ACP Seminar (Astronomy - Cosmology - Particle Physics)

Speaker: Alexander Kusenko (UCLA)
Title: A tale of two spectra: from a gamma-ray puzzle to cosmic rays and dark matter
Date (JST): Thu, Apr 15, 2010, 13:00 - 14:30
Place: Seminar Room A
Related File: 245.pdf
Abstract: The seminar will discuss two unrelated phenomena.
(1) Both astrophysical and "new physics" solutions have been proposed to explain the apparent lack of absorption of TeV gamma rays on extragalactic background light (EBL). However, it appears that the gamma rays observed from distant blazars are not photons emitted at the source, but rather secondary photons produced in the interactions of cosmic rays with EBL. This interpretation opens new ways to learn about cosmic backgrounds, and, for the first time, to measure the magnetic fields in the voids.
(2) The first dedicated search for dark matter using X-ray telescopes (Suzaku and Chandra) has produced new limits on relic sterile neutrinos, and also reported a spectral feature consistent with a possible detection of a 5-keV dark-matter particle.
The mass and mixing are consistent with both dark matter and the pulsar kicks, but the evidence is statistically weak (2.8 sigma). The confirmation must await XXM-Newton observations later this year.
[Notice: The talk will be divided into two sessions (~ 40 mins. for each), with a 10 mins. break in between.]