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Using data collected at the Pierre Auger Observatory during the past 3.7 years, we demonstrated a correlation between the arrival directions of cosmic rays with energy above 6 x 10(19) electron volts and the positions of active galactic nuclei (AGN) lying within approximately 75 megaparsecs. We rejected the hypothesis of an isotropic distribution of these(More)
We describe a scalable parallelization of Geant4 using commodity hardware in a collab-orative effort between the College of Computer Science and the Department of Physics at Northeastern University. The system consists of a Beowulf cluster of 32 Pentium II processors with 128 MBytes of memory each, connected via ATM and fast Ethernet. The bulk of the(More)
In this work we reexamine the opacity of the cosmic background radiation to the propagation of extremely high energy cosmic rays. We use the continuous energy loss approximation to provide spectral modification factors for several hypothesized cosmic ray sources. Earlier problems with this approximation are resolved including the effects of resonances other(More)
The last phase of leaf development, generally referred to as leaf senescence, is an integral part of plant development that involves massive programmed cell death. Due to a sharp decline of photosynthetic capacity in a leaf, senescence limits crop yield and forest plant biomass production. However, the biochemical components and regulatory mechanisms(More)
A water bridge refers to an experimental "flexible cable" made up of pure de-ionized water, which can hang across two supports maintained with a sufficiently large voltage difference. The resulting electric fields within the de-ionized water flexible cable maintain a tension that sustains the water against the downward force of gravity. A detailed(More)
The surface detector array of the Pierre Auger Observatory is sensitive to Earth-skimming tau neutrinos that interact in Earth's crust. Tau leptons from nu(tau) charged-current interactions can emerge and decay in the atmosphere to produce a nearly horizontal shower with a significant electromagnetic component. The data collected between 1 January 2004 and(More)
MoEDAL is designed to identify new physics in the form of long-lived highly ionizing particles produced in high-energy LHC collisions. Its arrays of plastic nuclear-track detectors and aluminium trapping volumes provide two independent passive detection techniques. We present here the results of a first search for magnetic monopole production in 13 TeV(More)
The energy spectrum of cosmic rays above 2.5 x 10;{18} eV, derived from 20,000 events recorded at the Pierre Auger Observatory, is described. The spectral index gamma of the particle flux, J proportional, variantE;{-gamma}, at energies between 4 x 10;{18} eV and 4 x 10;{19} eV is 2.69+/-0.02(stat)+/-0.06(syst), steepening to 4.2+/-0.4(stat)+/-0.06(syst) at(More)
Results on the radiation hardness of photodiodes to fast neutrons are presented. Four photodiodes (three avalanche photodiodes from two manufacturers, and one PIN photodiode) were exposed to neutrons from a Cf source at Oak Ridge National Laboratory. The e!ects of this radiation on many parameters such as gain, intrinsic dark current, quantum e$ciency,(More)