Vorträge, Kolloquien

17:00 Uhr KIP, INF 227, Otto-Haxel-Hörsaal
Prof. Guy D. Moore Institut für Kernphysik, TU Darmstadt

Could the Dark Matter be the QCD Axion?

First I will review the evidence that the Universe is full of dark matter, which outweighs ordinary neutron-proton-electron matter by a factor of 5. Then I will present a seemingly unrelated issue: the strong interactions respect time-reversal invariance, even though they could easily violate this symmetry a billion times more strongly. A hypothetical particle, the Axion, could explain both puzzles. I discuss the physics of the Axion in the early Universe, leading to a prediction for this particle's mass if it makes up the Dark Matter.

17:00 Uhr Neues Physikalisches Institut INF 226, Konferenzraum 1-3 (Room 00.101 bis 00.103)
Prof. Ronan McNulty University College Dublin (Ireland)

Central Exclusive Production at the LHC

17:00 Uhr Kirchhoff-Institut, INF 227 SR 1.403, SR 1.403
Prof. Dr. Michael Kues Hannoversches Zentrum für Optische Technologien

tba

16:30 Uhr Philosophenweg 12, großer Hörsaal
Frank Postberg Freie Universitaet Berlin

The subsurface ocean of Enceladus: A habitable place in our solar system

Saturn’s icy moon Enceladus harbours a global ocean, which lies under an ice crust of just a few kilometres thickness and above a rocky core. Through warm cracks in the crust a cryo-volcanic plume ejects ice grains and vapour into space providing access to materials originating from the ocean. The ocean is 30–55 km deep and provides an environment of mild salinity and alkaline pH. Hydrothermal activity is suspected to be occurring at the bottom of the ocean and also deep inside the water-percolated porous core. The energy is delivered by tidal dissipation. Two mass spectrometers aboard the Cassini spacecraft, the Cosmic Dust Analyzer (CDA) and the Ion and Neutral Gas Spectrometer (INMS) frequently carried out compositional in situ measurements of plume material emerging from the subsurface of Enceladus. Our latest results now show that, in addition to volatile organic compounds, some emitted ice grains contain concentrated macromolecular organic material with molecular masses clearly above 200u. Moreover, the mass spectra of the two instruments provide key constraints on the macromolecular structure. We suggest that the detected organic compounds and other materials found in the plume originate from Enceladus' hydrothermally active rocky core. Thermal ocean convection together with bubbles of volatile gases, transports these materials from the moon’s hydrothermal core up to the ocean surface. There, a spray of salty water together with droplets of solid organic nucleation cores - generated by bubble bursting and subsequently coated with ice from vapor freezing - are ejected into space.