Weakly Interacting Massive Particle

We report on the observations of 14 dwarf spheroidal galaxies with the Fermi Gamma-Ray Space Telescope taken during the first 11 months of survey mode operations. The Fermi telescope, which is conducting an all-sky γ-ray survey in the 20 MeV to >300 GeV energy range, provides a new opportunity to test particle dark matter models through the expected γ-ray emission produced by pair annihilation of weakly interacting massive particles (WIMPs). Local Group dwarf spheroidal galaxies, the largest galactic substructures predicted by the cold dark

Self-annihilating or decaying dark matter in the Galactic halo might produce high energy neutrinos detectable with neutrino telescopes. We have conducted a search for such a signal using 276 days of data from the IceCube 22-string configuration detector acquired during 2007 and 2008. The effect of halo model choice in the extracted limit is reduced by performing a search that considers the outer halo region and not the Galactic Center. We constrain any large scale neutrino anisotropy and are able to set a limit on the dark matter self-annihilation cross section of σAv ≃ 10 −22 cm 3 s −1 for WIMP masses above 1 TeV, assuming a monochromatic neutrino line spectrum.

ABS1RACf: I review the implications of the Z decay measurements at LEP (and SLC) for the early universe: (a) The Z width measurements, when combined with non-accelerator data rule out GeV range Dirac neutrinos, Majorana neutrinos, and sneutrinos as WIMP dark matter, rule out most explicit "cosmions", and strongly constrain neutralinos. When combined with data from other experiments, this implies that any WIMP is likely to be heavier than 10-20 GeV, and could easily be in the 0(100 GeV-l TeV) region; (b) The limit on Nv, when combined with big-bang nucleosynthesis (BBN) estimates, is consistent with both baryonic and non-baryonic dark matter and allows one to probe the consistency of BBN itself; (c) direct searches for WIMPs will probably require new detectors, sensitive to spin dependent interactions on possibly heavy targets, with event rates which could be 3-4 orders of magnitude smaller than those expected at present detectors; (d) limits on the Higgs and the top quark also have an impact on possible new processes in the early universe.

There is compelling observational evidence for the existence of dark matter. Although knowledge of its underlying nature remains elusive, a variety of theories provide candidate particles [1]. Among those are supersymmetry [2] and universal extra dimensions [3], both of which predict new physics at the electro-weak scale and, in most scenarios, introduce a light, and stable (or long lived) particle that exhibits the properties of a weakly interacting massive particle (WIMP)[4]. WIMPs are an ideal dark matter candidate, predicted to have ...

Despite compelling arguments that significant discoveries of physics beyond the standard model are likely to be made at the Large Hadron Collider, it remains possible that this machine will make no such discoveries, or will make no discoveries directly relevant to the dark matter problem. In this article, we study the ability of astrophysical experiments to deduce the nature of dark matter in such a scenario. In most dark matter studies, the relic abundance and detection prospects are evaluated within the context of some specific particle physics model or models (e.g., supersymmetry). Here, assuming a single weakly interacting massive particle constitutes the universe's dark matter, we attempt to develop a model-independent approach toward the phenomenology of such particles in the absence of any discoveries at the Large Hadron Collider. In particular, we consider generic fermionic or scalar dark matter particles with a variety of interaction forms, and calculate the corresponding constraints from and sensitivity of direct and indirect detection experiments. The results may provide some guidance in disentangling information from future direct and indirect detection experiments.

Dark matter makes up about 23% of matter-energy content of the Universe, other components being the normal baryonic matter and dark energy. Apart from the usual structure of dark matter halo around galaxies, simulations of galaxy formation suggests an additional dark matter component in Milky Way mass galaxies similar to the stellar disk of stars in galaxies. Current detection experiment for dark matter are configured for the standard halo structure. In this work we study how the existence of dark matter disk can effect these experiments. More importantly, we focus on the low energy spectrum of WIMP scattering in direct detection experiments and propose lowered threshold in current experiment which can exploit the effects of dark matter disk, if it indeed exists.

