We consider models of light super-weakly interacting cold dark matter, with O(10-100) keV mass, focusing on bosonic candidates such as pseudoscalars and vectors. We analyze the cosmological abundance, the gamma-background created by particle decays, the impact on stellar processes due to cooling, and the direct detection capabilities in order to identify classes of models that pass all the constraints. In certain models, variants of photoelectric (or axioelectric) absorption of dark matter in direct-detection experiments can provide a sensitivity to the superweak couplings to the Standard Model which is superior to all existing indirect constraints. In all models studied, the annual modulation of the direct-detection signal is at the currently unobservable level of O(10^{-5}).
We consider possible mechanisms via which electroweak scale WIMPs χ^0 could provide the source of the INTEGRAL/SPI 511 keV photon flux from the galactic centre. We consider scenarios where the WIMP spectrum contains near-degeneracies, with MeV-scale splitting, and focus on three possible production mechanisms for galactic positrons: (i) collisional excitation of the WIMP to a nearby charged state, χ^0 + χ^0 -> χ^+ + χ^-, with the subsequent decay producing positrons; (ii) capture of the WIMP by nuclei in the galactic interstellar medium, χ^0 + N -> e^+ + (χ^- N); and (iii) the decay of a nearb…
The origin of both the diffuse high-latitude MeV gamma-ray emission and the 511 keV line flux from the Galactic bulge are uncertain. Previous studies have invoked dark matter physics to independently explain these observations, though as yet none has been able to explain both of these emissions within the well-motivated framework of Weakly-Interacting Massive Particles (WIMPs). Here we use an unstable WIMP dark matter model to show that it is in fact possible to simultaneously reconcile both of these observations, and in the process show a remarkable coincidence: decaying dark matter with MeV …
The unidentified emission line at the energy of $\sim$3.5~keV observed in X-rays from galaxy clusters may originate from a process involving a dark matter particle. On the other hand, a weakly interacting massive particle (WIMP) has been an attractive dark matter candidate, due to its well-understood thermal production mechanism and its connection to physics at the TeV scale. In this paper, we pursue the possibility that the 3.5-keV X-ray arises from a late time decay of a WIMP dark matter into another WIMP dark matter, both of which have the mass of $O(100)$~GeV and whose mass splitting is ab…
Bosonic super-WIMPs, including pseudoscalar and vector particles, are dark matter candidates. Until now, many underground experiments searches for super-WIMPs have been performed in the mass range of a few $\rm keV/c^2$ to 1 $\rm MeV/c^2$. All these searches utilize the absorption process of a super-WIMP by a target atom in the detector, which is similar to the photoelectric effect. In this study, we consider another process, namely, a Compton-like process. As an example, we compare the cross-section of a germanium atom for the absorption process with that of a Compton-like process. Our findin…
We argue that current neutron star observations exclude asymmetric bosonic non-interacting dark matter in the range from 2 keV to 16 GeV, including the 5-15 GeV range favored by DAMA and CoGeNT. If bosonic WIMPs are composite of fermions, the same limits apply provided the compositeness scale is higher than ~10^12 GeV (for WIMP mass ~1 GeV). In case of repulsive self-interactions, we exclude large range of WIMP masses and interaction cross sections which complements the constraints imposed by observations of the Bullet Cluster.
