenarios, but lack the complexity to descibe the complete theory over the f…
Dark matter is one of the main puzzles in fundamental physics and the goal of a diverse, multi-pronged research program. Underground and astrophysical searches search for dark matter particles in the cosmos, either by interacting directly or by searching for dark matter annihilation. Particle colliders, in contrast, might produce dark matter in the laboratory and are able to probe all basic interactions. They are sensitive to low dark matter masses, provide complementary information at higher masses and are subject to different systematic uncertainties. Collider searches are therefore an impor…
In the extensive efforts to understand the nature of Dark Matter and searches at colliders, the LHCb experiment has a unique sensitivity to low mass Dark Matter candidates. These proceedings present recent results and prospects on Dark Matter searches with the LHCb experiment that achieve world-leading sensitivities.
Martin has proposed a scenario dubbed ``compressed supersymmetry'' (SUSY) where the MSSM is the effective field theory between energy scales M_{\rm weak} and M_{\rm GUT}, but with the GUT scale SU(3) gaugino mass M_3<< M_1 or M_2. As a result, squark and gluino masses are suppressed relative to slepton, chargino and neutralino masses, leading to a compressed sparticle mass spectrum, and where the dark matter relic density in the early universe may be dominantly governed by neutralino annihilation into ttbar pairs via exchange of a light top squark. We explore the dark matter and collider signa…
In single-component theories of dark matter, the $2\to 2$ amplitudes for dark-matter production, annihilation, and scattering can be related to each other through various crossing symmetries. These crossing relations lie at the heart of the celebrated complementarity which underpins different existing dark-matter search techniques and strategies. In multi-component theories of dark matter, by contrast, there can be many different dark-matter components with differing masses. This then opens up a new, "diagonal" direction for dark-matter complementarity: the possibility of dark-matter decay fro…
We consider a $U(1)'$ supersymmetric seesaw model in which a right-handed sneutrino is a thermal dark matter candidate whose relic density can be in the right range due to its coupling to relatively light $\tilde{Z'}$, the superpartner of the extra gauge boson $Z'$. Such light $\tilde Z'$ can be produced at the LHC through cascade decays of colored superparticles, in particular, stops and sbottoms, and then decay to a right-handed neutrino and a sneutrino dark matter, which leads to lepton flavor violating signals of same/opposite-sign dileptons (or multileptons) accompanied by large missing e…
In the simple Higgs-portal dark matter model with a conserved dark matter number, we show that there exists a non-topological soliton state of dark matter. This state has smaller energy per dark matter number than a free particle state and has its interior in the electroweak symmetric vacuum. It could be produced in the early universe from first-order electroweak phase transition and contribute most of dark matter. This electroweak symmetric dark matter ball is a novel macroscopic dark matter candidate with an energy density of the electroweak scale and a mass of 1 gram or above. Because of it…
Superheavy dark matter may show its presence in high energy neutrino signals detected on earth. From the latest results of IceCube, we could set the strongest lower bound on the lifetime of dark matter beyond 100 TeV around $10^{28} {\rm sec}$. The excess around a PeV is noticed and may be interpreted as the first signal of DM even though further confirmation and dedicated searches are invited.
I review prospects for detecting dark matter in space-based experiments, with an emphasis on recent developments. I propose the ``Martha Stewart criterion'' for identifying dark matter candidates that are particularly worth investigation and focus on three that satisfy it: neutralino dark matter, Kaluza-Klein dark matter, and superWIMP gravitino dark matter.