A new calculation of thep/p ratio in cosmic rays is compared to the recent PAMELA data. The good match up to 100 GeV allows to set constraints on exotic contributions from thermal WIMP dark matter candidates. We derive stringent limits on possible enhancements of the WIMP p flux: a mWIMP=100 GeV (1 TeV) signal cannot be increased by more than a factor 6 (40) without overrunning PAMELA data. Annihilation through the W + W − channel is also inspected and crosschecked with e + /(e − + e + ) data. This scenario is strongly disfavored as it fails to simultaneously reproduce positron and antiproton measurements.

We identify 31 dimensionless physical constants required by particle physics and cosmology, and emphasize that both microphysical constraints and selection effects might help elucidate their origin. Axion cosmology provides an instructive example, in which these ...

The ZEPLIN-III experiment in the Palmer Underground Laboratory at Boulby uses a 12 kg two-phase xenon time-projection chamber to search for the weakly interacting massive particles (WIMPs) that may account for the dark matter of our Galaxy. The detector measures both scintillation and ionization produced by radiation interacting in the liquid to differentiate between the nuclear recoils expected from WIMPs and the electron-recoil background signals down to $10 keV nuclear-recoil energy. An analysis of 847 kg Á days of data acquired between February 27, 2008, and May 20, 2008, has excluded a WIMPnucleon elastic scattering spin-independent cross section above 8:1 Â 10 À8 pb at 60 GeVc À2 with a 90% confidence limit. It has also demonstrated that the two-phase xenon technique is capable of better discrimination between electron and nuclear recoils at low-energy than previously achieved by other xenon-based experiments.

These lectures are intended to provide a brief pedagogical review of dark matter for the newcomer to the subject. We begin with a discussion of the astrophysical evidence for dark matter. The standard weakly-interacting massive particle (WIMP) scenario-the motivation, particle models, and detection techniques-is then reviewed. We provide a brief sampling of some recent variations to the standard WIMP scenario as well as some alternatives (axions and sterile neutrinos). Exercises are provided for the reader.

ted liquid iment. This on droplets y nuclear ces since a nsitivity nd pressure. itivity to neutrons, α-particles and γ-rays was determined as a function of these are compared with simulations. In particular, we y in use for atter search at the SNO site to detect WIMPs and discuss possible background sources.

We report on the observations of 14 dwarf spheroidal galaxies with the Fermi Gamma-Ray Space Telescope taken during the first 11 months of survey mode operations. The Fermi telescope provides a new opportunity to test particle dark matter models through the expected gamma-ray emission produced by pair annihilation of weakly interacting massive particles (WIMPs). Local Group dwarf spheroidal galaxies, the

We present the results of a search for point-like sources using 1100 upward-going muons produced by neutrino interactions in the rock below and inside the MACRO detector in the underground Gran Sasso Laboratory. These data show no evidence for a possible neutrino point-like source or for possible correlations between gamma ray bursts and neutrinos. They have been used to set flux upper limits for candidate point-like sources which are in the range 10^-14-10^-15 cm-2 s-1.

The SIMPLE project uses superheated C2ClF5 liquid detectors to search for particle dark matter candidates. We report the results of the first stage exposure (14.1 kgd) of its latest two-stage, Phase II run, with 15 superheated droplet detectors of total active mass 0.208 kg. In combination with the results of the neutron-spin sensitive XENON10 experiment, these results yield a limit of |a_p| < 0.32, |a_n| < 0.17 for M_W = 50 GeV/c2 on the model-independent, spin-dependent sector of weakly interacting massive particle (WIMP)-nucleus interactions, and together yield a 50% reduction in the previously allowed region of the phase space. The result provides a contour minimum of {\sigma}_p ~ 2.8 x 10-2 pb at M_W = 45 GeV/c2, constituting the most restrictive direct detection limit to date against a spin-dependent WIMP-proton coupling. In the spin-independent sector, the result is seen to offer the prospect of contributing to the question of light mass WIMPs with an improvement in the...

