Dark Matter Particle Mass Research Articles

Low-mass dark matter search results from full exposure of the PandaX-I experiment

We report the results of a weakly-interacting massive particle (WIMP) dark matter search using the full 80.1\;live-day exposure of the first stage of the PandaX experiment (PandaX-I) located in the China Jin-Ping Underground Laboratory. The PandaX-I detector has been optimized for detecting low-mass WIMPs, achieving a photon detection efficiency of 9.6\%. With a fiducial liquid xenon target mass of 54.0\,kg, no significant excess event were found above the expected background. A profile likelihood analysis confirms our earlier finding that the PandaX-I data disfavor all positive low-mass WIMP signals reported in the literature under standard assumptions. A stringent bound on the low mass WIMP is set at WIMP mass below 10\,GeV/c$^2$, demonstrating that liquid xenon detectors can be competitive for low-mass WIMP searches.

Constraining inflationary dark matter in the luminogenesis model

Using renormalization-group flow and cosmological constraints on inflation models, we exploit a unique connection between cosmological inflation and the dynamical mass of dark matter particles in the luminogenesis model, a unification model with the gauge group SU(3)C × SU(6) × U(1)Y, which breaks to the Standard Model with an extra gauge group for dark matter when the inflaton rolls into the true vacuum. In this model, inflaton decay gives rise to dark matter, which in turn decays to luminous matter in the right proportion that agrees with cosmological data. Some attractive features of this model include self-interacting dark matter, which may resolve the problems of dwarf galaxy structures and dark matter cusps at the centers of galaxies.

Directional dark matter searches with carbon nanotubes

A new solution to the problem of dark matter directional detection might come from the use of large arrays of aligned carbon nanotubes. We calculate the expected rate of carbon ions channeled in single-wall nanotubes once extracted by the scattering with a massive dark matter particle. Depending on its initial kinematic conditions, the ejected Carbon ion may be channeled in the nanotube array or stop in the bulk. The orientation of the array with respect to the direction of motion of the Sun has an appreciable effect on the channeling probability. This provides the required anisotropic response for a directional detector.

Cold or warm? Constraining dark matter with primeval galaxies and cosmic reionization after Planck

Dark matter constitutes the great majority of the matter content in the Universe, but its microscopic nature remains an intriguing mystery, with profound implications for particle physics, astrophysics and cosmology. Here we shed light on the longstanding issue of whether the dark matter is warm or cold by combining the measurements of the galaxy luminosity functions out to high redshifts 0z∼ 1 from the Hubble Space Telescope with the recent cosmological data on the reionization history of the Universe from the Planck mission. We derive robust and tight bounds on the mass of warm dark matter particle, finding that the current data require it to be in the narrow range between 2 and 3 keV . In addition, we show that a mass not exceeding 3 keV is also concurrently indicated by astrophysical constraints related to the local number of satellites in Milky Way-sized galaxies, though it is in marginal tension with analysis of the Lyman-α forest. For warm dark matter masses above 3 keV as well as for cold dark matter, to satisfy the Planck constraints on the optical depth and not to run into the satellite problem would require invoking astrophysical processes that inhibit galaxy formation in halos with mass MH ≲ few × 10 8 M⊙, corresponding to a limiting UV magnitude MUV≈ −11. Anyway, we predict a downturn of the galaxy luminosity function at z∼ 8 faintward of MUV≈ −12, and stress that its detailed shape is extremely informative both on particle physics and on the astrophysics of galaxy formation in small halos. These expectations will be tested via the Hubble Frontier Fields and with the advent of the James Webb Space Telescope, which will enable probing the very faint end of the galaxy luminosity function out to z ∼ 8–10.

Limits on dark matter annihilation signals from the Fermi LAT 4-year measurement of the isotropic gamma-ray background

We search for evidence of dark matter (DM) annihilation in the isotropic gamma-ray background (IGRB) measured with 50 months of Fermi Large Area Telescope (LAT) observations. An improved theoretical description of the cosmological DM annihilation signal, based on two complementary techniques and assuming generic weakly interacting massive particle (WIMP) properties, renders more precise predictions compared to previous work. More specifically, we estimate the cosmologically-induced gamma-ray intensity to have an uncertainty of a factor ∼ 20 in canonical setups. We consistently include both the Galactic and extragalactic signals under the same theoretical framework, and study the impact of the former on the IGRB spectrum derivation. We find no evidence for a DM signal and we set limits on the DM-induced isotropic gamma-ray signal. Our limits are competitive for DM particle masses up to tens of TeV and, indeed, are the strongest limits derived from Fermi LAT data at TeV energies. This is possible thanks to the new Fermi LAT IGRB measurement, which now extends up to an energy of 820 GeV. We quantify uncertainties in detail and show the potential this type of search offers for testing the WIMP paradigm with a complementary and truly cosmological probe of DM particle signals.