The simplest renormalizable effective field theories with asymmetric dark matter bound states contain two additional gauge singlet fields one being the dark matter and the other a mediator particle that the dark matter annihilates into. We examine the physics of one such model with a Dirac fermion as the dark matter and a real scalar mediator. For a range of parameters the Yukawa coupling of the dark matter to the mediator gives rise to stable asymmetric dark matter bound states. We derive properties of the bound states including nuggets formed from $N\gg1$ dark matter particles. We also consi…
We show that current and imminent underground detectors are capable of precision astrometry of dark matter. First we show that galactic dark matter velocity distributions can be obtained from reconstructed tracks of dark matter scattering on multiple nuclei during transit; using the liquid scintillator neutrino detector SNO+ as an example, we find that the dark matter velocity vector can be reconstructed event-by-event with such a small uncertainty, that the precision of dark matter astrometry will be limited mainly by statistics. We then determine the number of dark matter events required to …
Velocity distribution of dark matter is assumed to be isotropic in most cases, however, anisotropy is suggested in some simulations. Directional direct detection of dark matter is a hopeful way to discriminate the anisotropy of dark matter velocity distribution. We simulate the dark matter and target scattering in the directional direct detection, and investigate conditions required to discriminate the anisotropy. If dark matter mass is known, $O(10^3)-O(10^4)$ events are required for the discrimination if the dark matter mass is known by other experiments. We also study the case that the dark…
We study a class of simplified dark matter models in which one dark matter particle couples with a mediator and a Standard Model fermion. In such models, collider and direct detection searches probe complimentary regions of parameter space. For Majorana dark matter, direct detection covers the region near mediator-dark matter degeneracy, while colliders probe regions with a large dark matter and mediator mass splitting. For Dirac and complex dark matter, direct detection is effective for the entire region above the mass threshold, but colliders provide a strong bound for dark matter lighter th…
The rate of dark matter-electron scattering depends on the underlying velocity distribution of the dark matter halo. Importantly, dark matter-electron scattering is particularly sensitive to the high-velocity tail, which differs significantly amongst the various dark matter halo models. In this work, we summarize the leading halo models and discuss the various parameters which enter them. We recommend updated values for these parameters based on recent studies and measurements. Furthermore, we quantify the dependence of the dark matter-electron scattering rate on the choice of halo model and p…
Annihilation radiation from neutralino dark matter at the Galactic center (GC) would be greatly enhanced if the dark matter were strongly clustered around the supermassive black hole (SBH). The existence of a dark-matter "spike" is made plausible by the observed, steeply-rising stellar density near the GC SBH. Here the time-dependent equations describing gravitational interaction of the dark matter particles with the stars are solved. Scattering of dark matter particles by stars would substantially lower the dark matter density near the GC SBH over 10^10 yr, due both to kinetic heating, and to…
Since neither supersymmetry nor dark matter WIMPs have yet been observed, pessimism about their reality has been growing. Here we discuss a new supersymmetric theory and a new dark matter candidate which are naturally consistent with current experimental results, but which imply a plethora of new phenomena awaiting discovery within the foreseeable future.
We present a simple extension of the standard model that gives rise to baryogenesis a has a dark matter candidate of O(GeV) mass. A minimal set of new fields required for baryogenesis includes two O(TeV) colored scalars and a singlet fermion. The fermion also becomes a viable dark matter candidate when its is nearly degenerate in mass with the proton. Dark matter and baryon asymmetry are produced form the decay of heavy scalars, which can lead to a natural explanation of the baryon-dark matter coincidence problem. The dark matter candidate escapes direct and indirect detection, but can be prob…
We propose a unified scenario to generate the masses of Dirac neutrinos and cold dark matter at the TeV scale, understand the origin of dark energy and explain the matter-antimatter asymmetry of the universe. This model can lead to significant impact on the Higgs searches at LHC.
We introduce an $SU(2)_X^{}$ dark sector without any fermions and then realize a non-abelian kinetic mixing between the dark $SU(2)_X^{}$ gauge fields and the standard model $SU(2)_L^{}\times U(1)_Y^{}$ gauge fields. While one of the dark gauge bosons becomes a dark photon, the others can keep stable to form a dark matter particle. The nearly degenerate masses of dark photon and dark matter could be tested if the dark photon and the dark matter are both observed in the future.
A brief overview of our current understanding of abundance and properties of dark energy and dark matter is presented. A more focused discussion of supersymmetric dark matter follows. Included is a frequentist approach to the supersymmetric parameter space and consequences for the direct detection of dark matter.
A simple model of the Majorana neutrino with the see-saw mechanism is studied, assuming that two light neutrinos are the hot dark matters with equal mass of 2.4 eV in the cold plus hot dark matter model of cosmology. We find that the heavy neutrino, which is the see-saw partner with the remaining one light neutrino, can be the cold dark matter, if the light neutrino is exactly massless. This cold dark matter neutrino is allowed to have the mass of the wide range from 5.9 x 10^2 eV to 2.2 x 10^7 eV.