Over the past few decades, an anomalous 511 keV gamma-ray line has been observed from the centre of the Milky Way. Dark matter (DM) in the form of light weakly interacting massive particles (WIMPs) annihilating into electron-positron pairs has been one of the leading hypotheses of the observed emission. Given the small required cross section, a further coupling to lighter particles is required to produce the correct relic density. Here, we derive constraints from the Planck satellite on light WIMPs that were in equilibrium with either the neutrino or electron sector in the early universe. For …
We report results from searches of pseudoscalar and vector bosonic super-weakly interacting massive particles (super-WIMP) in the TEXONO experiment at the Kuo-Sheng Nuclear Power Station, using 314.15 kg days of data from $n$-type Point-Contact Germanium detector. The super-WIMPs are absorbed and deposit total energy in the detector, such that the experimental signatures are spectral peaks corresponding to the super-WIMP mass. Measured data are compatible with the background model, and no significant excess of super-WIMP signals are observed. We derived new upper limits on couplings of electro…
Perturbations due to the planets combined with the non-Coulomb nature of the gravitational potential in the Sun imply that WIMPs that are gravitationally captured by scattering in surface layers of the Sun can evolve into orbits that no longer intersect the Sun. For orbits with a semi-major axis $ < 1/2$ of Jupiter's orbit, such WIMPs can persist in the solar system for $ > 10^9$ years, leading to a previously unanticipated population intersecting Earth's orbit. For WIMPs detectable in the next generation of detectors, this population can provide a complementary signal, in the keV range, to th…
Two germanium detectors are currently operating in the Canfranc Underground Laboratory at 2450 m.w.e looking for WIMP dark matter. One is a 2 kg 76Ge IGEX detector (RG-2) which has an energy threshold of 4 keV and a low-energy background rate of about 0.3 c/keV/kg/day. The other is a small (234 g) natural abundance Ge detector (COSME), of low energy threshold (2.5 keV) and an energy resolution of 0.4 keV at 10 keV which is looking for WIMPs and for solar axions. The analysis of 73 kg-days of data taken by COSME in a search for solar axions via their photon Primakoff conversion and Bragg scatte…
We propose a WIMP candidate with an ``excited state'' 1-2 MeV above the ground state, which may be collisionally excited and de-excites by e+e- pair emission. By converting its kinetic energy into pairs, such a particle could produce a substantial fraction of the 511 keV line observed by INTEGRAL/SPI in the inner Milky Way. Only a small fraction of the WIMPs have sufficient energy to excite, and that fraction drops sharply with galactocentric radius, naturally yielding a radial cutoff, as observed. Even if the scattering probability in the inner kpc is << 1% per Hubble time, enough power is av…
The IGEX Collaboration enriched 76Ge double-beta decay detectors are currently operating in the Canfranc Underground Laboratory with an overburden of 2450 m.w.e. A recent upgrade has made it possible to use them in a search for WIMPs. A new exclusion plot has been derived for WIMP-nucleon spin-independent interaction. To obtain this result, 30 days of data from one IGEX detector, which has an energy threshold of ~4 keV, have been considered. These data improve the exclusion limits derived from other germanium diode experiments in the ~50 GeV DAMA region, and show that with a moderate improveme…
We describe in detail how perturbations due to the planets can cause a sub-population of WIMPs captured by scattering in surface layers of the Sun to evolve to have orbits which no longer intersect the Sun. We argue that such WIMPs, if their orbit has a semi-major axis less than 1/2 of Jupiter's, can persist in the solar system for cosmological timescales. This leads to a new, previously unanticipated WIMP population intersecting the Earth's orbit. The WIMP-nucleon cross sections required for this population to be significant are precisely those in the range predicted for SUSY dark matter, lyi…
We present systematic case studies to investigate the sensitivity of axion searches by liquid xenon detectors, using the axio-electric effect (analogue of the photoelectric effect) on xenon atoms. Liquid xenon is widely considered to be one of the best target media for detection of WIMPs (Weakly Interacting Massive Particles which may form the galactic dark matter) using nuclear recoils. Since these detectors also provide an extremely low radioactivity environment for electron recoils, very weakly-interacting low-mass particles (< 100 keV/c^2), such as the hypothetical axion, could be detected…
Free streaming in a \emph{mixture} of collisionless non-relativistic dark matter (DM) particles is studied by implementing methods from the theory of multicomponent plasmas. The mixture includes Fermionic, condensed and non condensed Bosonic particles decoupling in equilibrium while relativistic, heavy non-relativistic thermal relics (WIMPs), and sterile neutrinos that decouple \emph{out of equilibrium} when they are relativistic. The free-streaming length $λ_{fs}$ is obtained from the marginal zero of the gravitational polarization function, which separates short wavelength Landau-damped from…
In experiments for direct dark matter searches, neutrinos coherently scattering off nuclei can produce similar events as Weakly Interacting Massive Particles (WIMPs). To reach sensitivities better than about 10^-10 pb for the elastic WIMP nucleon spin-independent cross section in the zero-background limit, energy thresholds for nuclear recoils should be >2.05 keV for CaWO_4, >4.91 keV for Ge, >2.89 keV for Xe, >8.62 keV for Ar and >15.93 keV for Ne as target material. Atmospheric neutrinos limit the achievable sensitivity for the background-free direct dark matter search to >10^-12 pb.
