33 results match your criteria: "The Oskar Klein Centre for Cosmoparticle Physics[Affiliation]"

Measurement of the high-energy gamma-ray emission from the Moon with the Fermi Large Area Telescope.

Phys Rev D

April 2016

Istituto Nazionale di Fisica Nucleare, Sezione di Milano, I-20133 Milano, Italy.

We have measured the gamma-ray emission spectrum of the Moon using the data collected by the Large Area Telescope onboard the Fermi satellite during its first seven years of operation, in the energy range from 30 MeV up to a few GeV. We have also studied the time evolution of the flux, finding a correlation with the solar activity. We have developed a full Monte Carlo simulation describing the interactions of cosmic rays with the lunar surface.

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The dwarf spheroidal satellite galaxies (dSphs) of the Milky Way are some of the most dark matter (DM) dominated objects known. We report on γ-ray observations of Milky Way dSphs based on six years of Fermi Large Area Telescope data processed with the new Pass8 event-level analysis. None of the dSphs are significantly detected in γ rays, and we present upper limits on the DM annihilation cross section from a combined analysis of 15 dSphs.

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In this work we present results of a direct search for strange quark matter (SQM) in cosmic rays with the PAMELA space spectrometer. If this state of matter exists it may be present in cosmic rays as particles, called strangelets, having a high density and an anomalously high mass-to-charge (A/Z) ratio. A direct search in space is complementary to those from ground-based spectrometers.

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Inferred cosmic-ray spectrum from Fermi large area telescope γ-ray observations of Earth's limb.

Phys Rev Lett

April 2014

Department of Physics, Stockholm University, AlbaNova, SE-106 91 Stockholm, Sweden and The Oskar Klein Centre for Cosmoparticle Physics, AlbaNova, SE-106 91 Stockholm, Sweden.

Article Synopsis
  • Recent measurements from ATIC-2, CREAM, and PAMELA have revealed unexpected patterns in cosmic-ray proton and helium spectra, showing hardening above several hundred GeV and a gradual softening below this range.
  • The findings suggest a harder spectrum for helium compared to protons, which may provide insights into the origins of high-energy cosmic rays.
  • Analysis using Fermi Large Area Telescope data indicates that both single and broken power law models fit the local proton spectrum well, with indices around 2.68 and 2.61 for energies above 200 GeV.
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Observations of occultations of bright -ray sources by the Sun may reveal predicted pair halos around blazars andor new physics, such as, e.g., hypothetical light dark matter particles-axions.

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New limits on dark matter annihilation from Alpha Magnetic Spectrometer cosmic ray positron data.

Phys Rev Lett

October 2013

The Oskar Klein Centre for Cosmoparticle Physics, Department of Physics, Stockholm University, AlbaNova, SE-106 91 Stockholm, Sweden.

The Alpha Magnetic Spectrometer experiment onboard the International Space Station has recently provided cosmic ray electron and positron data with unprecedented precision in the range from 0.5 to 350 GeV. The observed rise in the positron fraction at energies above 10 GeV remains unexplained, with proposed solutions ranging from local pulsars to TeV-scale dark matter.

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Gamma rays from dark matter annihilations strongly constrain the substructure in halos.

Phys Rev Lett

October 2009

The Oskar Klein Centre for Cosmoparticle Physics, Department of Physics, Stockholm University, AlbaNova University Center, SE - 106 91 Stockholm, Sweden.

To fit recent data, e(+/-) from dark matter (DM) needs a boosted annihilation rate. This may imply an observable level of gamma rays from nearby galaxy clusters for the Fermi satellite. Using EGRET data, we limit the minimum mass of DM substructures to be about 5x10(3) times larger than for cold DM, meaning a cutoff similar to, e.

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Dark matter interpretation of recent electron and positron data.

Phys Rev Lett

July 2009

The Oskar Klein Centre for Cosmoparticle Physics, Department of Physics, Stockholm University, AlbaNova, SE-106 91 Stockholm, Sweden.

We analyze the recently released Fermi-LAT data on the sum of electrons and positrons. Compared to a conventional, pre-Fermi, background model, a surprising excess in the several hundred GeV range is found and here we analyze it in terms of dark matter models. We also compare with newly published results from PAMELA and H.

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