Cosmological models with running cosmological term and decaying dark matter

We investigate the dynamics of the generalized $\Lambda$CDM model, which the $\Lambda$ term is running with the cosmological time. The $\Lambda(t)$ term emerges from the covariant theory of the scalar field $\phi$ with the self-interacting potential $V(\phi)$. On the example of the model $\Lambda(t)=\Lambda_{\text{bare}}+\frac{\alpha^2}{t^2}$ we show the existence of a mechanism of the modification of the scaling law for energy density of dark matter: $\rho_{\text{dm}}\propto a^{-3+\lambda(t)}$. We discuss the evolution of $\Lambda(t)$ term and pointed out that during the cosmic evolution there is a long phase in which this term is approximately constant. This effect justifies Alcaniz and Lima's approach to $\Lambda(H)$ cosmologies. We also present the statistical analysis of both the $\Lambda(t)$CDM model with dark energy and decaying dark matter and the $\Lambda$CDM standard cosmological model. We divide the observational data into two groups: low $z$ data (SNIa, BAO, $H(z)$ and AP test) and high $z$ data (Planck, WP and lensing). While for the former we find the best fit value of the parameter $\lambda$ is positive ($\lambda=0.0338$, energy transfer is from the dark energy to dark matter sector), for the latter we find that $\lambda$ is $-0.0199$ which is an evidence that the energy transfer is from decaying dark matter. This disagreement correlates with estimated values of $H_0$ ($67.77$ km/(s Mpc) and $65.62$ km/(s Mpc) respectively). The decaying dark matter causes to lowering a mass of dark matter particles which are lighter than CDM particles and remain relativistic. The rate of the process of decaying matter is estimated. We show that in the models of decaying dark matter, the cosmological constant problem disappears naturally. The model with decaying dark matter possesses one parameter more but in light of the AIC it is better than the $\Lambda$CDM standard cosmological model.

Constraining condensate dark matter in galaxy clusters

We constrain scattering length parameters in a Bose-Einstein condensate dark matter model by using galaxy clusters radii, with the implementation of a method previously applied to galaxies. At the present work, we use a sample of 114 clusters radii in order to obtain the scattering lengths associated with a dark matter particle mass in the range $10^{-6}-10^{-4}\, {\rm eV}$. We obtain scattering lengths that are five orders of magnitude larger than the ones found in the galactic case, even when taking into account the cosmological expansion in the cluster scale by means of the introduction of a small cosmological constant. We also construct and compare curves for the orbital velocity of a test particle in the vicinity of a dark matter cluster in both the expanding and the non-expanding cases.

A simulation-based study of the neutron backgrounds for NaI dark matter experiments

Among the direct search experiments for weakly interacting massive particle (WIMP) dark matter, the DAMA experiment observed an annual modulation signal interpreted as WIMP interactions with a significance of 9.2σ. Recently, Jonathan Davis claimed that the DAMA modulation may be interpreted on the basis of the neutron scattering events induced by the muons and neutrinos together. We tried to simulate the neutron backgrounds at the Gran Sasso and Yangyang laboratory with and without the polyethylene shielding to quantify the effects of the ambient neutrons on the direct detection experiments based on the crystals.

Direct Detection of Dark Matter with Resonant Annihilation* *Supported by the National Basic Research Program of China (973 Program) under Grant No. 2010CB833000; the National Nature Science Foundation of China (NSFC) under Grant Nos. 10975170, 10821504, 10905084, and 11335012; and the Project of Knowledge Innovation Program (PKIP) of the Chinese Academy of Science

In the scenario where the dark matter (DM) particles pair annihilate through a resonance particle R, the constraint from DM relic density makes the corresponding cross section for DM-nuclei elastic scattering extremely small, and can be below the neutrino background induced by the coherent neutrino-nuclei scattering, which makes the DM particle beyond the reach of the conventional DM direct detection experiments. We present an improved analytical calculation of the DM relic density in the case of resonant DM annihilation for s- and p-wave cases and invesitgate the condition for the DM-nuclei scattering cross section to be above the neutrino background. We show that in Higgs-portal type models, for DM particles with s-wave annihilation, the spin-independent DM-nucleus scattering cross section is proportional to ΓR/mR, the ratio of the decay width and the mass of R. For a typical DM particle mass ∼ 50 GeV, the condition leads to . In p-wave annihilation case, the spin-independent scattering cross section is insensitive to ΓR/mR, and is always above the neutrino background, as long as the DM particle is lighter than the top quark. The real singlet DM model is discussed as a concrete example.

