Wednesday. I have a flat!!!! In a very nice area near Poppelsdorf!!!! A very well maintained apartment too!!! I don't have to look for a flat anymore!!!!
1110.3401
The directional DM detector
Vahsen, ...Yamaoka, et al
* TPC: consists of a gas-filled cylindrical chamber with multi-wire proportional chambers as end plates. Along its length, the chamber is divided into halves by means of a central high-voltage electrode disc, parallel to the electric field, in order to minimize the diffusion of the electrons coming from the ionization of the gas. A magnetic field is often applied along the length of the cylinder parallel to the electric field, in order to minimize the diffusion of the electrons coming from the ionization of the gas. On passing through the detector gas, a particle will produce primary ionization along its track. The z-coordinate (along the cylinder axis) is determined by measuring the drift time from the ionization event to the MWPC at the end. This is done using the usual technique of a drift chamber. The MWPC at the end is arranged with the anode wires in the azimuthal direction, theta, which provides information on the radial coordinate, r. To obtain the azimuthal direction, each cathode plane is divided into strips along the radial direction.
* GEM: Gaseous ionization detectors are able to collect electrons released by ionizing radiation, guiding them to a region with a large electric field, and thereby initiating an electron avalanche. The avalanche is able to produce enough electrons to create a current or charge large enough to be detected by electronics. GEMs create the large electric field in small holes in a thin polymer sheet; the avalanche occurs inside of these holes. The resulting electrons are ejected from the sheet, and a separate system must be used to collect the electrons and guide them to towards the readout.
Proceedings: Gas-filled Time Projection Chambers (TPCs) with Gas Electron Multipliers (GEMS) and pixels appear suitable for direction-sensitive WIMP dark matter searches. Present the BG and motivation for work in the technology, prototype work, and developement path towards and affordable 1-m^3-scale directional DM detector "dcube". Such detector particularly suitable for low-mass WIMP searches, and perhaps sufficiently sensitive to clearly determine whether the signals seen by DAMA, CoGeNT, and CRESST-II are due to low-mass WIMPs or background.
1110.3830
Ambiguous tests of GR on cosmological scales
Zuntz, Baker, Ferreira, Skordis
Argue that any Parameterized Post-Friedman (PPF) approach should always be accompanied by a characterization of the class of modified gravity models it is seeking to approximate.
1110.3979
Systematics in lensing reconstruction: Dark matter rings in the sky?
Ponente, Diego
Non-parametric lensing methods: useful way of reconstructing the lensing mass of a cluster without making assumptions about the way the mass is distributed in the cluster. Advantage: interesting when studying non-relaxed dynamical states. Limitations, implications studied with the "DM ring" cluster CL0024+17. Mock cluster of known radial profile, obtain map for the arcs (theta map) [arcs?]. Also calculate shear field associated with the mock cluster. Combine positions of the arcs and the two-direction shear [what?], perform inversion of the lens equation (biconjugate gradient & quadratic programming) to reconstruct the convergence map of the mock cluster. Explore solution space of convergence map; compare radial density profiles to the density profile of the mock cluster. When exact solutions are forced for the inversion matrix, systematic effects resembling ring structures encountered that clearly depart from the original convergence map. Overfitting lensing data with a non-parameteric method can produce ring-like structures similar to the alleged one in CL0024.
* Owww, James Jee's cluster...
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