Inelastic dark matter, in which WIMP-nucleus scatterings occur through a transition to an excited WIMP state ~ 100 keV above the ground state, provides a compelling explanation of the DAMA annual modulation signal. We demonstrate that the relative sensitivities of various dark matter direct detection experiments are modified such that the DAMA annual modulation signal can be reconciled with the absence of a reported signal at CDMS-Soudan, XENON10, ZEPLIN, CRESST, and KIMS for inelastic WIMPs with masses O(100 GeV). We review the status of these experiments, and make predictions for upcoming on…
Dark matter candidates comprising several sub-states separated by a small mass gap, and coupled to the Standard Model by (sub-)GeV force carriers, can exhibit non-trivial scattering interactions in direct detection experiments. We analyze the secluded U(1)-mediated WIMP scenario, and calculate the elastic and inelastic cross sections for multi-component WIMP scattering off nuclei. We find that second-order elastic scattering, mediated by virtual excited states, provides strong sensitivity to the parameters of the model for a wide range of mass splittings, while for small splittings the WIMP ex…
We explore extensions of inelastic Dark Matter and Magnetic inelastic Dark Matter where the WIMP can scatter to a tower of heavier states. We assume a WIMP mass $m_χ\sim \mathcal{O}(1-100)$ GeV and a constant splitting between successive states $δ\sim\mathcal{O}(1 - 100)$ keV. For the spin-independent scattering scenario we find that the direct experiments CDMS and XENON strongly constrain most of the DAMA/LIBRA preferred parameter space, while for WIMPs that interact with nuclei via their magnetic moment a region of parameter space corresponding to $m_χ\sim 11 $ GeV and $δ< 15$ keV is allowed…
We present results of searches for vector and pseudo-scalar bosonic super-WIMPs, which are dark matter candidates with masses at the keV-scale, with the XENON100 experiment. XENON100 is a dual-phase xenon time projection chamber operated at the Laboratori Nazionali del Gran Sasso. A profile likelihood analysis of data with an exposure of 224.6 live days $\times$ 34\,kg showed no evidence for a signal above the expected background. We thus obtain new and stringent upper limits in the $(8-125)$\,keV/c$^2$ mass range, excluding couplings to electrons with coupling constants of $g_{ae} > 3\times10…
In experiments for direct dark matter searches, neutrinos coherently scattering off nuclei can produce similar events as Weakly Interacting Massive Particles (WIMPs). The calculated count rate for solar neutrinos in such experiments is a few events per ton-year. This count rate strongly depends on the nuclear recoil energy threshold achieved in the experiments for the WIMP search. We show that solar neutrinos can be a serious background source for direct dark matter search experiments using Ge, Ar, Xe and CaWO_4 as target materials. To reach sensitivities better than approximatly 10^-10 pb for…
We study constraints on the models of bosonic super-weakly interacting particle (super-WIMP) dark matter (DM) with DM masses $m_X \sim \mathcal{O}(1 - 100)$ keV from leptonic decays $M\rightarrow \ell \barν_\ell + X$, where $M=B^\pm, D^\pm, D_s^\pm$ is a heavy meson state. We focus on two cases where $X$ denotes either a light pseudoscalar (axion-like), or a light vector state that couples to the standard model (SM) through kinetic mixing. We note that for a small DM mass these decays are separately sensitive to DM couplings to quarks, but not its mass.