We report on the observations of 14 dwarf spheroidal galaxies with the Fermi Gamma-Ray Space Telescope taken during the first 11 months of survey mode operations. The Fermi telescope, which is conducting an all-sky γ-ray survey in the 20 MeV to >300 GeV energy range, provides a new opportunity to test particle dark matter models through the expected γ-ray emission produced by pair annihilation of weakly interacting massive particles (WIMPs). Local Group dwarf spheroidal galaxies, the largest galactic substructures predicted by the cold dark

A new Solar System population of Weakly Interacting Massive Particle (WIMP) dark matter has been proposed to exist. We investigate the implications of this population on indirect signals in neutrino telescopes (due to WIMP annihilations in the Earth) for the case when the WIMP is the lightest neutralino of the MSSM, the minimal supersymmetric extension of the standard model. The velocity distribution and capture rate of this new population is evaluated and the flux of neutrino-induced muons from the center of the Earth in neutrino telescopes is calculated. We show that the effects of the new population can be crucial for masses around 60-120 GeV, where enhancements of the predicted muon flux from the center of the Earth by up to a factor of 100 compared to previously published estimates occur. As a result of the new WIMP population, neutrino telescopes should be able to probe a much larger region of parameter space in this mass range.

NEWAGE is a direction-sensitive dark matter search experiment with a gaseous time-projection chamber. We improved the direction-sensitive dark matter limits by our underground measurement. In this paper, R&D activities sinse the first underground measurement are described.

In addition to a smooth component of weakly interacting massive particle (WIMP) dark matter in galaxies, there may be streams of material; the effects of WIMP streams on direct detection experiments is examined in this paper. The contribution to the count rate due to the stream cuts off at some characteristic energy. Near this cutoff energy, the stream contribution to

In a previous paper [1], we showed how the minimal walking technicolor model (WTC) can provide a composite dark matter candidate, by forming bound states between a −2 electrically charged techniparticle and a 4 He ++. We studied the properties of these techni-O-helium tOHe "atoms", which behave as warmer dark matter rather than cold. In this paper we extend our work on several different aspects. We study the possibility of a mixed scenario where both tOHe and bound states between +2 and −2 electrically charged techniparticles coexist in the dark matter density. We argue that these newly proposed bound states solely made of techniparticles, although they behave as Weakly Interacting Massive Particles (WIMPs), due to their large elastic cross section with nuclei, can only account for a small percentage of the dark matter density. Therefore we conclude that within the minimal WTC, composite dark matter should be mostly composed of tOHe. Moreover in this paper, we put cosmological bounds in the masses of the techniparticles, if they compose the dark matter density. Finally we propose within this setup, a possible explanation of the discrepancy between the DAMA/NaI and DAMA/LIBRA findings and the negative results of CDMS and other direct dark matter searches that imply nuclear recoil measurement, which should accompany ionization.

We present high resolution 240 and 607 MHz GMRT radio observations, complemented with 74 MHz archival VLA radio observations of the Ophiuchus cluster of galaxies, whose radio mini-halo has been recently detected at 1400 MHz. We also present archival Chandra and XMM-Newton data of the Ophiuchus cluster. Our observations do not show significant radio emission from the mini-halo, hence we present upper limits to the integrated, diffuse non-thermal radio emission of the core of the Ophiuchus cluster. The XMM-Newton observations can be well explained by a twotemperature thermal model with temperatures of ≃1.8 keV and ≃9.0 keV, respectively, which confirms previous results that suggest that the innermost central region of the Ophiuchus cluster is a cooling core. This result is consistent with the occurrence of a mini-halo, as expected to be found in hot clusters with cool cores. We also used the XMM-Newton data to set up an upper limit to the (non-thermal) X-ray emission from the cluster. We also emphasize that the non-thermal X-ray emission obtained with XMM-Newton and INTEGRAL cannot be produced by the putative AGN of the galaxy at the cluster center. The combination of available radio and X-ray data has strong implications for the currently proposed models of the spectral energy distribution (SED) from the Ophiuchus cluster. In particular, a synchrotron+IC model is in agreement with the currently available data, if the average magnetic field is in the range (0.02−0.3)µG. A pure WIMP annihilation scenario can in principle reproduce both radio and Xray emission, but at the expense of postulating very large boost factors from dark matter substructures, jointly with extremely low values of the average magnetic field. Finally, a scenario where synchrotron and inverse Compton emission arise from PeV electron-positron pairs (via interactions with the CMB), can be ruled out, as it predicts a non-thermal soft X-ray emission that largely exceeds the thermal Bremsstrahlung measured by INTEGRAL.

