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

Towards low-latency real-time detection of gravitational waves from compact binary coalescences in the era of advanced detectors

Electromagnetic (EM) follow-up observations of gravitational wave (GW) events will help shed light on the nature of the sources, and more can be learned if the EM follow-ups can start as soon as the GW event becomes observable. In this paper, we propose a computationally efficient time-domain algorithm capable of detecting gravitational waves (GWs) from coalescing binaries of compact objects with nearly zero time delay. In case when the signal is strong enough, our algorithm also has the flexibility to trigger EM observation before the merger. The key to the efficiency of our algorithm arises from the use of chains of so-called Infinite Impulse Response (IIR) filters, which filter time-series data recursively. Computational cost is further reduced by a template interpolation technique that requires filtering to be done only for a much coarser template bank than otherwise required to sufficiently recover optimal signal-to-noise ratio. Towards future detectors with sensitivity extending to lower frequencies, our algorithm's computational cost is shown to increase rather insignificantly compared to the conventional time-domain correlation method. Moreover, at latencies of less than hundreds to thousands of seconds, this method is expected to be computationally more efficient than the straightforward frequency-domain method.Comment: 19 pages, 6 figures, for PR

Payload/orbiter contamination control requirement study, volume 2, exhibit A

The computer printout data generated during the Payload/Orbiter Contamination Control Requirement Study are presented. The computer listings of the input surface data matrices, the viewfactor data matrices, and the geometric relationship data matrices for the three orbiter/spacelab configurations analyzed in this study are given. These configurations have been broken up into the geometrical surfaces and nodes necessary to define the principal critical surfaces whether they are contaminant sources, experimental surfaces, or operational surfaces. A numbering scheme was established based upon nodal numbers that relates the various spacelab surfaces to a specific surface material or function. This numbering system was developed for the spacelab configurations such that future extension to a surface mapping capability could be developed as required

No Indications of Axion-Like Particles From Fermi

As very high energy (~100 GeV) gamma rays travel over cosmological distances, their flux is attenuated through interactions with the extragalactic background light. Observations of distant gamma ray sources at energies between ~200 GeV and a few TeV by ground-based gamma ray telescopes such as HESS, however, suggest that the universe is more transparent to very high energy photons than had been anticipated. One possible explanation for this is the existence of axion-like-particles (ALPs) which gamma rays can efficiently oscillate into, enabling them to travel cosmological distances without attenuation. In this article, we use data from the Fermi Gamma Ray Space Telescope to calculate the spectra at 1-100 GeV of two gamma ray sources, 1ES1101-232 at redshift z=0.186 and H2356-309 at z=0.165, and use this in conjunction with the measurements of ground-based telescopes to test the ALP hypothesis. We find that the observations can be well-fit by an intrinsic power-law source spectrum with indices of -1.72 and -2.1 for 1ES1101-232 and H2356-309, respectively, and that no ALPs or other exotic physics is necessary to explain the observed degree of attenuation.Comment: 7 pages, 4 figures. v3: Matches published version, the analysis of H2356-309 is revised, no change in conclusion

Summed Parallel Infinite Impulse Response (SPIIR) Filters For Low-Latency Gravitational Wave Detection

With the upgrade of current gravitational wave detectors, the first detection of gravitational wave signals is expected to occur in the next decade. Low-latency gravitational wave triggers will be necessary to make fast follow-up electromagnetic observations of events related to their source, e.g., prompt optical emission associated with short gamma-ray bursts. In this paper we present a new time-domain low-latency algorithm for identifying the presence of gravitational waves produced by compact binary coalescence events in noisy detector data. Our method calculates the signal to noise ratio from the summation of a bank of parallel infinite impulse response (IIR) filters. We show that our summed parallel infinite impulse response (SPIIR) method can retrieve the signal to noise ratio to greater than 99% of that produced from the optimal matched filter. We emphasise the benefits of the SPIIR method for advanced detectors, which will require larger template banks.Comment: 9 pages, 6 figures, for PR

Searching for Dark Matter with Future Cosmic Positron Experiments

Dark matter particles annihilating in the Galactic halo can provide a flux of positrons potentially observable in upcoming experiments, such as PAMELA and AMS-02. We discuss the spectral features which may be associated with dark matter annihilation in the positron spectrum and assess the prospects for observing such features in future experiments. Although we focus on some specific dark matter candidates, neutralinos and Kaluza-Klein states, we carry out our study in a model independent fashion. We also revisit the positron spectrum observed by HEAT.Comment: 19 pages, 33 figure

Survival of drug resistant tuberculosis patients in Lithuania: retrospective national cohort study

The research leading to these results has received funding from the European Community's Seventh Framework Programme (FP7/2007-2013) under grant agreement FP7-223681.