XENON100 is a liquid xenon time projection chamber built to search for rare collisions of hypothetical, weakly interacting massive particles (WIMPs), which are candidates for the dark matter in our universe, with xenon atoms. Operated in a low-background shield at the Gran Sasso Underground Laboratory in Italy, XENON100 has reached the unprecedented background level of <0.15 events/(day keV) in the energy range below 100 keV in 30 kg of target mass, before electronic/nuclear recoil discrimination. It found no evidence for WIMPs during a dark matter run lasting for 100.9 live days in 2010, excl…
We explore the reach of low-background experiments made of small quantities of heavy nuclear isotopes in probing the parameter space of inelastic dark matter that is kinematically inaccessible to classic direct detection experiments. Through inelastic scattering with target nuclei, dark matter can yield a signal either via nuclear recoil or nuclear excitation. We present new results based on this approach, using data from low-energy gamma quanta searches in low-background experiments with Hf and Os metal samples, and measurements with CaWO$_4$ and PbWO$_4$ crystals as scintillating bolometers.…
It is shown that weakly interacting massive particles (WIMPs), which are possible cold dark matter candidates, can be studied by exclusive measurements of X-rays following WIMPs nuclear interactions. Inner-shell atomic electrons are ionized through WIMP-nuclear interaction, and then mono-energetic X-rays are emitted when they are filled by outer-shell electrons. The number of inner-shell holes amounts to as large as one per five nuclear recoils for K-shell and several per recoil for L-shell in the case of medium heavy target nuclei interacting with 100-300 GeV WIMPs. Then the K and L X-ray pea…
Proton-philic spin-dependent inelastic Dark Matter is a Weakly Inelastic Massive Particle scenario that can explain the DAMA yearly modulation effect in compliance with the constraints from other direct detection Dark Matter searches. We obtain updated ranges for its parameters both in a halo-independent approach and adopting a truncated Maxwellian for the WIMP velocity distribution constructing approximate frequentist confidence intervals from an effective chi-square including, among others, the latest experimental constraints from XENON1T, PANDAX-II, SuperCDMS and CDMSlite. In the halo-indep…
Increasingly stringent limits from LHC searches for new physics, coupled with lack of convincing signals of weakly interacting massive particle (WIMP) in dark matter searches, have tightly constrained many realizations of the standard paradigm of thermally produced WIMPs as cold dark matter. In this article, we review more generally both thermally and non-thermally produced dark matter (DM). One may classify DM models into two broad categories: one involving bosonic coherent motion (BCM) and the other involving WIMPs. BCM and WIMP candidates need, respectively, some approximate global symmetri…
Tidal streams of the Sagittarius dwarf spheroidal galaxy (Sgr) may be showering dark matter onto the solar system and contributing approx (0.3--23)% of the local density of our Galactic Halo. If the Sagittarius galaxy contains WIMP dark matter, the extra contribution from the stream gives rise to a step-like feature in the energy recoil spectrum in direct dark matter detection. For our best estimate of stream velocity (300 km/sec) and direction (the plane containing the Sgr dwarf and its debris), the count rate is maximum on June 28 and minimum on December 27 (for most recoil energies), and th…
We show that the Weakly Interacting Massive Particle scenario of proton-philic spin-dependent inelastic Dark Matter (pSIDM) can still provide a viable explanation of the observed DAMA modulation amplitude in compliance with the constraints from other experiments after the release of the DAMA/LIBRA-phase2 data and including the recent bound from COSINE-100, that uses the same $NaI$ target of DAMA. The pSIDM scenario provided a viable explanation of DAMA/LIBRA--phase1 both for a Maxwellian WIMP velocity distribution and in a halo-independent approach. At variance with DAMA/LIBRA-phase1, for whic…
Numerous ongoing experiments aim at detecting WIMP dark matter particles from the galactic halo directly through WIMP-nucleon interactions. Once such a detection is established a confirmation of the galactic origin of the signal is needed. This requires a direction-sensitive detector. We show that such a detector can measure the velocity anisotropy beta of the galactic halo. Cosmological N-body simulations predict the dark matter anisotropy to be nonzero, beta~0.2. Baryonic matter has beta=0 and therefore a detection of a nonzero beta would be strong proof of the fundamental difference between…