The EGRET telescope has identified a gamma-ray source at the Galactic center. We point out here that the spectral features of this source are compatible with the gamma-ray flux induced by pair annihilations of dark matter weakly interacting massive particles (WIMPs). We show that the discrimination between this interpretation and other viable explanations will be possible with GLAST, the next major gamma-ray telescope in space, on the basis of both the spectral and the angular signature of the WIMP-induced component. If, on the other hand, the data will point to an alternative explanation, we prove that there will still be the possibility for GLAST to single out a weaker dark matter source at the Galactic center. The potential of GLAST has been explored both in the context of a generic simplified toymodel for WIMP dark matter, and in a more specific setup, the case of dark matter neutralinos in the minimal supergravity framework. In the latter, we find that even in the case of moderate dark matter densities in the Galactic center region, there are portions of the parameter space which will be probed by GLAST.

Data from the operation of a bubble chamber filled with 3.5 kg of CF3I in a shallow underground site are reported. An analysis of ultrasound signals accompanying bubble nucleations confirms that alpha decays generate a significantly louder acoustic emission than single nuclear recoils, leading to an efficient background discrimination. Three dark matter candidate events were observed during an effective exposure of 28.1 kg-day, consistent with a neutron background. This observation provides the strongest direct detection constraint to date on WIMP-proton spin-dependent scattering for WIMP masses > 20 GeV/c 2 .

ABS1RACf: I review the implications of the Z decay measurements at LEP (and SLC) for the early universe: (a) The Z width measurements, when combined with non-accelerator data rule out GeV range Dirac neutrinos, Majorana neutrinos, and sneutrinos as WIMP dark matter, rule out most explicit "cosmions", and strongly constrain neutralinos. When combined with data from other experiments, this implies that any WIMP is likely to be heavier than 10-20 GeV, and could easily be in the 0(100 GeV-l TeV) region; (b) The limit on Nv, when combined with big-bang nucleosynthesis (BBN) estimates, is consistent with both baryonic and non-baryonic dark matter and allows one to probe the consistency of BBN itself; (c) direct searches for WIMPs will probably require new detectors, sensitive to spin dependent interactions on possibly heavy targets, with event rates which could be 3-4 orders of magnitude smaller than those expected at present detectors; (d) limits on the Higgs and the top quark also have an impact on possible new processes in the early universe.

The ZEPLIN-III experiment in the Palmer Underground Laboratory at Boulby uses a 12 kg two-phase xenon time-projection chamber to search for the weakly interacting massive particles (WIMPs) that may account for the dark matter of our Galaxy. The detector measures both ...

We report results from a blind analysis of the final data taken with the Cryogenic Dark Matter Search experiment (CDMS II) at the Soudan Underground Laboratory, Minnesota, USA. A total raw exposure of 612 kg-days was analyzed for this work. We observed two events in the signal region; based on our background estimate, the probability of observing two or more background events is 23%. These data set an upper limit on the Weakly Interacting Massive Particle (WIMP)-nucleon elastic-scattering spin-independent cross-section of 7.0 × 10 −44 cm 2 for a WIMP of mass 70 GeV/c 2 at the 90% confidence level. Combining this result with all previous CDMS II data gives an upper limit on the WIMP-nucleon spin-independent cross-section of 3.8 × 10 −44 cm 2 for a WIMP of mass 70 GeV/c 2. We also exclude new parameter space in recently proposed inelastic dark matter models.