Elastic Scattering and Direct Detection of Kaluza-Klein Dark Matter

Recently a new dark matter candidate has been proposed as a consequence of universal compact extra dimensions. It was found that to account for cosmological observations, the masses of the first Kaluza-Klein modes (and thus the approximate size of the extra dimension) should be in the range 600-1200 GeV when the lightest Kaluza-Klein particle (LKP) corresponds to the hypercharge boson and in the range 1 - 1.8 TeV when it corresponds to a neutrino. In this article, we compute the elastic scattering cross sections between Kaluza-Klein dark matter and nuclei both when the lightest Kaluza-Klein particle is a KK mode of a weak gauge boson, and when it is a neutrino. We include nuclear form factor effects which are important to take into account due to the large LKP masses favored by estimates of the relic density. We present both differential and integrated rates for present and proposed Germanium, NaI and Xenon detectors. Observable rates at current detectors are typically less than one event per year, but the next generation of detectors can probe a significant fraction of the relevant parameter space.Comment: 23 pages, 11 figures; v2,v3: Ref. added, discussion improved, conclusions unchanged. v4: Introduction was expanded to be more appropriate for non experts. Various clarifications added in the text. Version to be published in New Journal of Physic

The Higgs Sector and CoGeNT/DAMA-Like Dark Matter in Supersymmetric Models

Recent data from CoGeNT and DAMA are roughly consistent with a very light dark matter particle with m\sim 4-10\gev and spin-independent cross section of order \sigma_{SI} \sim (1-3)\times 10^{-4}\pb. An important question is whether these observations are compatible with supersymmetric models obeying $\Omega h^2\sim 0.11$ without violating existing collider constraints and precision measurements. In this talk, I review the fact the the Minimal Supersymmetric Model allows insufficient flexibility to achieve such compatibility, basically because of the highly constrained nature of the MSSM Higgs sector in relation to LEP limits on Higgs bosons. I then outline the manner in which the more flexible Higgs sectors of the Next-to-Minimal Supersymmetric Model and an Extended Next-to-Minimal Supersymmetric Model allow large $\sigma_{SI}$ and $\Omega h^2\sim 0.11$ at low LSP mass without violating LEP, Tevatron, BaBar and other experimental limits. The relationship of the required Higgs sectors to the NMSSM "ideal-Higgs" scenarios is discussed.Comment: 11 pages, 3 figures. To appear in Proceedings of PASCOS 2010. The paper is a compilation of talks given at: PASCOS 2010, ORSAY Workshop on "Higgs Hunting", and SLAC Workshop on "Topologies for Early LHC Searches

Ultra High Energy Cosmic Rays: The disappointing model

We develop a model for explaining the data of Pierre Auger Observatory (Auger) for Ultra High Energy Cosmic Rays (UHECR), in particular, the mass composition being steadily heavier with increasing energy from 3 EeV to 35 EeV. The model is based on the proton-dominated composition in the energy range (1 - 3) EeV observed in both Auger and HiRes experiments. Assuming extragalactic origin of this component, we argue that it must disappear at higher energies due to a low maximum energy of acceleration, E_p^{\max} \sim (4 - 10) EeV. Under an assumption of rigidity acceleration mechanism, the maximum acceleration energy for a nucleus with the charge number Z is ZE_p^{\max}, and the highest energy in the spectrum, reached by Iron, does not exceed (100 - 200) EeV. The growth of atomic weight with energy, observed in Auger, is provided by the rigidity mechanism of acceleration, since at each energy E=ZE_p^{\max} the contribution of nuclei with Z' < Z vanishes. The described model has disappointing consequences for future observations in UHECR: Since average energies per nucleon for all nuclei are less than (2 - 4) EeV, (i) pion photo-production on CMB photons in extragalactic space is absent; (ii) GZK cutoff in the spectrum does not exist; (iii) cosmogenic neutrinos produced on CMBR are absent; (iv) fluxes of cosmogenic neutrinos produced on infrared - optical background radiation are too low for registration by existing detectors and projects. Due to nuclei deflection in galactic magnetic fields, the correlation with nearby sources is absent even at highest energies.Comment: Essentially revised version as published in Astropart. Physics 10 pages, 6 figure