Dark Matter Direct Detection Experiments Research Articles

SUSY dark matter in universal and nonuniversal gaugino mass models

We review the phenomenology of SUSY dark matter in various versions of MSSM, with universal and nonuniversal gaugino masses at the GUT scale. We start with the universal case (CMSSM), where the cosmologically compatible dark matter relic density is achieved only over some narrow regions of parameter space, involving some fine-tuning. Moreover, most of these regions are seriously challenged by the constraints from collider and direct dark matter detection experiments. Then we consider some simple and predictive nonuniversal gaugino mass models, based on SU(5) GUT. Several of these models offer viable SUSY dark matter candidates, which are compatible with the cosmic dark matter relic density and the above mentioned experimental constraints. They can be probed at the present and future collider and dark matter search experiments. Finally, we consider the nonuniversal gaugino mass model arising from anomaly mediated SUSY breaking. In this case the cosmologically compatible dark matter relic density requires dark matter mass of a few TeV, which puts it beyond the scope of collider and direct dark matter detection experiments. However, it has interesting predictions for some indirect dark matter detection experiments.

From direct detection to relic abundance: the case of proton-philic spin-dependent inelastic Dark Matter

We discuss strategies to make inferences on the thermal relic abundance of a Weakly Interacting Massive Particle (WIMP) when the same effective dimension-six operator that explains an experimental excess in direct detection is assumed to drive decoupling at freeze-out, and apply them to the explicit scenario of WIMP inelastic up-scattering with spin-dependent couplings to protons (proton-philic Spin-dependent Inelastic Dark Matter, pSIDM), a phenomenological set-up containing two Dark Matter (DM) particles χ1 and χ2 with masses mχ=mχ1 and mχ2=mχ+δ that we have shown in a previous paper to explain the DAMA effect in compliance with the constraints from other detectors. We also update experimental constraints on pSIDM, extend the analysis to the most general spin-dependent momentum-dependent interactions allowed by non-relativistic Effective Field Theory (EFT), and consider for the WIMP velocity distribution in our Galaxy f(v) both a halo-independent approach and a standard Maxwellian. Under these conditions we find that the DAMA effect can be explained in terms of the particle χ1 in compliance with all the other constraints for all the analyzed EFT couplings and also for a Maxwellian f(v). As far as the relic abundance is concerned, we show that the problem of calculating it by using direct detection data to fix the model parameters is affected by a strong sensitivity on f(v) and by the degeneracy between the WIMP local density ρχ and the WIMP-nucleon scattering cross section, since ρχ must be rescaled with respect to the observed DM density in the neighborhood of the Sun when the calculated relic density Ω is smaller than the observed one Ω0. As a consequence, a DM direct detection experiment is not directly sensitive to the physical cut-off scale of the EFT, but on some dimensional combination that does not depend on the actual value of Ω. However, such degeneracy can be used to develop a consistency test on the possibility that the WIMP is a thermal relic in the first place. When we apply it to the pSIDM scenario we find that only a WIMP with the standard spin-dependent interaction \U0001d4aa=χ̄1γμγ5χ2 q̄γμγ5 q + h.c. with quarks can be a thermal relic for, approximately, 10 GeV\\;≲ mχ≲ 16 GeV, 17 keV\\;≲ δ≲ 28 keV, and a large uncertainty on Ω, 6× 10−7Ω0≲ Ω ≲ Ω0. In order for the scenario to work the WIMP galactic velocity distribution must depart from a Maxwellian. Moreover, all the χ2 states must have already decayed today, and this requires some additional mechanism besides that provided by the \U0001d4aa operator.

Dark matter and exotic neutrino interactions in direct detection searches

We investigate the effect of new physics interacting with both Dark Matter (DM) and neutrinos at DM direct detection experiments. Working within a simplified model formalism, we consider vector and scalar mediators to determine the scattering of DM as well as the modified scattering of solar neutrinos off nuclei. Using existing data from LUX as well as the expected sensitivity of LUX-ZEPLIN and DARWIN, we set limit on the couplings of the mediators to quarks, neutrinos and DM. Given the current limits, we also assess the true DM discovery potential of direct detection experiments under the presence of exotic neutrino interactions. In the case of a vector mediator, we show that the DM discovery reach of future experiments is affected for DM masses mχ ≲ 10 GeV or DM scattering cross sections σχ ≲ 10−47 cm2. On the other hand, a scalar mediator will not affect the discovery reach appreciably.