Dark matter annihilation in the first galaxy haloes

We investigate the impact of energy released from self-annihilating dark matter (DM) on heating of gas in the small, high-redshift DM haloes thought to host the first stars. A super-symmetric (SUSY)-neutralino-like particle is implemented as our DM candidate. The PYTHIA code is used to model the final, stable particle distributions produced during the annihilation process. We use an analytic treatment in conjunction with the code MEDEA2 to find the energy transfer and subsequent partition into heating, ionizing and Lyman α photon components. We consider a number of halo density models, DM particle masses and annihilation channels. We find that the injected energy from DM exceeds the binding energy of the gas within a 105-106 M⊙ halo at redshifts above 20, preventing star formation in early haloes in which primordial gas would otherwise cool. Thus we find that DM annihilation could delay the formation of the first galaxies.

Dark matter for excess of AMS-02 positrons and antiprotons

We propose a dark matter explanation to simultaneously account for the excess of antiproton-to-proton and positron power spectra observed in the AMS-02 experiment while having the right dark matter relic abundance and satisfying the current direct search bounds. We extend the Higgs triplet model with a hidden gauge symmetry of SU(2)X that is broken to Z3 by a quadruplet scalar field, rendering the associated gauge bosons stable weakly-interacting massive particle dark matter candidates. By coupling the complex Higgs triplet and the SU(2)X quadruplet, the dark matter candidates can annihilate into triplet Higgs bosons each of which in turn decays into lepton or gauge boson final states. Such a mechanism gives rise to correct excess of positrons and antiprotons with an appropriate choice of the triplet vacuum expectation value. Besides, the model provides a link between neutrino mass and dark matter phenomenology.

Cosmology beyond the standard model: Multi-component dark matter model

We show that both the mass and composition of dark matter (DM) particles strongly influence the formation of low mass DM halos. Comparison of theoretical predictions with observations allows us to select the more promising DM models. More details can be found in our paper arXiv:1404.3362.

Probing WIMP particle physics and astrophysics with direct detection and neutrino telescope data

With positive signals from multiple direct detection experiments it will, in principle, be possible to measure the mass and cross sections of weakly-interacting massive particle (WIMP) dark matter. Recent work has shown that, with a polynomial parameterisation of the WIMP speed distribution, it is possible to make an unbiased measurement of the WIMP mass, without making any astrophysical assumptions. However, direct detection experiments are not sensitive to low-speed WIMPs and, therefore, any model-independent approach will lead to a bias in the cross section. This problem can be solved with the addition of measurements of the flux of neutrinos from the Sun. This is because the flux of neutrinos produced from the annihilation of WIMPs which have been gravitationally captured in the Sun is sensitive to low-speed WIMPs. Using mock data from next-generation direct detection experiments and from the IceCube neutrino telescope, we show that the complementary information from IceCube on low-speed WIMPs breaks the degeneracy between the cross section and the speed distribution. This allows unbiased determinations of the WIMP mass and spin-independent and spin-dependent cross sections to be made, and the speed distribution to be reconstructed. We use two parameterisations of the speed distribution: binned and polynomial. While the polynomial parameterisation can encompass a wider range of speed distributions, this leads to larger uncertainties in the particle physics parameters.

Search for gamma-ray emission from dark matter annihilation in the large magellanic cloud with the fermi large area telescope

At a distance of 50 kpc and with a dark matter mass of $\sim10^{10}$ M$_{\odot}$, the Large Magellanic Cloud (LMC) is a natural target for indirect dark matter searches. We use five years of data from the Fermi Large Area Telescope (LAT) and updated models of the gamma-ray emission from standard astrophysical components to search for a dark matter annihilation signal from the LMC. We perform a rotation curve analysis to determine the dark matter distribution, setting a robust minimum on the amount of dark matter in the LMC, which we use to set conservative bounds on the annihilation cross section. The LMC emission is generally very well described by the standard astrophysical sources, with at most a $1-2\sigma$ excess identified near the kinematic center of the LMC once systematic uncertainties are taken into account. We place competitive bounds on the dark matter annihilation cross section as a function of dark matter particle mass and annihilation channel.

Search for dark matter, extra dimensions, and unparticles in monojet events in proton-proton collisions at [Formula: see text][Formula: see text

Results are presented from a search for particle dark matter (DM), extra dimensions, and unparticles using events containing a jet and an imbalance in transverse momentum. The data were collected by the CMS detector in proton–proton collisions at the LHC and correspond to an integrated luminosity of 19.7,text {fb}^text {-1}at a centre-of-mass energy of 8,{mathrm{TeV}},. The number of observed events is found to be consistent with the standard model prediction. Limits are placed on the DM-nucleon scattering cross section as a function of the DM particle mass for spin-dependent and spin-independent interactions. Limits are also placed on the scale parameter M_mathrm {D} in the Arkani-Hamed, Dimopoulos, and Dvali (ADD) model of large extra dimensions, and on the unparticle model parameter {{Lambda _mathrm{U}}} . The constraints on ADD models and unparticles are the most stringent limits in this channel and those on the DM-nucleon scattering cross section are an improvement over previous collider results.

