DAMA’s 10-Year Fascination With Dark Matter
Simulated dark matter halo from a cosmological N-body simulation.
What does the physicists from the University of Rome “Tor Vergata”, the University of Rome “La Sapienza”, the Italian National Institute for Nuclear Physics and the Institute of High Energy Physics in Beijing, China all have in common? Under the Gran Sasso Mountain in Central Italy this group, under the name of DAMA (DArk MAtter), claims to have observed dark matter. And if this find is true, has possibly come the deepest truth of cosmology and particle-physics that everyone has ever searched for, a search which has been going on for ten years regardless of what critics have said.
Physicsworld.com refers to the extreme controversy going on regarding DAMA, a group of dark-matter hunters in Italy, and their critics who are unconvinced of the group’s claims of finding the “first ever direct observation of dark-matter particles.” DAMA has an operation 1400 m beneath the Gran Sasso mountain in Central Italy consisting of a sodium-iodide detector, with their latest claim saying they have ” observed a seasonal variation in the signal from the detector caused by dark-matter particles interacting with the sodium iodide.”
The signal they are referring to is “a sinusoidal modulation that peaks in early June and goes through a minimum in early December — a signature that the group interprets as being caused by the Earth’s motion through the “halo” of dark matter that surrounds the Milky Way.” How they rationalize this is that the Earth travels through an assumed static halo, at the same time the sun orbits around the galactic center. We know that the Sun travels with Earth in June, against it in December, with the velocity relative to the dark-matter halo at a maximum and minimum at these said times.
DAMA says that this variation should then manifest itself as an annual variation in the rate of dark-matter particles, passing through their DAMA detector—a dark-matter wind. With its original claim made in 1998 from an experiment called DAMA/Nal, using 100 kg of detecting material, this very same claim was made in 200 and 2003 but with more collected data. What is exciting is that this year in the April Venice conference is they announced data from the past four-years, showing results from their upgraded DAMA/LIBRA, which refers to their Large Sodium Iodide Bulk for Rare Processes experiment.
Between the two experiments, they claim that ” “the presence of dark-matter particles in the galactic halo is supported at a confidence level of 8.2 standard deviations”, which equates to a chance of less than one in 4 × 1015 that the result is a statistical fluke (arXiv:0804.2741; accepted for publication in European Physical Journal C).”
DAMA has been the pioneer most active in the direct investigation of Dark Matter particles in the galactic halo—the galactic spheroid, the galactic corona, and the dark matter halo—used to describe a galaxy’s extended and rough spherical component. This extends beyond the main visible component, with the distinction of the halo and main galaxy’s body most noticeable in spiral galaxies. This is when the spherical shape contrasts with the flat disc, as compared to the lack of a sharp transition in the elliptical galaxy between the body of the galaxy and the halo.
This entry was posted on Wednesday, July 30th, 2008 at 8:39 pm and is filed under Space Agency News. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.