Current status of direct dark matter detection experiments

Much like ordinary matter, dark matter might consist of elementary particles, and weakly interacting massive particles are one of the prime suspects. During the past decade, the sensitivity of experiments trying to directly detect them has improved by three to four orders of magnitude, but solid evidence for their existence is yet to come. We overview the recent progress in direct dark matter detection experiments and discuss future directions.

Dark matter and the Higgs in natural SUSY

Null results from dark matter (DM) direct detection experiments and the 125 GeV Higgs both pose serious challenges to minimal supersymmetry. In this paper, we propose a simple extension of the MSSM that economically solves both problems: a “dark sector” consisting of a singlet and a pair of SU(2) doublets. Loops of the dark sector fields help lift the Higgs mass to 125 GeV consistent with naturalness, while the lightest fermion in the dark sector can be viable thermal relic DM, provided that it is mostly singlet. The DM relic abundance is controlled by s-wave annihilation to tops and Higgsinos, leading to a tight relation between the relic abundance and the spin-dependent direct detection cross section. As a result, the model will be fully probed by the next generation of direct detection experiments. Finally we discuss the discovery potential at LHC Run II.

Spin-Dependent Weakly-Interacting-Massive-Particle-Nucleon Cross Section Limits from First Data of PandaX-II Experiment.

New constraints are presented on the spin-dependent weakly-interacting-massive-particle–- (WIMP-)nucleon interaction from the PandaX-II experiment, using a data set corresponding to a total exposure of 3.3×10^{4} kg day. Assuming a standard axial-vector spin-dependent WIMP interaction with ^{129}Xe and ^{131}Xe nuclei, the most stringent upper limits on WIMP-neutron cross sections for WIMPs with masses above 10 GeV/c^{2} are set in all dark matter direct detection experiments. The minimum upper limit of 4.1×10^{-41} cm^{2} at 90%confidence level is obtained for a WIMP mass of 40 GeV/c^{2}. This represents more than a factor of 2 improvement on the best available limits at this and higher masses. These improved cross-section limits provide more stringent constraints on the effective WIMP-proton and WIMP-neutron couplings.

Implications of heavy neutralino dark matter: The underlying structure in the hidden sector

The possibility of heavy neutralino dark matter (DM) in the gravity-mediation mechanism is explored. The appearance of the heavy lightest supersymmetric particle is seemingly suggested by Large Hadron Collider runs, which have not provided evidence of superparticles around the TeV region. On the basis of the so-called WIMPZILLA scenario, it is understood that the nonthermally produced DM has the larger mass than the reheating temperature. Hence, the expected DM mass should be more than 109 GeV so that thermal leptogenesis successfully occurs. In this paper, we first examine the generation of the Higgsino mass parameter [Formula: see text] in the context of gravity mediation, postulating that the resolution of the strong CP problem should be the criterion for arriving at a valid hypothesis for heavy neutralino DM. Accordingly, we address how the Peccei–Quinn (PQ) symmetry could influence dynamical supersymmetry breaking (DSB) models. It is found that as long as [Formula: see text] (the SUSY-breaking scale) approximately coincides with [Formula: see text] (the PQ-breaking scale), no DSB models can naturally account for the existence of the heavy neutralino DM, based upon the supersymmetric Dine–Fischler–Srednicki–Zhitinitski (DFSZ)-like mechanism. Thus, we attempt to construct a new model wherein hierarchical SUSY breakings occur. For this purpose, we propose gauge coupling unification in the hidden-sector dynamics at some high-energy scale, and we show that such a class of models can achieve [Formula: see text] through renormalization flow. As a consequence, the nonthermal neutralino, practically the wino-like one in our model, is shown to be a rather natural and viable DM candidate. Moreover, we argue that on the basis of Kac–Moody algebra, multiple breakdowns of supersymmetry may entail unified gauge dynamics. We also present a possible unified model. Finally, the heavy wino-like neutralino may be a DM candidate that will favor future direct DM detection experiments, mainly because its scattering on nuclei well conserves isospin symmetry.