The SIMPLE project uses superheated C2ClF5 liquid detectors to search for particle dark matter candidates. We report the results of the first stage exposure (14.1 kgd) of its latest two-stage, Phase II run, with 15 superheated droplet detectors of total active mass 0.208 kg. In combination with the results of the neutron-spin sensitive XENON10 experiment, these results yield a limit of |a_p| < 0.32, |a_n| < 0.17 for M_W = 50 GeV/c2 on the model-independent, spin-dependent sector of weakly interacting massive particle (WIMP)-nucleus interactions, and together yield a 50% reduction in the previously allowed region of the phase space. The result provides a contour minimum of {\sigma}_p ~ 2.8 x 10-2 pb at M_W = 45 GeV/c2, constituting the most restrictive direct detection limit to date against a spin-dependent WIMP-proton coupling. In the spin-independent sector, the result is seen to offer the prospect of contributing to the question of light mass WIMPs with an improvement in the...

Data taken during the final shallow-site run of the first tower of the Cryogenic Dark Matter Search (CDMS II) detectors have been reanalyzed with improved sensitivity to small energy depositions. Four ∼224 g germanium and two ∼105 g silicon detectors were operated at the Stanford Underground Facility (SUF) between December 2001 and June 2002, yielding 118 live days of raw exposure. Three of the germanium and both silicon detectors were analyzed with a new low-threshold technique, making it possible to lower the germanium and silicon analysis thresholds down to the actual trigger thresholds of ∼1 keV and ∼2 keV, respectively. Limits on the spin-independent cross section for weakly interacting massive particles (WIMPs) to elastically scatter from nuclei based on these data exclude interesting parameter space for WIMPs with masses below 9 GeV/c 2. Under standard halo assumptions, these data partially exclude parameter space favored by interpretations of the DAMA/LIBRA and CoGeNT experiments' data as WIMP signals, and exclude new parameter space for WIMP masses between 3 GeV/c 2 and 4 GeV/c 2 .

The H.E.S.S. array of Cherenkov telescopes has performed, from 2004 to 2007, a survey of the inner Galactic plane at photon energies above 100 GeV. About 400 hours of data have been accumulated in the region between-30 and +60 degrees in Galactic longitude, and between-3 and +3 degrees in Galactic latitude. Assuming that dark matter is composed of Weakly Interacting Massive Particles, we calculate here the H.E.S.S. sensitivity map for dark matter annihilations, and derive the first experimental constraints on the mini-spikes ′′ scenario, in which a gamma-ray signal arises from dark matter annihilation around Intermediate Mass Black Holes. The data exclude the proposed scenario at a 90% confidence level for dark matter particles with velocity-weighted annihilation cross section σv above 10 −28 cm 3 s −1 and mass between 800 GeV and 10 TeV.

We report the first direct measurements on the energy dependence of the thermal detection efficiency for heavy recoiling nuclei. Two bolometers made by TeO2 crystals facing each other were operated at low temperature and read-out independently, while coincidence-...

The CDMS and EDELWEISS collaborations have combined the results of their direct searches for dark matter using cryogenic germanium detectors. The total data set represents 614 kg•days equivalent exposure. A straightforward method of combination was chosen for its simplicity before data were exchanged between experiments. The results are interpreted in terms of limits on spinindependent WIMP-nucleon cross-section. For a WIMP mass of 90 GeV/c 2 , where this analysis is most sensitive, a cross-section of 3.3 × 10 −44 cm 2 is excluded at 90% CL. At higher WIMP masses, the combination improves the individual limits, by a factor 1.6 above 700 GeV/c 2. Alternative methods of combining the data provide stronger constraints for some ranges of WIMP masses and weaker constraints for others.

XENON10 is an experiment to directly detect weakly interacting massive particle (WIMPs), which may comprise the bulk of the non-baryonic dark matter in our Universe. We report new results for spin-dependent WIMP-nucleon interactions with 129 Xe and 131 Xe from 58.6 live-days of operation at the Laboratori Nazionali del Gran Sasso (LNGS). Based on the non-observation of a WIMP signal in 5.4 kg of fiducial liquid xenon mass, we exclude previously unexplored regions in the theoretically allowed parameter space for neutralinos. We also exclude a heavy Majorana neutrino with a mass in the range of ∼10 GeV/c 2-2 TeV/c 2 as a dark matter candidate under standard assumptions for its density and distribution in the galactic halo.

