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K. D. de Vries

Publications and source records attributed to K. D. de Vries.

262 records · Page 15Linked to original sources
arXiv2013

Search for time-independent neutrino emission from astrophysical sources with 3 years of IceCube data

We present the results of a search for neutrino point sources using the IceCube data collected between April 2008 and May 2011 with three partially completed configurations of the detector: the 40-, 59- and 79-string configurations. The live-time of this data set are 1,040 days. An unbinned maximum likelihood ratio test was used to search for an excess of neutrinos above the atmospheric background at any given direction in the sky. By adding two more years of data with improved event selection and reconstruction techniques, the sensitivity was improved by a factor 3.5 or more with respect to the previously published results obtained with the 40-string configuration of IceCube. We performed an all-sky survey and a dedicated search using a catalog of \textit{a priori} selected objects observed by other telescopes. In both searches, the data are compatible with the background-only hypothesis. In the absence of evidence for a signal, we set upper limits on the flux of muon neutrinos. For an E$^{-2}$ neutrino spectrum, the observed limits are between 0.9 and $23.2\times 10^{-12}$ TeV$^{-1}$ cm$^{-2}$s$^{-1}$. We also report upper limits for neutrino emission from groups of sources which were selected according to theoretical models or observational parameters and analysed with a stacking approach.

astro-ph.HE↗
arXiv2011

Coherent Cherenkov Radiation from Cosmic-Ray-Induced Air Showers

Very energetic cosmic rays entering the atmosphere of the Earth will create a plasma cloud moving with almost the speed of light. The magnetic field of the Earth induces an electric current in this cloud which is responsible for the emission of coherent electromagnetic radiation. We propose to search for a new effect: due to the index of refraction of air this radiation is collimated in a Cherenkov cone. To express the difference from usual Cherenkov radiation, i.e. the emission from a fast moving electric charge, we call this magnetically-induced Cherenkov radiation. We indicate its signature and possible experimental verification.

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arXiv2011

Search for First Harmonic Modulation in the Right Ascension Distribution of Cosmic Rays Detected at the Pierre Auger Observatory

We present the results of searches for dipolar-type anisotropies in different energy ranges above $2.5\times 10^{17}$ eV with the surface detector array of the Pierre Auger Observatory, reporting on both the phase and the amplitude measurements of the first harmonic modulation in the right-ascension distribution. Upper limits on the amplitudes are obtained, which provide the most stringent bounds at present, being below 2% at 99% $C.L.$ for EeV energies. We also compare our results to those of previous experiments as well as with some theoretical expectations.

astro-ph.HE↗
arXiv2011

Advanced functionality for radio analysis in the Offline software framework of the Pierre Auger Observatory

The advent of the Auger Engineering Radio Array (AERA) necessitates the development of a powerful framework for the analysis of radio measurements of cosmic ray air showers. As AERA performs "radio-hybrid" measurements of air shower radio emission in coincidence with the surface particle detectors and fluorescence telescopes of the Pierre Auger Observatory, the radio analysis functionality had to be incorporated in the existing hybrid analysis solutions for fluoresence and surface detector data. This goal has been achieved in a natural way by extending the existing Auger Offline software framework with radio functionality. In this article, we lay out the design, highlights and features of the radio extension implemented in the Auger Offline framework. Its functionality has achieved a high degree of sophistication and offers advanced features such as vectorial reconstruction of the electric field, advanced signal processing algorithms, a transparent and efficient handling of FFTs, a very detailed simulation of detector effects, and the read-in of multiple data formats including data from various radio simulation codes. The source code of this radio functionality can be made available to interested parties on request.

astro-ph.IM↗
arXiv2010

A new limit on the Ultra-High-Energy Cosmic-Ray flux with the Westerbork Synthesis Radio Telescope

A particle cascade (shower) in a dielectric, for example as initiated by an ultra-high energy cosmic ray, will have an excess of electrons which will emit coherent Čerenkov radiation, known as the Askaryan effect. In this work we study the case in which such a particle shower occurs in a medium just below its surface. We show, for the first time, that the radiation transmitted through the surface is independent of the depth of the shower below the surface when observed from far away, apart from trivial absorption effects. As a direct application we use the recent results of the NuMoon project, where a limit on the neutrino flux for energies above $10^{22}$\,eV was set using the Westerbork Synthesis Radio Telescope by measuring pulsed radio emission from the Moon, to set a limit on the flux of ultra-high-energy cosmic rays.

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