Unresolved Unidentified Source Contribution to the Gamma-ray Background

The large majority of EGRET point sources remain without an identified low-energy counterpart, and a large fraction of these sources are most likely extragalactic. Whatever the nature of the extragalactic EGRET unidentified sources, faint unresolved objects of the same class must have a contribution to the diffuse extragalactic gamma-ray background (EGRB). Understanding this component of the EGRB, along with other guaranteed contributions from known sources, is essential if we are to use this emission to constrain exotic high-energy physics. Here, we follow an empirical approach to estimate whether a potential contribution of unidentified sources to the EGRB is likely to be important, and we find that it is. Additionally, we show how upcoming GLAST observations of EGRET unidentified sources, as well as of their fainter counterparts, can be combined with GLAST observations of the Galactic and extragalactic diffuse backgrounds to shed light on the nature of the EGRET unidentified sources even without any positional association of such sources with low-energy counterparts.Comment: 11 pages, 5 figures, submitted to Ap

Correction source contribution TI44

Currently, positron annihilation methods are the most effective methods of studying the defect structure of the substance. The radioisotopes are usually used as sources of positrons inmethods of positron annihilation. In this research, the contribution of Ti44 source in positron lifetime spectra is studied. The experiment was performed by positron lifetime spectrometry. As a result of this experiment the dependence of Ti44 source contribution on atomic number of studied element was obtained.This dependence was described by the function, obtained by the least squares method. This function can be used for Ti44 source contribution evaluation for any material

A statistical test of emission from unresolved point sources

We describe a simple test of the spatial uniformity of an ensemble of discrete events. Given an estimate for the point source luminosity function and an instrumental point spread function (PSF), a robust upper bound on the fractional point source contribution to a diffuse signal can be found. We verify with Monte Carlo tests that the statistic has advantages over the two-point correlation function for this purpose, and derive analytic estimates of the statistic's mean and variance as a function of the point source contribution. As a case study, we apply this statistic to recent gamma-ray data from the Fermi Large Area Telescope (LAT), and demonstrate that at energies above 10 GeV, the contribution of unresolved point sources to the diffuse emission is small in the region relevant for study of the WMAP Haze.Comment: 11 pages, 7 figures. Final version, accepted by Mon. Not. R. Astron. Soc. The definitive version is available at www.blackwell-synergy.com

Coherent Neutral Current Neutrino-Nucleus Scattering at a Spallation Source; a Valuable Experimental Probe

The coherent contribution of all neutrons in neutrino nucleus scattering due to the neutral current is examined considering the Spallation Neutron Source (SNS) as a source of neutrinos. SNS is a prolific pulsed source of electron and muon neutrinos as well as muon antineutrinos.Comment: 15 LaTex pages, 14 figures, 3 Table

Zero mode contribution in quarkonium correlators and in-medium properties of heavy quarks

We calculate the low energy contribution to quarkonium correlators in Euclidean time in lattice QCD. This contribution was found to give the dominant source of the temperature dependence of the correlators. We have found that the low energy contribution is well described by a quasi-particle model and have determined the effective temperature dependent heavy quark mass.Comment: Contribution to QM2008, 4 pages, LaTeX, uses iopart.cls, corrected typo

On the accuracy of the Adaptive Cross Approximation algorithm

This contribution identifies an often ignored source of uncertainty in the accuracy of the Adaptive Cross Approximation (ACA) algorithm.Postprint (published version

Improving meson two-point functions by low-mode averaging

Some meson correlation functions have a large contribution from the low lying eigenmodes of the Dirac operator. The contribution of these eigenmodes can be averaged over all positions of the source. This can improve the signal in these channels significantly. We test the method for meson two-point functions.Comment: Talk given at Lattice2004(spectrum), Fermilab, June 21-26, 200

Gather round the wiki-tree : virtual worlds as an open platform for architectural collaboration

The growth of internet based communication has facilitated the development of open source, collaborative projects. Here we describe the results of three 'Wikitecture' experiments in collaborative, open source architectural design within the virtual world Second Life. We describe the in-world platform developed and its use for a design competition entry. Issues such as contribution assessment and the role of open source collaborative design in architecture and construction are discussed, concluding with a wish list for future enhancements