The recent WMAP and Planck data have confirmed that exotic dark matter together with the vacuum energy (cosmological constant) dominate in the flat Universe. Many extensions of the standard model provide dark matter candidates, in particular Weakly Interacting Massive Particles (WIMPs). %Supersymmetry provides a natural dark matter candidate, the lightest supersymmetric particle (LSP). Thus the direct dark matter detection is central to particle physics and cosmology. Most of the research on this issue has hitherto focused on the detection of the recoiling nucleus. In this paper we study trans…
In direct dark matter detection experiments, conventional elastic scattering of WIMPs results in exponentially falling recoil spectra. In contrast, theories of WIMPs with excited states can lead to nuclear recoil spectra that peak at finite recoil energies E_R. The peaks of such signals are typically fairly broad, with Delta E_R/E_peak ~ 1. We show that in the presence of dark matter structures with low velocity dispersion, such as streams or clumps, peaks from up-scattering can become extremely narrow with FWHM of a few keV only. This differs dramatically from the conventionally expected WIMP…
Dark matter may be hidden, with no standard model gauge interactions. At the same time, in WIMPless models with hidden matter masses proportional to hidden gauge couplings squared, the hidden dark matter's thermal relic density may naturally be in the right range, preserving the key quantitative virtue of WIMPs. We consider this possibility in detail. We first determine model-independent constraints on hidden sectors from Big Bang nucleosynthesis and the cosmic microwave background. Contrary to conventional wisdom, large hidden sectors are easily accommodated. A flavour-free version of the sta…
Models of dark matter with ~ GeV scale force mediators provide attractive explanations of many high energy anomalies, including PAMELA, ATIC, and the WMAP haze. At the same time, by exploiting the ~ MeV scale excited states that are automatically present in such theories, these models naturally explain the DAMA/LIBRA and INTEGRAL signals through the inelastic dark matter (iDM) and exciting dark matter (XDM) scenarios, respectively. Interestingly, with only weak kinetic mixing to hypercharge to mediate decays, the lifetime of excited states with delta < 2 m_e is longer than the age of the unive…
The CoGeNT and CRESST WIMP direct detection experiments have recently observed excesses of nuclear recoil events, while the DAMA/LIBRA experiment has a long standing annual modulation signal. It has been suggested that these excesses may be due to light mass, m_chi ~ 5-10 GeV, WIMPs. The Earth's motion with respect to the Galactic rest frame leads to a directional dependence in the WIMP scattering rate, providing a powerful signal of the Galactic origin of any recoil excess. We investigate whether direct detection experiments with directional sensitivity have the potential to observe this anis…
Probing low mass (sub-GeV -- few GeV) Weakly Interacting Massive Particle (WIMP) candidates of dark matter through WIMP-induced nuclear recoils in direct detection experiments requires use of detector materials consisting of low mass target nuclei and low threshold energy. Here we explore the potential of superheated liquid detectors (SLD) with a hydrogen containing liquid, namely, tetrafluoroethane (C$_{2}$H$_{2}$F$_{4}$) (b.p.~$-26.3^\circ\,$C), as the target material for probing low mass WIMPs. It is found that few-keV level recoil energy thresholds possible for bubble nucleation by WIMP-in…
We investigate the collapse of clusters of weakly interacting massive particles (WIMPs) in the core of a Sun-like star and the possible formation of mini-black holes and the emission of gravitational waves. When the number of WIMPs is small, thermal pressure balances the WIMP cluster's self gravity. If the number of WIMPs is larger than a critical number, thermal pressure cannot balance gravity and the cluster contracts. If WIMPs are collisionless and bosonic, the cluster collapses directly to form a mini-black hole. For fermionic WIMPs, the cluster contracts until it is sustained by Fermi pre…
The XENON100 experiment is the second phase of the XENON program for the direct detection of the dark matter in the universe. The XENON100 detector is a two-phase Time Projection Chamber filled with 161 kg of ultra pure liquid xenon. The results from 224.6 live days of dark matter search with XENON100 are presented. No evidence for dark matter in the form of WIMPs is found, excluding spin-independent WIMP-nucleon scattering cross sections above 2 $\times$ 10$^{-45}$ cm$^2$ for a 55 GeV/c$^2$ WIMP at 90% confidence level (C.L.). The most stringent limit is established on the spin-dependent WIMP…
We explore a two component dark matter model with a fermion and a scalar. In this scenario the Standard Model (SM) is extended by a fermion, a scalar and an additional pseudo scalar. The fermionic component is assumed to have a global ${\rm U(1)}_{\rm DM}$ and interacts with the pseudo scalar via Yukawa interaction while a $\mathbb{Z}_2$ symmetry is imposed on the other component -- the scalar. These ensure the stability of both the dark matter components. Although the Lagrangian of the present model is CP conserving, however the CP symmetry breaks spontaneously when the pseudo scalar acquires…
