40898720
A fast embedded system for radio detection of cosmic rays
For the detection of radio signals from ultra high energy (> 1017 eV) cosmic rays in the frequency range up to 80 MHz an embedded system was designed, built, and tested. A steep band-pass filter in the range of 30 to 80 MHz suppresses the main source of radio frequency interferences. To fulfill the data acquisition (DAQ) task, four 180 MHz twelve bit ADCs have to be read-out by a FPGA into a two gigabyte buffer memory. Furthermore the FPGA contains the trigger and a Altera NIOS II soft-core processor for data management. A GPS receiver controls the timing of the system. For the read-out an Ethernet-link and a CAN interface to a WLAN communication board is foreseen. The architecture of the system and the measured performance of the DAQ-board are described.
125135710
THE FREJUS NUCLEON DECAY EXPERIMENT
123338629
IceCube: A Multipurpose Neutrino Telescope
IceCube is a new high-energy neutrino telescope which will be coming online in the near future. IceCube will be capable of measuring fluxes of all three flavors of neutrino, and its peak neutrino energy sensitivity will be in the TeV–PeV range. Here, after a brief description of the detector, we describe its anticipated performance with a selection of physics topics: supernovae, extraterrestrial diffuse and point sources of neutrinos, gamma-ray bursts, neutrinos from WIMP annihilation, and cosmic ray composition.
210155517
The IceCube Neutrino Observatory VI: Neutrino Oscillations, Supernova Searches, Ice Properties
IceCube DeepCore can study atmospheric neutrino oscillations through a combination of its low energy reach, as low as about 10 GeV, and its unprecedented statistical sample, of about 150,000 triggered atmospheric muon neutrinos per year. With the diameter of the earth as a baseline, the muon neutrino disappearance minimum and tau neutrino appearance maximum are expected at about 25 GeV, which is considerably lower energy than typical IceCube neutrino events, but higher than the energies at which accelerator-based experiments have detected oscillations. νμ disappearance and ντ appearance from neutrino oscillation can be measured in IceCube DeepCore. We present here the status of the newly developed low energy reconstruction algorithms, the expected experimental signatures, and the proposed approach for such neutrino oscillation measurements. Corresponding authors: Sebastian Euler (seuler@icecube.wisc.edu), Laura Gladstone(gladstone@icecube.wisc.edu), Jason Koskinen(koskinen@psu.edu), Donglian Xu(dxu@crimson.ua.edu) III. Physikalisches Institut, RWTH Aachen University, D-52056 Aachen, Germany Dept. of Physics, University of Wisconsin, Madison, WI 53706, USA Dept. of Physics, Pennsylvania State University, University Park, PA 16802, USA Dept. of Physics and Astronomy, University of Alabama, Tuscaloosa, AL 35487, USA
1694798
Design and performance of the lead-concrete geiger tower array within the HEGRA experiment
Abstract The HEGRA experiment is a hybrid installation characterized by four different types of detectors (scintillator counters, open Cherenkov counters, Cherenkov telescopes and Geiger towers) located within one detector array. The Geiger towers are built with the objective to measure the local energy deposition and to reconstruct and identify muon tracks. In addition each tower may serve as an independent high resolution muon flux monitor. With these properties the Geiger towers are operating as geometric and energetic calibration instruments for the other detector components and as additional independent measurement instruments with respect to the γ-hadron separation and the measurement of the chemical composition. In this paper the design, the performance, and the basic principles of the data analysis of the lead-concrete Geiger towers are described.
2219103
AMANDA - first running experiment to use GRID in production
The Grid technologies are in ongoing development. Using current Grid toolkits like the Globus toolkit gives one the possibility to build up virtual organizations. Although these tookits are in still under development and do not feature all functionality, they can already now be used to set up an efficient computing environment for physics collaborations with only moderate work. We discuss in this paper the use of such a computing structure in two running experiments - the AMANDA (AMANDA = Antarctic muon and neutrino detector array) neutrino telescope and the D0 experiment at Tevatron, Fermilab. One of the main features of our approach is to avoid reprogramming of the existing software which is based on several programming languages (FORTRAN, C/C++, JAVA). This was realized with software layers around the collaboration software taking care about in- and output, user notification, tracking of running jobs, etc. A further important aspect is the resolution of library dependencies, which occur when a user runs self-compiled jobs on machines, where these libraries are not installed. These dependencies are also resolved with this layers.
