Dark Matter Subhalos In the Fermi First Source Catalog

The Milky Way's dark matter halo is thought to contain large numbers of smaller subhalos. These objects can contain very high densities of dark matter, and produce potentially observable fluxes of gamma rays. In this article, we study the gamma ray sources in the Fermi Gamma Ray Space Telescope's recently published First Source Catalog, and attempt to determine whether this catalog might contain a population of dark matter subhalos. We find that, while approximately 20-60 of the catalog's unidentified sources could plausibly be dark matter subhalos, such a population cannot be clearly identified as such at this time. From the properties of the sources in the First Source Catalog, we derive limits on the dark matter's annihilation cross section that are comparably stringent to those derived from recent observations of dwarf spheroidal galaxies.Comment: 11 pages, 9 figures V2: Minor errors in Figure 3 correcte

Searching For Dark Matter Subhalos In the Fermi-LAT Second Source Catalog

The dark matter halo of the Milky Way is expected to contain an abundance of smaller subhalos. These subhalos can be dense and produce potentially observable fluxes of gamma rays. In this paper, we search for dark matter subhalo candidates among the sources in the Fermi-LAT Second Source Catalog which are not currently identified or associated with counterparts at other wavelengths. Of the nine high-significance, high-latitude (|b|>60 degrees), non-variable, unidentified sources contained in this catalog, only one or two are compatible with the spectrum of a dark matter particle heavier than approximately 50-100 GeV. The majority of these nine sources, however, feature a spectrum that is compatible with that predicted from a lighter (~5-40 GeV) dark matter particle. This population is consistent with the number of observable subhalos predicted for a dark matter candidate in this mass range and with an annihilation cross section of a simple thermal relic (sigma v~3x10^{-26} cm^3/s). Observations in the direction of these sources at other wavelengths will be necessary to either reveal their astrophysical nature (as blazars or other active galactic nuclei, for example), or to further support the possibility that they are dark matter subhalos by failing to detect any non-gamma ray counterpart.Comment: 8 pages, 4 figure

Implications of a 130 GeV Gamma-Ray Line for Dark Matter

Recent reports of a gamma-ray line feature at ~130 GeV in data from the Fermi Gamma-Ray Space Telescope have generated a great deal of interest in models in which dark matter particles annihilate with a sizable cross section to final states including photons. In this article, we take a model-independent approach, and discuss a number of possibilities for dark matter candidates which could potentially generate such a feature. While we identify several scenarios which could lead to such a gamma-ray line, these models are each fairly constrained. In particular, viable models require large couplings (g>1-3), and additional charged particles with masses in the range of approximately ~130-200 GeV. Furthermore, lower energy gamma-ray constraints from the Galactic Center force us to consider scenarios in which the dark matter annihilates in the early universe through velocity-suppressed processes, or to final states which yield relatively few gamma-rays (such as electrons, muons or neutrinos). An exception to these conclusions can be found in models in which the dark matter annihilates to heavy intermediate states which decay to photons to generate a line-like gamma-ray spectrum.Comment: 7 pages, 4 figure

Light Z' Bosons at the Tevatron

New gauge bosons with Standard Model-like couplings to leptons are constrained by collider searches to be heavier than approximately ~1 TeV. A Z' boson with suppressed couplings to leptons, however, could be much lighter and possess substantial couplings to Standard Model quarks. In this article, we consider a new leptophobic Z' gauge boson as a simple and well motivated extension of the Standard Model, and discuss several of its possible signatures at the Tevatron. We find that three of the recent anomalies reported from the Tevatron - in particular the top-quark forward-backward asymmetry and excesses in the 3b and W + 2 jets final states - could be explained by a new Z' with a mass of approximately 150 GeV, relatively large couplings to quarks, and suppressed couplings to electrons and muons. Moreover, we find that such a particle could also mediate the interactions of dark matter, leading to potentially interesting implications for direct detection experiments.Comment: 12 pages, 7 figures. v2, v3: updated references. v4: updated to match published version, including minor revisions to figures 1 and

The Sensitivity of the IceCube Neutrino Detector to Dark Matter Annihilating in Dwarf Galaxies

In this paper, we compare the relative sensitivities of gamma-ray and neutrino observations to the dark matter annihilation cross section in leptophilic models such as have been designed to explain PAMELA data. We investigate whether the high energy neutrino telescope IceCube will be competitive with current and upcoming searches by gamma-ray telescopes, such as the Atmospheric Cerenkov Telescopes (ACTs) (HESS, VERITAS and MAGIC), or the Fermi Gamma Ray Space Telescope, in detecting or constraining dark matter particles annihilating in dwarf spheroidal galaxies. We find that after ten years of observation of the most promising nearby dwarfs, IceCube will have sensitivity comparable to the current sensitivity of gamma-ray telescopes only for very heavy (m_X > 7 TeV) or relatively light (m_X < 200 GeV) dark matter particles which annihilate primarily to mu+mu-. If dark matter particles annihilate primarily to tau+tau-, IceCube will have superior sensitivity only for dark matter particle masses below the 200 GeV threshold of current ACTs. If dark matter annihilations proceed directly to neutrino-antineutrino pairs a substantial fraction of the time, IceCube will be competitive with gamma-ray telescopes for a much wider range of dark matter masses.Comment: 7 pages, 3 figures. v2: references added and minor revisions. v3: as published in PRD

