| Dark Matter | ||
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One of the science goals of the Fermi is to probe the existence of Dark Matter. Dark Matter is an new type of matter which is non-luminous but affects its environment through gravity. The existence of such matter could e.g. explain the unexpected behaviour of the rotational curves in many galaxies.
In many theoretical extensions of the Standard Model of particles, there exists a stable and neutral Dark Matter particle known as a Weakly Interacting Massive Particle (WIMP). This particle is believed to be its own anti-particle, which means that two WIMPs will annihilate if they collide. The annihilations give many different types of particles, including photons that can be detected by the Fermi. Dark Matter would manifest itself in the Fermi as distorsions in the energy spectrum. The "smoking gun" for Dark Matter would be if a spectral line is seen. This would represent the annihilation of two WIMPs directly into two photons. Since WIMPs interact only by the gravitation force, the density of Dark Matter should be large in e.g. the Galactic Center. The Swedish the Fermi group studies how Dark Matter signals can be searched for with the Fermi and the various statistical challenges involved in such a search. |
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| High-Energy Emisson in Gamma-Ray Bursts | ||
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Gamma-Ray Bursts (GRBs) are the largest known explosions in the Universe. Due to their huge brightness we are able to detect them from very large distances, thereby viewing the very early Universe. The radiation processes and progenitor objects involved are still unclear.
We aim at determining the radiation and particle acceleration processes involved producing the GRBs. Detailed studies of the spectral and temporal data in the X- and gamma-ray band, as well as in-depth theoretical considerations of the photospheric emission and the non-thermal emission from other dissipation sites, is being performed. In particular, the GBM combined with the LAT instruments will give us a uniquely broad spectral range from 10 keV up to 100 GeV. Simulations of such observations show that we can expect to get a better understanding of the radiation processes of GRBs. A better understanding of the emission processes in GRBs will allows us to use them to study the early universe, as well as a "laboratory" to study plasmas under extreme conditions. Collaborators and the project: Asaf Pe'er, Yuki Kaneko, Vahe Petrosian, Peter Meszaros, Martin Rees, Chryssa Kouveliotou, Rob Preece, Attila Meszaros |
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| Beam Test | ||
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During the year 2006, the Fermi collaboration performed a series of tests at the CERN accelerator facility on a scaled down version of the main instrument on the Fermi, the Large Area Telescope (LAT). The scaled down instrument, known as the Calibration Unit (CU), consists of two full tower modules, each containing a tracker tower and a calorimeter module, and one additional calorimeter module. The purpose of the beam tests was to validate the Monte Carlo simulation software developed for the Fermi.
The tests were conducted at two different sites at CERN. The first test was done at the Proton Synchrotron (PS) facility, where the CU was exposed to beams of various particle types, such as photons, electrons, protons and pions, at energies ranging from 1 GeV to 10 GeV. The second test was performed at the Super Proton Synchrotron (SPS) facility, where higher energies were available. There the particles were electrons, protons and pions in the energy range 10-200 GeV. The Swedish Fermi group actively participated in both these tests and is now involved in the analysis of the data. The main interests are to study the direction and energy reconstructions, but also some specific studies related to calibration have been done. |
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