14043557
Fivebranes, membranes and non-perturbative string theory
Abstract Non-perturbative instanton corrections to the moduli space geometry of type IIA string theory compactified on a Calabi-Yau space are derived and found to contain order e −1/ g s contributions, where g s is the string coupling. The computation reduces to a weighted sum of supersymmetric extremal maps of strings, membranes and fivebranes into the Calabi-Yau space, all three of which enter on equal footing. It is shown that a supersymmetric 3-cycle is one for which the pullback of the Kahler form vanishes and the pullback of the holomorphic three-form is a constant multiple of the volume element. Quantum mirror symmetry relates the sum in the IIA theory over supersymmetric, odd-dimensional cycles in the Calabi-Yau space to a sum in the IIB theory over supersymmetric, even-dimensional cycles in the mirror.
119274731
Four-derivative brane couplings from string amplitudes
A bstractWe evaluate the string theory disc amplitude of one Ramond-Ramond field C(p−3) and two Neveu-Schwarz B-fields in the presence of a single Dp-brane in type II string theory. From this amplitude we extract the four-derivative (or equivalently order α′2) part of the Dp-brane action involving these fields. We show that the new couplings are invariant under R-R and NS-NS gauge transformations and compatible with linear T-duality.
119443409
Strings, black holes and conformal field theory
The SL(2,R)/U(1) gauged Wess-Zumino-Witten model is an exact conformal field theory describing a black hole in two-dimensional space-time. The free field approach of Bershadsky and Kutasov is a suitable formulation of this CFT in order to compute physically interesting quantities of this black hole. We find the space-time interpretation of this model for k=9/4 and show that it reproduces the metric and the dilaton found by Dijkgraaf, E. Verlinde and H. Verlinde in the mini-superspace approximation. We compute the two- and three-point functions of tachyons interacting in the black hole background and analyse in detail the form of the four-point tachyon scattering amplitude. We discuss the connection to the c=1 matrix model and the deformed matrix model of Jevicki and Yoneya.
10027781
SUPERSYMMETRIC CYCLES IN EXCEPTIONAL HOLONOMY MANIFOLDS AND CALABI-YAU FOUR-FOLDS
We derive in the SCFT and low energy effective action frameworks the necessary and sufficient conditions for supersymmetric cycles in exceptional holonomy manifolds and Calabi-Yau four-folds. We show that the Cayley cycles in Spin(7) holonomy eight-manifolds and the associative and coassociative cycles in G2 holonomy seven-manifolds preserve half of the space-time supersymmetry. We find that while the holomorphic and special Lagrangian cycles in Calabi-Yau four-folds preserve half of the space-time supersymmetry, the Cayley submanifolds are novel as they preserve only one quarter of it. We present some simple examples. Finally, we discuss the implications of these supersymmetric cycles on mirror symmetry in higher dimensions.
4411256
Discovery of radio emission from the brown dwarf LP944-20
Brown dwarfs are not massive enough to sustain thermonuclear fusion of hydrogen at their centres, but are distinguished from gas-giant planets by their ability to burn deuterium. Brown dwarfs older than ∼10 Myr are expected to possess short-lived magnetic fields and to emit radio and X-rays only very weakly from their coronae. An X-ray flare was recently detected on the brown dwarf LP944-20, whereas previous searches for optical activity (and one X-ray search) yielded negative results. Here we report the discovery of quiescent and flaring radio emission from LP944-20, with luminosities several orders of magnitude larger than predicted by the empirical relation between the X-ray and radio luminosities that has been found for many types of stars. Interpreting the radio data within the context of synchrotron emission, we show that LP944-20 has an unusually weak magnetic field in comparison to active M-dwarf stars, which might explain the previous null optical and X-ray results, as well as the strength of the radio emissions compared to those at X-ray wavelengths.