Multi-component dark matter particles may have a more intricate direct detection signal than simple elastic scattering on nuclei. In a broad class of well-motivated models the inelastic excitation of dark matter particles is followed by de-excitation via $γ$-decay. In experiments with fine energy resolution, such as many $0ν2β$ decay experiments, this motivates a highly model-independent search for the sidereal daily modulation of an unexpected $γ$ line. Such a signal arises from two-step WIMP interaction: the WIMP is first excited in the lead shielding and subsequently decays back to the grou…
We propose a new production mechanism for keV sterile neutrino dark matter which relies neither on the oscillations between sterile and active neutrinos nor on the decay of additional heavier particles. The dark matter neutrinos are instead produced by thermal freeze-out, much like a typical WIMP. The challenge consists in balancing a large Yukawa coupling so that the sterile neutrinos thermalize in the early universe on the one hand, and a small enough Yukawa coupling such that they are stable on cosmological scales on the other. We solve this problem by implementing varying Yukawa couplings.…
We report a systematic study on the directional sensitivity of a direct dark matter detector that detects the polar angle of a recoiling nucleus. A weakly interacting massive particle (WIMP)-mass independent method is used to obtain the sensitivity of a general detector in an isothermal galactic dark matter halo. By using two-dimensional distributions of energy and polar angle, a detector without head-tail information with 6.3 times the statistics is found to achieve the same performance level as a full three-dimensional tracking dark matter detector. Optimum operation orientations are obtaine…
We investigate the possibility for the direct detection of low mass (GeV scale) WIMP dark matter in scintillation experiments. Such WIMPs are typically too light to leave appreciable nuclear recoils, but may be detected via their scattering off atomic electrons. In particular, the DAMA Collaboration [R. Bernabei et al., Nucl. Phys. At. Energy 19, 307 (2018)] has recently presented strong evidence of an annual modulation in the scintillation rate observed at energies as low as 1 keV. Despite a strong enhancement in the calculated event rate at low energies, we find that an interpretation in ter…
We provide a first systematic and quantitative discussion of the phenomenology of the non-relativistic effective Hamiltonian describing the nuclear scattering process for a Weakly Interacting Massive Particle (WIMP) of arbitrary spin $j_χ$. To this aim we obtain constraints from a representative sample of present direct detection experiments assuming the WIMP-nucleus scattering process to be driven by each one of the 44 effective couplings that arise for $j_χ\le$ 2. We find that a high value of the multipolarity $s\le 2 j_χ$ of the coupling, related to the power of the momentum transfer $q$ ap…
A feebly interacting massive particle (FIMP), contrasting with a weakly interacting massive particle (WIMP), is an intriguing dark matter (DM) candidate. Light (keV-scale) FIMP DM is of particular interest: its radiative decay leaves a line signal in x-ray spectra; and it is warm dark matter (WDM) and alters the galactic-scale structure formation of the Universe from that with WIMP DM. Once a possible x-ray line is reported (e.g., $3.5 \,\mathrm{keV}$ line and $7 \,\mathrm{keV}$ FIMP DM is inferred), one has to check whether or not this FIMP DM is compatible with the structure formation. Here …
Weakly Interacting Massive Particles (WIMPs) may constitute most of the matter in the Universe. The ability to detect the directionality of recoil nuclei will considerably facilitate detection of WIMPs. In this paper we propose a novel type of dark matter detector: detectors made of DNA or RNA could provide nanometer resolution for tracking, an energy threshold of 0.5 keV, and can operate at room temperature. When a WIMP from the Galactic Halo elastically scatters off of a nucleus in the detector, the recoiling nucleus then traverses hundreds of strings of single stranded nucleic acids (ssNA) …
We propose a method to identify the direction of an incident Weakly Interacting Massive Particle (WIMP) via induced nuclear recoil. Our method is based on spectroscopic interrogation of quantum defects in macroscopic solid-state crystals . When a WIMP scatters in a crystal, the induced nuclear recoil creates a tell-tale damage cluster, localized to within about 50 nm, with an orientation to the damage trail that correlates well with the direction of the recoil and hence the incoming WIMP. This damage cluster induces strain in the crystal, shifting the energy levels of nearby quantum defects. T…
