We present a complete calculation of the cross section for neutralino annihilation into the two-gluon final state. This channel can be quite important for the phenomenology of neutralino annihilation due to the well-known helicity suppression of neutralino annihilation into light quarks and leptons. In addition, we calculate the cross section for annihilation of neutralinos into a gluon and qua...

Recent claims of a line in the Fermi-LAT photon spectrum at 130 GeV are suggestive of dark matter annihilation in the galactic center and other dark matter-dominated regions. If the Fermi feature is indeed due to dark matter annihilation, the best-fit line cross-section, together with the lack of any corresponding excess in continuum photons, poses an interesting puzzle for models of thermal da...

Positron annihilation was applied to measuring critical pore sizes in various materials. In recent years, positron annihilation with a variable-energy positron beam has emerged as a powerful tool for the investigation of porous thin films synthesized as low-k dielectrics, high performance gas sensor materials, and so on. This paper is a brief overview of recent progress in nanopore characteriza...

A problem to account for the direct electron-positron annihilation in positron-hydrogen scattering above the positronium formation threshold has been resolved within the time independent formalism. The generalization of the optical theorem is derived for the case when an absorption potential is present in the Hamiltonian. With this theorem the annihilation cross section is fully determined by s...

In this article‎, ‎a new scheme inspired from collocation method is‎ ‎presented for numerical solution of stiff initial-value problems and Fredholm integral equations of the first kind based on the derivatives of residual function‎. ‎Then‎, ‎the error analysis‎ ‎of this method is investigated by presenting an error bound‎. ‎Numerical comparisons indicate that the‎ ‎presented method yields accur...

Measurements of positron-on-molecule annihilation have established that positrons attach to a variety of molecules via vibrational Feshbach resonances VFRs . These resonances, in turn, result in greatly enhanced positron annihilation rates beyond those expected in simple collisions. A recent paper J. A. Young and C. M. Surko, Phys. Rev. Lett. 99, 133201 2007 described experimental studies and a...

We study the effects of dark matter annihilation during and after the cosmic recombination epoch on the cosmic microwave background anisotropy, taking into account the detailed energy deposition of the annihilation products. It is found that a fairly stringent constraint on the annihilation cross section is imposed for TeV scale dark matter masses from WMAP observations.

This article presents an overview of current understanding of the interaction of low-energy positrons with molecules with emphasis on resonances, positron attachment, and annihilation. Measurements of annihilation rates resolved as a function of positron energy reveal the presence of vibrational Feshbach resonances VFRs for many polyatomic molecules. These resonances lead to strong enhancement ...

Assuming that the enhanced MeV emission from the MeV blazar PKS 0208{ 512 observed by COMPTEL on occasions is due to annihilation in a pair plasma, we estimate parameters of the annihilation region: its size, the number density of particles, and the variability timescale. The values we nd are in accord with our present-dayknowledge of emission mechanisms operating in AGN. The constructed model ...

The electron-positron annihilation spectrum observed by SPI/INTEGRAL during deep Galactic Center region exposure is reported. The line energy (510.954±0.075 keV) is consistent with the unshifted annihilation line. The width of the annihilation line is 2.37±0.25 keV (FWHM), while the strength of the ortho-positronium continuum suggests that the dominant fraction of positrons (94±6%) form positro...