Dark matter searches in CMS

The CMS collaboration searched for Dark Matter (DM) particles produced in pairs in proton-proton (pp) collisions performed by the LHC at a centre-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 19.7 /fb. The following signatures were investigated: a single boosted object and a significant transverse momentum imbalance; associated production of DM with a pair of top quarks; decay of a Higgs boson (H) into a pair of DM particles. Exclusion limits were set on the cross sections of DM production and interaction cross sections, as a function of the DM particle mass.

Comprehensive search for dark matter annihilation in dwarf galaxies

We present a new formalism designed to discover dark matter annihilation occurring in the Milky Way's dwarf galaxies. The statistical framework extracts all available information in the data by simultaneously combining observations of all the dwarf galaxies and incorporating the impact of particle physics properties, the distribution of dark matter in the dwarfs, and the detector response. The method performs maximally powerful frequentist searches and produces confidence limits on particle physics parameters. Probability distributions of test statistics under various hypotheses are constructed exactly, without relying on large sample approximations. The derived limits have proper coverage by construction and claims of detection are not biased by imperfect background modeling. We implement this formalism using data from the Fermi Gamma-ray Space Telescope to search for an annihilation signal in the complete sample of Milky Way dwarfs whose dark matter distributions can be reliably determined. We find that the observed data is consistent with background for each of the dwarf galaxies individually as well as in a joint analysis. The strongest constraints are at small dark matter particle masses. Taking the median of the systematic uncertainty in dwarf density profiles, the cross section upper limits are below the pure s-wave weak scale relic abundance value (2.2 x 10^-26 cm^3/s) for dark matter masses below 26 GeV (for annihilation into b quarks), 29 GeV (tau leptons), 35 GeV (up, down, strange, and charm quarks and gluons), 6 GeV (electrons/positrons), and 114 GeV (two-photon final state). For dark matter particle masses less than 1 TeV, these represent the strongest limits obtained to date using dwarf galaxies.

The effect of dark matter resolution on the collapse of baryons in high-redshift numerical simulations

We examine the impact of dark matter particle resolution on the formation of a baryonic core in high resolution adaptive mesh refinement simulations. We test the effect that both particle smoothing and particle splitting have on the hydrodynamic properties of a collapsing halo at high redshift (z > 20). Furthermore, we vary the background field intensity, with energy below the Lyman limit (< 13.6 eV), as may be relevant for the case of metal-free star formation and super-massive black hole seed formation. We find that using particle splitting methods greatly increases our particle resolution without introducing any numerical noise and allows us to achieve converged results over a wide range of external background fields. Additionally, we find that for lower values of the background field a lower dark matter particle mass is required. We define the radius of the core as the point at which the enclosed baryonic mass dominates over the enclosed dark matter mass. For our simulations this results in $\rm{R_{core} \sim 5\ pc}$. We find that in order to produce converged results which are not affected by dark matter particles requires that the relationship ${M_{\rm{core}} / M_{\rm{DM}}} > 100.0$ be satisfied, where ${M_{\rm{core}}}$ is the enclosed baryon mass within the core and $M_{\rm{DM}}$ is the minimum dark matter particle mass. This ratio should provide a very useful starting point for conducting convergence tests before any production run simulations. We find that dark matter particle smoothing is a useful adjunct to already highly resolved simulations.

Atomic limits in the search for galactic dark matter

Direct searches for low mass dark matter particles via scattering off target nuclei require detection of recoiling atoms with energies of ~1 keV or less. The amount of electronic excitation produced by such atoms is quenched relative to a recoiling electron of the same energy. The Lindhard model of this quenching, as originally formulated, remains widely used after more than 50 years. The present work shows that for very small energies, a simplifying approximation of that model must be removed. Implications for the sensitivity of direct detection experiments are discussed.

Constraining dark matter in the LRTH model with latest LHC, XENON100 and LUX data

In the left–right twin Higgs (LRTH) model, the neutral is a candidate for weakly interacting massive particle dark matter (DM). If its mass is lighter than half of the standard model-like Higgs boson h, the new invisible decay will become open. In this paper, we examine the status of a light DM () under current experimental constraints including the latest LHC Higgs data, the XENON100 and LUX limit on the DM scattering off the nucleon. The following observations have been obtained: (i) the current ATLAS (CMS) measurements of can exclude the invisible Higgs branching ratio larger than 34% (48%) at level; (ii) the Global fits to the latest LHC and Tevatron Higgs data provide a stronger constraint: (30%) at () level, which could be tested in the LHC experiments; (iii) for the spin-independent scattering cross section off the nucleon, the recent XENON100 (LUX) data can exclude the invisible decay rate larger than 50% (25%); and (iv) the results of direct DM searches with LUX can give strong constraint on the viable parameter space of in this LRTH model.