Reconstruction of neutrino-induced showers with ANTARES

Op aarde zijn kosmische deeltjes gemeten met extreem hoge energieën. De bijbehorende bronnen we kennen niet, we weten zelfs niet of die misschien binnen ons melkwegstelsel liggen. Wel weten we dat in uitbarstingen van kosmische energie ook neutrino's worden geproduceerd. Boven alle andere deeltjes hebben neutrino’s het voordeel dat ze slechts zwak met materie wisselwerken, waardoor ze ons quasi ongestoord kunnen bereiken. Het detecteren van neutrino’s vereist echter een hoge gevoeligheid in een groot detectorvolume. Voor de ANTARES neutrinotelescoop wordt het heldere water van de Middellandse Zee gebruikt als detectiemedium. We meten de zwakke lichtflitsjes die indirect worden gegenereerd door hoogenergetische neutrino’s. Door alleen te kijken naar deeltjes die door de aarde zijn gereisd kunnen we neutrino’s goed selecteren. Tot nog toe lag de focus van ANTARES op meten van tracks van secundaire deeltjes die geproduceerd worden door slechts één enkel neutrino soort (“flavour”). We hebben de gevoeligheid onderzocht voor de detectie van lokale licht-showers die gegenereerd kunnen worden door alle drie neutrino flavours. Een groot probleem is de overweldigende achtergrond van neutrino’s die in de atmosfeer geproduceerd worden. Door de richting en topologie van showers te karakteriseren hebben we een nieuwe strategie ontwikkeld en deze toegepast op meetgegevens van ANTARES, zodat we de flux (al dan niet limieten) kunnen bepalen voor neutrino’s die voortkomen uit onbekende bronnen. Dergelijke metingen kunnen theorieën over verscheidene ontstaansmechanismes uitsluiten. In de toekomstige, 50 keer gevoeliger KM3NeT telescoop, die meerdere kubieke kilometers water omvat, kan onze strategie nieuw inzicht verschaffen over de bron van kosmische neutrino’s.

Lightning Imaging with LOFAR

We show that LOFAR can be used as a lightning mapping array with a resolution that is orders of magnitude better than existing arrays. In addition the polarization of the radiation can be used to track the direction of the stepping discharges

Measurement of the cosmic ray spectrum above 4×10184{\times}10^{18} eV using inclined events detected with the Pierre Auger Observatory

A measurement of the cosmic-ray spectrum for energies exceeding $4{\times}10^{18}$ eV is presented, which is based on the analysis of showers with zenith angles greater than $60^{\circ}$ detected with the Pierre Auger Observatory between 1 January 2004 and 31 December 2013. The measured spectrum confirms a flux suppression at the highest energies. Above $5.3{\times}10^{18}$ eV, the "ankle", the flux can be described by a power law $E^{-\gamma}$ with index $\gamma=2.70 \pm 0.02 \,\text{(stat)} \pm 0.1\,\text{(sys)}$ followed by a smooth suppression region. For the energy ($E_\text{s}$) at which the spectral flux has fallen to one-half of its extrapolated value in the absence of suppression, we find $E_\text{s}=(5.12\pm0.25\,\text{(stat)}^{+1.0}_{-1.2}\,\text{(sys)}){\times}10^{19}$ eV.Comment: Replaced with published version. Added journal reference and DO

Energy Estimation of Cosmic Rays with the Engineering Radio Array of the Pierre Auger Observatory

The Auger Engineering Radio Array (AERA) is part of the Pierre Auger Observatory and is used to detect the radio emission of cosmic-ray air showers. These observations are compared to the data of the surface detector stations of the Observatory, which provide well-calibrated information on the cosmic-ray energies and arrival directions. The response of the radio stations in the 30 to 80 MHz regime has been thoroughly calibrated to enable the reconstruction of the incoming electric field. For the latter, the energy deposit per area is determined from the radio pulses at each observer position and is interpolated using a two-dimensional function that takes into account signal asymmetries due to interference between the geomagnetic and charge-excess emission components. The spatial integral over the signal distribution gives a direct measurement of the energy transferred from the primary cosmic ray into radio emission in the AERA frequency range. We measure 15.8 MeV of radiation energy for a 1 EeV air shower arriving perpendicularly to the geomagnetic field. This radiation energy -- corrected for geometrical effects -- is used as a cosmic-ray energy estimator. Performing an absolute energy calibration against the surface-detector information, we observe that this radio-energy estimator scales quadratically with the cosmic-ray energy as expected for coherent emission. We find an energy resolution of the radio reconstruction of 22% for the data set and 17% for a high-quality subset containing only events with at least five radio stations with signal.Comment: Replaced with published version. Added journal reference and DO

Measurement of the Radiation Energy in the Radio Signal of Extensive Air Showers as a Universal Estimator of Cosmic-Ray Energy

We measure the energy emitted by extensive air showers in the form of radio emission in the frequency range from 30 to 80 MHz. Exploiting the accurate energy scale of the Pierre Auger Observatory, we obtain a radiation energy of 15.8 \pm 0.7 (stat) \pm 6.7 (sys) MeV for cosmic rays with an energy of 1 EeV arriving perpendicularly to a geomagnetic field of 0.24 G, scaling quadratically with the cosmic-ray energy. A comparison with predictions from state-of-the-art first-principle calculations shows agreement with our measurement. The radiation energy provides direct access to the calorimetric energy in the electromagnetic cascade of extensive air showers. Comparison with our result thus allows the direct calibration of any cosmic-ray radio detector against the well-established energy scale of the Pierre Auger Observatory.Comment: Replaced with published version. Added journal reference and DOI. Supplemental material in the ancillary file

Lightning Imaging with LOFAR

We show that LOFAR can be used as a lightning mapping array with a resolution that is orders of magnitude better than existing arrays. In addition the polarization of the radiation can be used to track the direction of the stepping discharges