We attempt to answer whether neutrinos and antineutrinos, such as those in the cosmic neutrino background, would clusterize among themselves or even with other dark-matter particles, under certain time span, say 1 Gyr. With neutrino masses in place, the similarity with the ordinary matter increases and so is our confidence for neutrino clustering if time is long enough. In particular, the clusterings could happen with some seeds (cf. see the text for definition), the chance in the dark-matter world to form dark-matter galaxies increases. If the dark-matter galaxies would exist in a time span o…
Even though the sensitivity of direct dark matter search experiments reach the level about $10^{-45}~{\rm cm}^2$, there is no confident signal of dark matter been observed. We point out that, if dark matter is a vector boson, the null result in direct dark matter search experiments may due to the destructive effects in dark-matter-nucleon elastic scattering. We illustrate the scenario using a modified Higgs portal model that includes exotic quarks. The significant cancellation can occur for certain mass gap between heavy quark and dark matter. As a result, the spin-independent dark-matter-nucl…
We analyze the annihilation cross section of dark matter which interacts with the standard model sector over the scalar unparticle propagator. We observe that the annihilation cross section of dark matter pair is sensitive to the dark matter mass and the scaling dimension of scalar unparticle. We estimate a range for the dark matter mass and the scaling dimension of scalar unparticle by using the current dark matter abundance.
What is the upper limit of the mass of the neutralino dark matter whose thermal relic is consistent with the observation? If the neutralino dark matter and colored sparticles are extremely degenerated in mass, with a mass difference less than the QCD scale, the dark matter annihilation is significantly increased and enjoys the "second freeze-out" after the QCD phase transition. In this case, the neutralino dark matter with a mass much greater than 100 TeV can realize the correct dark matter abundance. We study the dark matter abundance and its detection in the case of such highly degenerated m…
We construct an explicit, TeV-scale model of decaying dark matter in which the approximate stability of the dark matter candidate is a consequence of a global symmetry that is broken only by instanton-induced operators generated by a non-Abelian dark gauge group. The dominant dark matter decay channels are to standard model leptons. Annihilation of the dark matter to standard model states occurs primarily through the Higgs portal. We show that the mass and lifetime of the dark matter candidate in this model can be chosen to be consistent with the values favored by fits to data from the PAMELA …
Non-relativistic dark matter scattering with nucleons is constrained by direct detection experiments. We use the XENON constraints on the spin-independent and spin-dependent cross section for dark matter scattering with nucleons to constrain a hypothetical Majorana fermionic dark matter particle's couplings to the Higgs boson and Z boson. In the procedure we illustrate the change in the dark matter nucleon cross section as one goes from non-relativistic, coherent scattering to relativistic, incoherent scattering. While the Z invisible decay width excludes directly couplings of dark matter to o…
We attempt to understand the baryon-dark-matter coincidence problem within the quark seesaw extension of the standard model where parity invariance is used to solve the strong CP problem. The $SU(2)_L\times SU(2)_R\times U(1)_{B-L}$ gauge symmetry of this model is extended by a dark $U(1)_X$ group plus inclusion of a heavy neutral vector-like fermion $χ_{L,R}$ charged under the dark group which plays the role of dark matter. All fermions are Dirac type in this model. Decay of heavy scalars charged under $U(1)_X$ leads to simultaneous asymmetry generation of the dark matter and baryons after sp…
Dark matter can be produced in the early universe via the freeze-in or freeze-out mechanisms. Both scenarios were investigated in references, but the production of dark matters via the combination of these two mechanisms are not addressed. In this paper we propose a hybrid dark matter model where dark matters have two components with one component produced thermally and the other one produced non-thermally. We present for the first time the analytical calculation for the relic abundance of the Higgs portal hybrid dark matter, then we investigate constraints on the parameter space of the model …
We consider inelastic dark matter scenarios with dark photon mediator and a dark Higgs boson. The dark Higgs boson spontaneously breaks the gauge symmetry associated with the dark photon, and gives the mass to the dark photon and the mass difference to dark particles. Such a dark Higgs boson can decay into the dark particles and hence can be another source of the dark particles at collider experiments. We analyze the sensitivity to decays of the excited state into the dark matter and charged particles at the FASER 2 experiment in fermion and scalar inelastic dark matter scenarios. We consider …
What if the dark matter-nucleon scattering cross section is too small to be detected by direct detection experiments? It is well known in the literature that some interactions lead to dark matter-nucleon scattering cross sections that can be velocity and momentum suppressed. We show that in the case of bosonic dark matter, neutron star spectroscopy offers a possible detection. Firstly, we discuss the case of scalar dark matter with scalar, pseudoscalar, and vector mediators. Later, we do this exercise for vector dark matter. We show that, depending on the nature of dark matter and the interact…
