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Title: Dark matter in the solar system III: The distribution function of WIMPs at the Earth from gravitational capture
Authors: Annika H. G. Peter

In this last paper in a series of three on weakly interacting massive particle (WIMP) dark matter in the solar system, we focus on WIMPs bound to the system by gravitationally scattering off of planets. We present simulations of WIMP orbits in a toy solar system consisting of only the Sun and Jupiter. As previous work suggested, we find that the density of gravitationally captured WIMPs at the Earth is small and largely insensitive to the details of elastic scattering in the Sun. However, we find that the density of gravitationally captured WIMPs may be affected by external Galactic gravitational fields. If such fields are unimportant, the density of gravitationally captured WIMPs at the Earth should be similar to the maximum density of WIMPs captured in the solar system by elastic scattering in the Sun. Using standard assumptions about the halo WIMP distribution function, we find that the gravitationally captured WIMPs contribute negligibly to direct detection event rates. While these WIMPs do dominate the annihilation rate of WIMPs in the Earth, the resulting event rate in neutrino telescopes is too low to be observed in next-generation neutrino telescopes.

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Title: Dark matter in the solar system II: WIMP annihilation rates in the Sun
Authors: Annika H. G. Peter

We calculate the annihilation rate of weakly interacting massive particles (WIMPs) in the Sun as a function of their mass and elastic scattering cross section. One by-product of the annihilation, muon neutrinos, may be observed by the next generation of neutrino telescopes. Previous estimates of the annihilation rate assumed that any WIMPs from the Galactic dark halo that are captured in the Sun by elastic scattering off solar nuclei quickly reach thermal equilibrium in the Sun. We show that the optical depth of the Sun to WIMPs and the gravitational forces from planets both serve to decrease the annihilation rate below these estimates. While we find that the sensitivity of upcoming km≥-scale neutrino telescopes to ~100 GeV WIMPs is virtually unchanged from previous estimates, the sensitivity of these experiments to ~10 TeV WIMPs may be an order of magnitude less than the standard calculations would suggest. The new estimates of the annihilation rates should guide future experiment design and improve the mapping from neutrino event rates to WIMP parameter space.

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Title: Dark matter in the solar system I: The distribution function of WIMPs at the Earth from solar capture
Authors: Annika H. G. Peter

The next generation of dark matter (DM) direct detection experiments and neutrino telescopes will probe large swaths of dark matter parameter space. In order to interpret the signals in these experiments, it is necessary to have good models of both the halo DM streaming through the solar system and the population of DM bound to the solar system. In this paper, the first in a series of three on DM in the solar system, we present simulations of orbits of DM bound to the solar system by solar capture in a toy solar system consisting of only the Sun and Jupiter, assuming that DM consists of a single species of weakly interacting massive particle (WIMP). We describe how the size of the bound WIMP population depends on the WIMP mass, spin-independent cross section, and spin-dependent cross section. Using a standard description of the Galactic DM halo, we find that the maximum enhancement to the direct detection event rate, consistent with current experimental constraints on the WIMP-nucleon cross section, is < 1% relative to the event rate from halo WIMPs, while the event rate from neutrinos from WIMP annihilation in the center of the Earth is unlikely to meet the threshold of next-generation, km≥-sized (IceCube, KM3NeT) neutrino telescopes.

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Tendrils of dark matter channelled gas deep into the hearts of some of the universe's earliest galaxies, a new computer simulation suggests. The result could explain how some massive galaxies created vast numbers of stars without gobbling up their neighbours.
Dramatic bursts of star formation are thought to occur when galaxies merge and their gas collides and heats up. Evidence of these smash-ups is fairly easy to spot, since they leave behind mangled pairs of galaxies that eventually merge, their gas settling into a bright, compact centre.

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Title: Dark Matter
Authors: Jaan Einasto

A review of the development of the concept of dark matter is given. I begin the review with the description of the discovery of the mass paradox in our Galaxy and in clusters of galaxies. In mid 1970s the amount of observational data was sufficient to suggest the presence of a massive and invisible population around galaxies and in clusters of galaxies. The nature of the dark population was not clear at that time, but the hypotheses of stellar as well as of gaseous nature of the new population had serious difficulties. These difficulties disappeared when non-baryonic nature of dark matter was suggested in early 1980s. In addition to the presence of Dark Matter, recent observations suggest the presence of Dark Energy, which together with Dark Matter and ordinary baryonic matter makes the total matter/energy density of the Universe equal to the critical cosmological density. There are various hypothesis as for the nature of the dark matter particles, and generally some form of weakly interactive massive particles (WIMPs) are strongly favoured. Both Dark Matter and Dark Energy are the greatest challenges for modern physics since their nature is unknown.

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For the past quarter century, dark matter has been a mystery we've just had to live with. But the time may be getting close when science can finally unveil what this befuddling stuff is that makes up most of the matter in the universe.

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Dark matter detector
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New detector will aid dark matter search
Several research projects are underway to try to detect particles that may make up the mysterious "dark matter" believed to dominate the universe's mass. But the existing detectors have a problem: They also pick up particles of ordinary matter -- hurtling neutrons that masquerade as the elusive dark-matter particles the instruments are designed to find.
MIT physicist Jocelyn Monroe has a solution. A new detector she and her students have built just finished its initial testing last week at Los Alamos National Laboratory. When deployed in the next few months alongside one of the existing dark-matter detectors, the new device should identify all of the ordinary neutrons that come along, leaving anything else that the other detector picks up as a strong candidate for the elusive dark matter.

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Title: Result from the First Science Run of the ZEPLIN-III Dark Matter Search Experiment
Authors: V. N. Lebedenko, H. M. Araujo, E. J. Barnes, A. Bewick, R. Cashmore, V. Chepel, D. Davidge, J. Dawson, T. Durkin, B. Edwards, C. Ghag, V. Graffagnino, M. Horn, A. S. Howard, A. J. Hughes, W. G. Jones, M. Joshi, G. E. Kalmus, A. G. Kovalenko, A. Lindote, I. Liubarsky, M. I. Lopes, R. Luscher, P. Majewski, A. StJ. Murphy, F. Neves, J. Pinto da Cunha, R. Preece, J. J. Quenby, P. R. Scovell, C. Silva, V. N. Solovov, N. J. T. Smith, P. F. Smith, V. N. Stekhanov, T. J. Sumnery, C. Thorne, R. J. Walker

The ZEPLIN-III experiment in the Palmer Underground Laboratory at Boulby uses a 12kg 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 ionisation produced by radiation interacting in the liquid to differentiate between the nuclear recoils expected from WIMPs and the electron recoil background signals down to ~10keV nuclear recoil energy. An analysis of 847kg.days of data acquired between February 27th 2008 and May 20th 2008 has excluded a WIMP-nucleon elastic scattering spin-independent cross-section above 7.7x10(-8)pb at 55GeV/c2 with a 90% confidence limit.

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Universe's dark matter mix is 'just right' for life
It's not just the nature of dark matter that's a mystery - even its abundance is inexplicable. But if our universe is just one of many possible universes, at least this conundrum can be explained.
The total amount of dark matter - the unseen stuff thought to make up most of the mass of the universe - is five to six times that of normal matter. This difference sounds pretty significant, but it could have been much greater, because the two types of matter probably formed via radically different processes shortly after the big bang. The fact that the ratio is so conducive to a life-bearing universe "looks like a tremendous coincidence", says Raphael Bousso at the University of California, Berkeley.

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Is a new force at work in the dark sector?
New theory tries to explain latest dark-matter search results

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