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terça-feira, novembro 01, 2011

One Step Closer to Dark Matter in Universe

ScienceDaily (Oct. 31, 2011) — Scientists all over the world are working feverishly to find the dark matter in the universe. Now researchers at Stockholm University have taken one step closer to solving the enigma with a new method.

The universe is still a mystery. We know what about 5 percent of the universe consists of. The rest is simply unknown. Researchers have gotten as far as knowing that a major portion, about 23 percent of the universe consists of a new kind of matter. No one has seen this matter, and no one knows what it consists of. The remaining roughly 72 percent of the universe is made up of something even more enigmatic, called dark energy. Jan Conrad and Maja Llena Garde are scientists at Fysikum, Stockholm University and the Oskar Klein Center for Cosmoparticle Physics, and they are part of the international research team that has taken a giant step toward finding dark matter with the help of a new method.

"With our new method, for the first time we have been able to exclude models regarded by many as the most natural ones. Previous attempts did not achieve the same sensitivity. What's more, our results are especially reliable," says Jan Conrad.

"We can't see dark matter because it doesn't interact with the matter we know about. Nor does it emit any light. It's virtually invisible. But we can determine that it affects the matter we're familiar with."

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Constraining dark matter models from a combined analysis of Milky Way satellites with the Fermi-LAT

The Fermi-LAT Collaboration: M. Ackermann et al (93 additional authors not shown)

(Submitted on 17 Aug 2011 (v1), last revised 19 Aug 2011 (this version, v2))

Satellite galaxies of the Milky Way are among the most promising targets for dark matter searches in gamma rays because of their large dynamical mass to light ratio and small expected background from astrophysical sources. We present a search for dark matter consisting of weakly interacting massive particles where we apply a joint likelihood analysis to 10 satellite galaxies with 24 months of data of the Fermi Large Area Telescope. No dark matter signal is detected. Taking into account the uncertainty in the dark matter distribution in the satellites, robust upper limits are placed on dark matter models. The 95% confidence level upper limits on the annihilation cross section range from about 1e-26 cm^3 s^-1 at 5 GeV to about 5e-23 cm^3 s^-1 at 1 TeV, depending on the dark matter annihilation final state. For the first time, using gamma rays, we are able to rule out models with the most generic cross section (~3e-26 cm^3 s^-1 for a purely s-wave cross section), without assuming additional astrophysical or particle physics boost factors.

Comments: 6 pages, 2 figures; Contact authors: Johann Cohen-Tanugi, Jan Conrad, and Maja Llena Garde

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Phenomenology (hep-ph)
Cite as: arXiv:1108.3546v2 [astro-ph.HE]

Submission historyFrom: Maja Llena Garde [view email
[v1] Wed, 17 Aug 2011 18:45:14 GMT (36kb,D)
[v2] Fri, 19 Aug 2011 09:08:04 GMT (40kb,D)