For the first hme a search for dark matter with lsotoplcally ennched matenal IS done, by using the Ge detectors of the Heidelberg-Moscow expenment A measunng hme of 165 6 kg d IS used to set hmlts on the spin-independent cross section of weakly mteractmg massive parttcles (WIMPS) A background level of 0 102&O 005 events/(kg.d keV) was achieved (average value between 11 keV and 30 keV) It was posstble to extend the exclusion range for Dtrac neutnno masses up to 4lTeV

... Camanzi, MJ Carson, RJ Cashmore, H. Chagani, V. Chepel, D. Cline, D. Davidge, JC Davies, E. Daw, J. Dawson, T. Durkin, B. Edwards, T. Gamble, J. Gao, C. Ghag, AS Howard, WG Jones, M. Joshi, VA Kudryavtsev, T. Lawson, VN Lebedenko, JD Lewin, P. Lightfoot, A. Lindote ...

Assuming that dark matter is a weakly interacting massive particle (WIMP) species X produced in the early Universe as a cold thermal relic, we study the collider signal of pp or pp →XX +jets and its distinguishability from standard-model background processes associated with jets and missing energy. We assume that the WIMP is the sole particle related to dark matter within reach of the LHC-a "maverick" particle-and that it couples to quarks through a higher dimensional contact interaction. We simulate the WIMP final-state signal XX + jets and dominant standard-model (SM) background processes and find that the dark-matter production process results in higher energies for the colored final state partons than do the standard-model background processes. As a consequence, the detectable signature of maverick dark matter is an excess over standard-model expectations of events consisting of large missing transverse energy, together with large leading jet transverse momentum and scalar sum of the transverse momenta of the jets. Existing Tevatron data and forthcoming LHC data can constrain (or discover!) maverick dark matter.

High energy gamma ray astronomy is now a well established field and several sources have been discovered in the region from a few GeV up to several TeV. If sources involving hadronic processes exist, the production of photons would be accompanied by neutrinos too. Other possible neutrino sources could be related to the annihilation of WIMPs at the center of galaxies with black holes. We present the results of a search for point-like sources using 1100 upward-going muons produced by neutrino interactions in the rock below and inside the MACRO detector in the underground Gran Sasso Laboratory. These data show no evidence for a possible neutrino point-like source or for possible correlations between gamma ray bursts and neutrinos. They have been used to set flux upper limits for candidate point-like sources which are in the range 10 −14 − 10 −15 cm −2 s −1 .

Data taken during the final shallow-site run of the first tower of the Cryogenic Dark Matter Search (CDMS II) detectors have been reanalyzed with improved sensitivity to small energy depositions. Four ∼224 g germanium and two ∼105 g silicon detectors were operated at the Stanford Underground Facility (SUF) between December 2001 and June 2002, yielding 118 live days of raw exposure. Three of the germanium and both silicon detectors were analyzed with a new low-threshold technique, making it possible to lower the germanium and silicon analysis thresholds down to the actual trigger thresholds of ∼1 keV and ∼2 keV, respectively. Limits on the spin-independent cross section for weakly interacting massive particles (WIMPs) to elastically scatter from nuclei based on these data exclude interesting parameter space for WIMPs with masses below 9 GeV/c 2. Under standard halo assumptions, these data partially exclude parameter space favored by interpretations of the DAMA/LIBRA and CoGeNT experiments' data as WIMP signals, and exclude new parameter space for WIMP masses between 3 GeV/c 2 and 4 GeV/c 2 .

Using improved Ge and Si detectors, better neutron shielding, and increased counting time, the Cryogenic Dark Matter Search (CDMS) experiment has obtained stricter limits on the cross section of weakly interacting massive particles (WIMPs) elastically scattering from nuclei. Increased discrimination against electromagnetic backgrounds and reduction of the neutron flux confirm WIMPcandidate events previously detected by CDMS were consistent with neutrons and give limits on spin-independent WIMP interactions which are > 2× lower than previous CDMS results for high WIMP mass, and which exclude new parameter space for WIMPs with mass between 8-20 GeV c −2 .