Prospects for distinguishing dark matter models using annual modulation

It has recently been demonstrated that, in the event of a putative signal in dark matter direct detection experiments, properly identifying the underlying dark matter-nuclei interaction promises to be a challenging task. Given the most optimistic expectations for the number counts of recoil events in the forthcoming Generation 2 experiments, differentiating between interactions that produce distinct features in the recoil energy spectra will only be possible if a strong signal is observed simultaneously on a variety of complementary targets. However, there is a wide range of viable theories that give rise to virtually identical energy spectra, and may only differ by the dependence of the recoil rate on the dark matter velocity. In this work, we investigate how degeneracy between such competing models may be broken by analyzing the time dependence of nuclear recoils, i.e. the annual modulation of the rate. For this purpose, we simulate dark matter events for a variety of interactions and experiments, and perform a Bayesian model-selection analysis on all simulated data sets, evaluating the chance of correctly identifying the input model for a given experimental setup. We find that including information on the annual modulation of the rate may significantly enhance the ability of a single target to distinguish dark matter models with nearly degenerate recoil spectra, but only with exposures beyond the expectations of Generation 2 experiments.

Krypton and radon background in the PandaX-I dark matter experiment

We discuss an in-situ evaluation of the 85Kr, 222Rn, and 220Rn background in PandaX-I, a 120-kg liquid xenon dark matter direct detection experiment. Combining with a simulation, their contributions to the low energy electron-recoil background in the dark matter search region are obtained.

Reflectance dependence of polytetrafluoroethylene on thickness for xenon scintillation light

Many rare event searches including dark matter direct detection and neutrinoless double beta decay experiments take advantage of the high VUV reflective surfaces made from polytetrafluoroethylene (PTFE) reflector materials to achieve high light collection efficiency in their detectors. As the detectors have grown in size over the past decade, there has also been an increased need for ever thinner detector walls without significant loss in reflectance to reduce dead volumes around active noble liquids, outgassing, and potential backgrounds. We report on the experimental results to measure the dependence of the reflectance on thickness of two PTFE samples at wavelengths near 178nm. No change in reflectance was observed as the wall thickness of a cylindrically shaped PTFE vessel immersed in liquid xenon was varied between 1mm to 9.5mm.

Search for dark matter with the ATLAS detector at the LHC

An overview of recent searches for dark matter production in association with visible particles with the ATLAS detector at LHC is presented. Interpretations of the results of the searches in terms of the effective field theory and simplified models is discussed. The exclusion limits placed by the ATLAS searches are compared to the constraints from direct dark matter detection experiments.

New LUX result constrains exotic quark mediators with the vector dark matter

The scenario of the compressed mass spectrum between heavy quark and dark matter is a challenge for LHC searches. However, the elastic scattering cross-section between dark matter and nuclei in dark matter direct detection experiments can be enhanced with nearly degenerate masses between heavy quarks and dark matter. In this paper, we illustrate such scenario with a vector dark matter, using the latest result from LUX 2016. The mass constraints on heavy quarks can be more stringent than current limits from LHC, unless the coupling strength is very small. However, the compress mass spectrum with allowed tiny coupling strength makes the decay lifetime of heavy quarks longer than the timescale of QCD hadronization.