The XENON100 collaboration has recently released new dark matter limits, placing particular emphasis on their impact on searches known to be sensitive to light-mass (below 10 GeV/c^2) Weakly Interacting Massive Particles (WIMPs), such as DAMA and CoGeNT. We describe here several sources of uncertainty and bias in their analysis that make their new claimed sensitivity presently untenable. In particular, we point out additional work in this field and simple kinematic arguments that indicate that liquid xenon (LXe) may be a relatively insensitive detection medium for the recoil energies (few keV_…
The DAMA experiment searches for Weakly Interacting Massive Particle (WIMP) dark matter via its expected but rare interactions within the detector, where the interaction rates will modulate throughout the year due to the orbital motion of the Earth. Over the course of more than 10 years of operation, DAMA has indeed detected a strong modulation in the event rate above the detector threshold of 2 keVee. Under standard assumptions regarding the dark matter halo and WIMP interactions, this signal is consistent with that expected of WIMPs of two different approximate masses: ~ 10 GeV and ~ 70 GeV.…
The freeze-in mechanism of dark matter production provides a simple and intriguing alternative to the WIMP paradigm. In this paper, we analyze whether freeze-in can be used to account for the dark matter in the so-called singlet fermionic model. In it, the SM is extended with only two additional fields, a singlet scalar that mixes with the Higgs boson, and the dark matter particle, a fermion assumed to be odd under a Z_2 symmetry. After numerically studying the generation of dark matter, we analyze the dependence of the relic density with respect to all the free parameters of the model. These …
The quasiparticle propagation away from the track of a highly ionizing particle in superfluid helium at low temperatures has previously been shown to exhibit anisotropy. We discuss the mechanism responsible for this behavior and show that it occurs for nuclear scattering by dark matter for recoil energies down to a few keV, and perhaps lower. This makes it possible to extend WIMP searches with interaction cross sections that reach into the neutrino floor in a meaningful energy range.
We present the results of the three-month above-ground commissioning run of the Large Underground Xenon (LUX) experiment at the Sanford Underground Research Facility located in Lead, South Dakota, USA. LUX is a 370 kg liquid xenon detector that will search for cold dark matter in the form of Weakly Interacting Massive Particles (WIMPs). The commissioning run, conducted with the detector immersed in a water tank, validated the integration of the various sub-systems in preparation of the underground deployment. Using the data collected, we report excellent light collection properties, achieving …
An emission line with energy of $E\sim 3.5$ keV has been observed in galaxy clusters by two experiments. The emission line is consistent with the decay of a dark matter particle with a mass of $\sim 7$ keV. In this work we discuss the possibility that the dark particle responsible for the emission is a real scalar ($ρ$) which arises naturally in a $U(1)_X$ Stueckelberg of MSSM. In the MSSM Stueckelberg extension $ρ$ couples only to other scalars carrying a $U(1)_X$ quantum number. Under the assumption that there exists a vectorlike leptonic generation carrying both $SU(2)_L\times U(1)_Y$ and $…
Recently, constraints on bosonic asymmetric dark matter have been imposed based on the existence of old neutron stars excluding the dark matter masses in the range from $\sim 2$ keV up to several GeV. The constraints are based on the star destruction scenario where the dark matter particles captured by the star collapse forming a black hole that eventually consumes the host star. In addition, there were claims in the literature that similar constraints can be obtained for dark matter masses heavier than a few TeV. Here we argue that it is not possible to extend to these constraints. We show th…
Superconducting targets have recently been proposed for the direct detection of dark matter as light as a keV, via elastic scattering off conduction electrons in Cooper pairs. Detecting such light dark matter requires sensitivity to energies as small as the superconducting gap of O(meV). Here we show that these same superconducting devices can detect much lighter DM, of meV to eV mass, via dark matter absorption on a conduction electron, followed by emission of an athermal phonon. We demonstrate the power of this setup for relic kinetically mixed hidden photons, pseudoscalars, and scalars, sho…
The low-energy monochromatic neutron emission from an Y-88/Be source can be exploited to mimic the few keVnr nuclear recoils expected from low-mass Weakly Interacting Massive Particles (WIMPs) and coherent scattering of neutrinos off nuclei. Using this source, a ~<10% quenching factor is measured for sodium recoils below 24 keVnr in NaI[Tl]. This is considerably smaller than the 30% typically adopted in the interpretation of the DAMA/LIBRA dark matter experiment, resulting in a marked increase of its tension with other searches, under the standard set of phenomenological assumptions. The metho…
