The Institute for Gravitation and the Cosmos is a multidisciplinary institute of Penn State researchers dedicated to the study of the most fundamental structure and constituents of the Universe.
"In the search for dark matter, among the most interesting candidates is the neutralino, a neutral particle, predicted in supersymmetric extensions of the standard model, which interacts only weakly with other matter. Since the neutralino is expected to be stable, it may be possible to find particles that are relics of the early universe.
"Theorists have predicted that the sun's gravity can trap neutralinos, which could collect in its center and then annihilate each other. The standard-model particles created by these annihilations could subsequently decay, producing high-energy neutrinos that could escape from the sun and be detected on earth. Based on searches for these neutrinos, the IceCube Collaboration has now reported in Physical Review Letters new limits on neutralino annihilations in the sun.
"The IceCube neutrino detector is located between 1.5 and 2.5 km beneath the Antarctic ice, to reduce background events from cosmic rays. When muon neutrinos from the sun interact with the ice, they create relativistic charged particles (muons and showers of hadrons) that produce Cherenkov light, which is picked up by the detector. In an experiment lasting more than three months, no excess of neutrinos from the direction of the sun was detected. The experimentalists have therefore placed stringent limits on neutralino annihilations in the sun—a factor of 6 improvement over some previous limits - and from these, limits on the cross section for neutralino-proton interactions for neutralinos with masses above 250 GeV. These results narrow the possibilities for dark matter." (Stanley Brown, Physical Review Letters, from http://physics.aps.org/synopsis-for/10.1103/PhysRevLett.102.201302)
Penn State Prof. Stephane Coutu and graduate students Nick Conklin and Isaac Mognet were named in a NASA Group Achievement Award to the CREAM Science and Mission Support Team, in recognition of dedicated service and exemplary technical performance in support of the Cosmic Ray Energetics And Mass (CREAM) scientific balloon mission. The CREAM instrument was flown by high-altitude balloon in 2004/05, achieving a flight duration record of 42 days in three circumnavigations of the Antarctic continent. A modified version of the payload was flown again in 2005/06 for a further 28 days. A third version is planned to fly in late 2007. The CREAM mission measures high-energy cosmic nuclei at the limit of direct detectability, in an effort to elucidate the origin of these naturally occurring particles with energies in excess of those in the most powerful human-built particle accelerators today.