Reconstructing the three-dimensional local dark matter velocity distribution

Directionally sensitive dark matter (DM) direct detection experiments present the only way to observe the full three-dimensional velocity distribution of the Milky Way halo local to Earth. In this work we compare methods for extracting information about the local DM velocity distribution from a set of recoil directions and energies in a range of hypothetical directional and non-directional experiments. We compare a model independent empirical parameterisation of the velocity distribution based on an angular discretisation with a model dependent approach which assumes knowledge of the functional form of the distribution. The methods are tested under three distinct halo models which cover a range of possible phase space structures for the local velocity distribution: a smooth Maxwellian halo, a tidal stream and a debris flow. In each case we use simulated directional data to attempt to reconstruct the shape and parameters describing each model as well as the DM particle properties. We find that the empirical parametrisation is able to make accurate unbiased reconstructions of the DM mass and cross section as well as capture features in the underlying velocity distribution in certain directions without any assumptions about its true functional form. We also find that by extracting directionally averaged velocity parameters with this method one can discriminate between halo models with different classes of substructure.

CP violating scalar Dark Matter

We study an extension of the Standard Model (SM) in which two copies of the SM scalar $SU(2)$ doublet which do not acquire a Vacuum Expectation Value (VEV), and hence are \textit{inert}, are added to the scalar sector. We allow for CP-violation in the \textit{inert} sector, where the lightest \textit{inert} state is protected from decaying to SM particles through the conservation of a $Z_2$ symmetry. The lightest neutral particle from the \textit{inert} sector, which has a mixed CP-charge due to CP-violation, is hence a Dark Matter (DM) candidate. We discuss the new regions of DM relic density opened up by CP-violation, and compare our results to the CP-conserving limit and the Inert Doublet Model (IDM). We constrain the parameter space of the CP-violating model using recent results from the Large Hadron Collider (LHC) and DM direct and indirect detection experiments.

Study of WIMP annihilations into a pair of on-shell scalar mediators

In this article, we focus on new scalar $\ensuremath{\phi}$ mediated scalar/vectorial weakly interacting massive particles (WIMPs) with $\ensuremath{\phi}$'s mass slightly below the WIMP mass. To explain the Galactic center 1--3 GeV gamma-ray excess, here we consider the case that a WIMP pair predominantly annihilates into an on-shell $\ensuremath{\phi}\ensuremath{\phi}$ pair with $\ensuremath{\phi}$ mainly decaying to $\ensuremath{\tau}\overline{\ensuremath{\tau}}$. The masses of WIMPs are in a range about 14--22 GeV, and the annihilations of WIMPs are phase space suppressed today. In this annihilation scheme, the couplings of the $\ensuremath{\phi}$-standard model (SM) particles are almost arbitrarily small, and the WIMP-nucleus spin-independent scattering can be tolerant by the present dark matter (DM) direct detections. A scalar mediator-Higgs field mixing is introduced, which is small and available. The lower limit on the couplings of the $\ensuremath{\phi}$-SM particles set by the thermal equilibrium in the early Universe is derived, and this constraint is above the neutrino background for scalar DM in direct detections. The WIMPs may be detectable at the upgraded DM direct detection experiment in the next few years, and the exotic decay $h\ensuremath{\rightarrow}\ensuremath{\phi}\ensuremath{\phi}$, the production of $\ensuremath{\phi}$ may be observable at the future high-luminosity ${e}^{+}{e}^{\ensuremath{-}}$ collider.

Alignment without decoupling: The portal to light dark matter in the MSSM

We study light, thermal neutralino dark matter in the sub-GeV to $\ensuremath{\sim}65\text{ }\text{ }\mathrm{GeV}$ mass range in the minimal supersymmetric extension of the Standard Model. We consider realizations of the limit of alignment without decoupling in the Higgs sector where the heavier $CP$-even Higgs impersonates the observed Higgs state at 125 GeV, while the lighter $CP$-even Higgs is the mediator of dark matter annihilation. We single out three distinct and novel possibilities for light dark matter: (i) a neutralino with mass around half the light Higgs mass, in the sub-GeV to $\ensuremath{\sim}30\text{ }\text{ }\mathrm{GeV}$ mass range; (ii) a neutralino with a mass around half the pseudoscalar Higgs boson mass, in our examples around $(60--65)\text{ }\text{ }\mathrm{GeV}$; (iii) a very light neutralino with mass around the light Higgs mass, pair annihilating to Higgs pairs. We discuss the implications of all these possibilities for indirect and direct dark matter detection experiments, and we demonstrate that all scenarios will be tested by next generation direct detection experiments. We also emphasize that the unique Higgs phenomenology of this setup warrants a dedicated search program at the LHC.