High-Energy Neutrino Signatures of Dark Matter Decaying into Leptons

Decaying dark matter has previously been proposed as a possible explanation for the excess high energy cosmic ray electrons and positrons seen by PAMELA and the Fermi Gamma-Ray Space Telescope (FGST). To accommodate these signals however, the decays must be predominantly leptonic, to muons or taus, and therefore produce neutrinos, potentially detectable with the IceCube neutrino observatory. We find that, with five years of data, IceCube (supplemented by DeepCore) will be able to significantly constrain the relevant parameter space of decaying dark matter, and may even be capable of discovering dark matter decaying in the halo of the Milky Way.Comment: 4 pages, 1 figur

Are There Hints of Light Stops in Recent Higgs Search Results?

The recent discovery at the LHC by the CMS and ATLAS collaborations of the Higgs boson presents, at long last, direct probes of the mechanism for electroweak symmetry breaking. While it is clear from the observations that the new particle plays some role in this process, it is not yet apparent whether the couplings and widths of the observed particle match those predicted by the Standard Model. In this paper, we perform a global fit of the Higgs results from the LHC and Tevatron. While these results could be subject to as-yet-unknown systematics, we find that the data are significantly better fit by a Higgs with a suppressed width to gluon-gluon and an enhanced width to gamma gamma, relative to the predictions of the Standard Model. After considering a variety of new physics scenarios which could potenially modify these widths, we find that the most promising possibility is the addition of a new colored, charged particle, with a large coupling to the Higgs. Of particular interest is a light, and highly mixed, stop, which we show can provide the required alterations to the combination of gg and gamma gamma widths.Comment: 6 pages, 5 figure

Development of a Light-Weight, Reliable, Booster System for SHELS-Launched Payloads

Small satellite missions are often used to support low-cost space missions demonstrating new technologies. An economical source of low-cost space lift is to fly these satellites as secondary payloads aboard the Space Shuttle. The Shuttle has accommodations for flying these payloads using the Shuttle Hitchhiker Experiment Launch System (SHELS). While the relative costs for a Shuttle launch are at least an order of magnitude below the cost of a dedicated Expendable Launch Vehicle (ELV), final orbit altitude selection is limited to Shuttle mission goals. The Air Force Space Test Program (STP) is responsible for flying the Space Experiments Review Board (SERB) recommended experiments on a level-of-effort basis. Low-cost space lift is crucial to maximizing the number of SERB payloads that STP can support. Unfortunately, the typical Shuttle orbit does not provide a high enough orbit to guarantee the oneyear orbital lifetime required to meet STP mission objectives. A low-cost, autonomous STP Transfer Upper stage, Guided (TUG) that can boost an STP payload from a typical Shuttle orbit to a higher, longer duration orbit would allow STP to take advantage of the low-cost space lift provided by the Shuttle and still meet their mission requirements. The Air Force Research Laboratory Space Vehicles Directorate (AFRL/VS) is pursuing a solution to fulfill STP’s satellite lifting requirements by developing a low-cost, lightweight, reliable, strap-on propulsion module using several Small Business Innovative Research (SBIR) contracts focused on various parts of the TUG system. The Shuttle Expendable Rocket for Payload Augmentation (SHERPA) program will integrate all of these SBIR programs to meet the STP TUG requirement. The TUG system would be composed of several technologies being developed or already developed by AFRL/VS such as separation systems, guidance systems, propulsion modules, and modular bus architecture. The TUG would be re-startable for multiple orbit changes, station keeping, or deorbiting at the completion of a mission. Three versions of the TUG are envisioned. The first is a simple propulsion module that uses the satellite\u27s Attitude Control System (ACS) and Guidance, Navigation, and Control (GN&C) to provide stack guidance. The second is a fully autonomous TUG that lifts the payload to the higher orbit as cargo, separates from the payload, and then accomplishes a collision avoidance maneuver and propellant burn after payload separation. The third configuration is an autonomous TUG with a long duration module that allow experiments to use the TUG\u27s ACS, GN&C, and power systems in the intended final orbit. There are many challenges in the development of this vehicle. The most difficult of these is meeting the man-rating requirements of the Shuttle. All critical systems must have triple redundancy to ensure that the system does not threaten the Shuttle, its crew, or its mission. Another complication is producing a structure that meets the strict mass and volume restrictions of the SHELS system. Integration is als o a challenge, as many contractors and technologies are brought together under this program