The Cryogenic Dark Matter Search (CDMS) uses low-temperature Ge and Si detectors to search for Weakly Interacting Massive Particles (WIMPs) via their elastic-scattering interaction with atomic nuclei while discriminating against interactions of background particles. CDMS data from 1998 and 1999 with a relaxed fiducial-volume cut (resulting in 15.8 kg-days exposure on Ge) are consistent with an earlier analysis with a more restrictive fiducial-volume cut. Twenty-three WIMP candidate events are observed, but these events are consistent with a background from neutrons. Resulting limits on the spin-independent WIMP-nucleon elastic-scattering crosssection are lower than those of any other experiment for WIMPs with masses between 10-70 GeV c −2. Under the assumptions of standard WIMP interactions and a standard halo, the results are incompatible with the annual-modulation signal of DAMA at 99.99% CL in the asymptotic limit.

A search for a dark matter (DM) annihilation signal into γ-rays toward the direction of the Canis Major (CMa) overdensity is presented. The nature of CMa is still controversial and one scenario represents it as a dwarf galaxy, making it an interesting candidate for DM annihilation searches. A total of 9.6 hours of high quality data were collected with the H.E.S.S. array of Imaging Atmospheric Cherenkov Telescopes (IACTs) and no evidence for a very high energy γ-ray signal is found. Upper limits on the CMa dwarf galaxy mass of the order of 10 9 M ⊙ are derived at the 95% C.L. assuming neutralino masses in the range 500 GeV-10 TeV and relatively large annihilation cross-sections. Constraints on the velocity-weighted annihilation cross section σv , are calculated for specific WIMP scenarios, using a NFW model for the DM halo profile and taking advantage of numerical simulations of hierarchical structure formation. 95% C.L. exclusion limits of the order of 5 × 10 −24 cm 3 s −1 are reached in the 500 GeV-10 TeV DM particle mass interval, assuming a total halo mass of 3 × 10 8 M ⊙ .

Recent measurements of the positron/electron ratio in the cosmic ray (CR) flux exhibits an apparent anomaly 1 , whereby this ratio increases between 10 and 100 GeV. In contrast, this ratio should decrease according to the standard scenario, in which CR positrons are secondaries formed by hadronic interactions between the primary CR protons and the interstellar medium (ISM) 2. The positron excess is therefore interpreted as evidence for either an annihilation/decay of weakly interacting massive particles, or for a direct astrophysical source of pairs. The common feature of all proposed models is that they invoke new physics or new astrophysical sources. However, this line of argumentation relies implicitly on the assumption of a relatively homogeneous CR source distribution. Inhomogeneity of CR sources on a scale of order a kpc, can naturally explain this anomaly. If the nearest major CR source is about a kpc away, then low energy electrons (∼ 1 GeV) can easily reach us. At higher energies (∼ > 10 GeV), the source electrons cool via synchrotron and inverse-Compton before reaching the solar vicinity. Pairs formed in the local vicinity through the proton/ISM interactions can reach the solar system also at high energies, thus increasing the positron/electron ratio. A natural origin of source inhomogeneity is the strong concentration of supernovae to the galactic spiral arms. Assuming supernova remnants (SNRs) as the sole primary source of CRs, and taking into account their concentration near the galactic spiral arms, we consistently predict the observed positron fraction between 1 and 100 GeV, while abiding to different constraints such as the observed electron spectrum and the CRs cosmogenic age. An ATIC 3 like electron spectrum excess at ∼ 600 GeV can be explained, in this picture, as the contribution of a few known nearby SNRs.

The XENON10 experiment at the Gran Sasso National Laboratory uses a 15 kg xenon dual phase time projection chamber (XeTPC) to search for dark matter weakly interacting massive particles (WIMPs). The detector measures simultaneously the scintillation and the ionization produced by radiation in pure liquid xenon, to discriminate signal from background down to 4.5 keV nuclear recoil energy. A blind analysis of 58.6 live days of data, acquired between October 6, 2006 and February 14, 2007, and using a fiducial mass of 5.4 kg, excludes previously unexplored parameter space, setting a new 90% C.L. upper limit for the WIMP-nucleon spin-independent cross-section of 8.8 × 10 −44 cm 2 for a WIMP mass of 100 GeV/c 2 , and 4.5 × 10 −44 cm 2 for a WIMP mass of 30 GeV/c 2. This result further constrains predictions of supersymmetric models.