WIMP dark matter in a well-tempered regime — A case study on singlet-doublets fermionic WIMP

Serious searches for the weakly interacting massive particle (WIMP) have now begun. In this context, the most important questions that need to be addressed are: "To what extent can we constrain the WIMP models in the future?" and "What will then be the remaining unexplored regions in the WIMP parameter space for each of these models?" In our quest to answer these questions, we classify WIMP in terms of quantum number and study each case adopting minimality as a guiding principle. As a first step, we study one of the simple cases of the minimal composition in the well-tempered fermionic WIMP regime, namely the singlet-doublets WIMP model. We consider all available constraints from direct and indirect searches and also the predicted constraints coming from the near future and the future experiments. We thus obtain the current status, the near future prospects and the future prospects of this model in all its generality. We find that in the future, this model will be constrained almost solely by the future direct dark matter detection experiments (as compared to the weaker indirect and collider constraints) and the cosmological (relic density) constraints and will hence be gradually pushed to the corner of the coannihilation region, if no WIMP signal is detected. Future lepton colliders will then be useful in exploring this region not constrained by any other experiments.

Measurement of the ionization produced by sub-keV silicon nuclear recoils in a CCD dark matter detector

We report a measurement of the ionization efficiency of silicon nuclei recoiling with sub-keV kinetic energy in the bulk silicon of a charge-coupled device (CCD). Nuclear recoils are produced by low-energy neutrons ($<$24 keV) from a $^{124}$Sb-$^{9}$Be photoneutron source, and their ionization signal is measured down to 60 eV electron equivalent. This energy range, previously unexplored, is relevant for the detection of low-mass dark matter particles. The measured efficiency is found to deviate from the extrapolation to low energies of the Lindhard model. This measurement also demonstrates the sensitivity to nuclear recoils of CCDs employed by DAMIC, a dark matter direct detection experiment located in the SNOLAB underground laboratory.

Studying generalised dark matter interactions with extended halo-independent methods

The interpretation of dark matter direct detection experiments is complicated by the fact that neither the astrophysical distribution of dark matter nor the properties of its particle physics interactions with nuclei are known in detail. To address both of these issues in a very general way we develop a new framework that combines the full formalism of non-relativistic effective interactions with state-of-the-art halo-independent methods. This approach makes it possible to analyse direct detection experiments for arbitrary dark matter interactions and quantify the goodness-of-fit independent of astrophysical uncertainties. We employ this method in order to demonstrate that the degeneracy between astrophysical uncertainties and particle physics unknowns is not complete. Certain models can be distinguished in a halo-independent way using a single ton-scale experiment based on liquid xenon, while other models are indistinguishable with a single experiment but can be separated using combined information from several target elements.

Searching for singlino-Higgsino dark matter in the NMSSM

We study a simplified scenario in the next-to-minimal supersymmetric standard model with a split electroweak spectrum, in which only the singlino and higgsinos are light and other superpartners are decoupled. Serving as a dark matter candidate, a singlino-dominated neutralino $\tilde{\chi}_1^0$ should have either resonant annihilation effects or sizable higgsino components to satisfy the observed relic abundance. The sensitivities of LHC searches and dark matter detection experiments are investigated. With an integrated luminosity of $30 (300) \mathrm{fb}^{-1}$, $3l + E_\mathrm{T} \!\!\!\!\!\!\!/ \;\;\;$and $2l + E_\mathrm{T} \!\!\!\!\!\!\!/ \;\;\;$ searches at the 13 (14) TeV LHC are expected to reach up to $m_{\tilde{\chi}_1^0}\sim 150 (230) \mathrm{GeV}$ and $m_{\tilde{\chi}_2^0,\tilde{\chi}_1^{\pm}}\sim 320 (480) \mathrm{GeV}$. Near future dark matter direct and indirect detection experiments can cover some parameter regions where collider searches lose their sensitivities.