Despite compelling arguments that significant discoveries of physics beyond the standard model are likely to be made at the Large Hadron Collider, it remains possible that this machine will make no such discoveries, or will make no discoveries directly relevant to the dark matter problem. In this article, we study the ability of astrophysical experiments to deduce the nature of dark matter in such a scenario. In most dark matter studies, the relic abundance and detection prospects are evaluated within the context of some specific particle physics model or models (e.g., supersymmetry). Here, assuming a single weakly interacting massive particle constitutes the universe's dark matter, we attempt to develop a model-independent approach toward the phenomenology of such particles in the absence of any discoveries at the Large Hadron Collider. In particular, we consider generic fermionic or scalar dark matter particles with a variety of interaction forms, and calculate the corresponding constraints from and sensitivity of direct and indirect detection experiments. The results may provide some guidance in disentangling information from future direct and indirect detection experiments.

The H.E.S.S. array of Cherenkov telescopes has performed, from 2004 to 2007, a survey of the inner Galactic plane at photon energies above 100 GeV. About 400 hours of data have been accumulated in the region between-30 and +60 degrees in Galactic longitude, and between-3 and +3 degrees in Galactic latitude. Assuming that dark matter is composed of Weakly Interacting Massive Particles, we calculate here the H.E.S.S. sensitivity map for dark matter annihilations, and derive the first experimental constraints on the mini-spikes ′′ scenario, in which a gamma-ray signal arises from dark matter annihilation around Intermediate Mass Black Holes. The data exclude the proposed scenario at a 90% confidence level for dark matter particles with velocity-weighted annihilation cross section σv above 10 −28 cm 3 s −1 and mass between 800 GeV and 10 TeV.

Despite compelling arguments that significant discoveries of physics beyond the standard model are likely to be made at the Large Hadron Collider, it remains possible that this machine will make no such discoveries, or will make no discoveries directly relevant to the dark matter problem. In this article, we study the ability of astrophysical experiments to deduce the nature of dark matter in such a scenario. In most dark matter studies, the relic abundance and detection prospects are evaluated within the context of some specific particle physics model or models (e.g., supersymmetry). Here, assuming a single weakly interacting massive particle constitutes the universe's dark matter, we attempt to develop a model-independent approach toward the phenomenology of such particles in the absence of any discoveries at the Large Hadron Collider. In particular, we consider generic fermionic or scalar dark matter particles with a variety of interaction forms, and calculate the corresponding constraints from and sensitivity of direct and indirect detection experiments. The results may provide some guidance in disentangling information from future direct and indirect detection experiments.

We investigate whether present data on helioseismology and solar neutrino fluxes may constrain WIMP-matter interactions in the range of WIMP parameters under current exploration in WIMP searches. We find that, for a WIMP mass of 30 GeV, once the effect of the presence of WIMPs in the Sun's interior is maximized, the squared isothermal sound speed is modified, with respect to the standard solar model, by at most 0.4% at the Sun's center. The maximal effect on the 8 B solar neutrino flux is a reduction of 4.5%. Larger masses lead to smaller effects. These results imply that present sensitivities in the measurements of solar properties, though greatly improved in recent years, do not provide information or constraints on WIMP properties of relevance for dark matter. Furthermore, we show that, when current bounds from direct WIMP searches are taken into account, the effect induced by WIMPs with dominant coherent interactions are drastically reduced as compared to the values quoted above. The case of neutralinos in the minimal supersymmetric standard model is also discussed.

Self-annihilating or decaying dark matter in the Galactic halo might produce high energy neutrinos detectable with neutrino telescopes. We have conducted a search for such a signal using 276 days of data from the IceCube 22-string configuration detector acquired during 2007 and 2008. The effect of halo model choice in the extracted limit is reduced by performing a search that considers the outer halo region and not the Galactic Center. We constrain any large scale neutrino anisotropy and are able to set a limit on the dark matter self-annihilation cross section of σAv ≃ 10 −22 cm 3 s −1 for WIMP masses above 1 TeV, assuming a monochromatic neutrino line spectrum.