The reactor antineutrino anomaly might be explained by the oscillation of reactor antineutrinos toward a sterile neutrino of eV mass. In order to explore this hypothesis, the STEREO experiment ...measures the antineutrino energy spectrum in six different detector cells covering baselines between 9 and 11 m from the compact core of the ILL research reactor. In this Letter, results from 66 days of reactor turned on and 138 days of reactor turned off are reported. A novel method to extract the antineutrino rates has been developed based on the distribution of the pulse shape discrimination parameter. The test of a new oscillation toward a sterile neutrino is performed by comparing ratios of cells, independent of absolute normalization and of the prediction of the reactor spectrum. The results are found to be compatible with the null oscillation hypothesis and the best fit of the reactor antineutrino anomaly is excluded at 97.5% C.L.
In the present paper we stress some characteristics of the electric field produced by a point-charge-like air shower developing in an atmosphere of refractive index fixed to unity and restricting ...ourselves to the charge excess and geosynchrotron terms. The aim of this toy model is obviously not to compete with refined theories nor full Monte Carlo simulations but to understand the main features of radio emission process as observed in recent experiments, in particular the field polarization effects. In this simplified frame, the antenna radio time pulse for vertical or inclined showers is merely given by the product of two analytical functions. The calculation time is reduced to a fraction of a second. The analytical pulse amplitudes are relatively close to those obtained with the ReAIRES code. Further works must be carried out to evaluate the limitations and the possible extensions of this toy model.
A detection technique for ultra-high-energy cosmic rays, complementary to the fluorescence technique, would be the use of the molecular bremsstrahlung radiation emitted by low-energy ionization ...electrons left after the passage of the showers in the atmosphere. In this article, a detailed estimate of the spectral intensity of photons at ground level originating from this radiation is presented. The spectral intensity expected from the passage of the high-energy electrons of the cascade is also estimated. The absorption of the photons in the plasma of electrons and neutral molecules is shown to be negligible. The obtained spectral intensity is shown to be 2x10 super(-21)Wcm super(-2)GHz super(-1) at 10 km from the shower core for a vertical shower induced by a proton of 10 super(17.5)eV. In addition, a recent measurement of bremsstrahlung radiation in air at gigahertz frequencies from a beam of electrons produced at 95 keV by an electron gun is also discussed and reasonably reproduced by the model.
We have developed a self powered stand alone particle detector array dedicated to the observation of horizontal tau air showers induced by high energy neutrinos interacting in mountain rock. Air ...shower particle detection reaches a 100% duty cycle and is practically free of background when compared to Cherenkov light or radio techniques. It is thus better suited for rare neutrino event search. An appropriate mountain to valley topological configuration has been identified and the first array will be deployed on an inclined slope at an elevation of 1500 m facing Southern Alps near the city of Grenoble (France). A full simulation has been performed. A neutrino energy dependent mountain tomography chart is obtained using a neutrino and tau propagation code together with a detailed cartography and elevation map of the region. The array acceptance is then evaluated between 1 PeV and 100 EeV by simulating decaying tau air showers across the valley. The effective detection surface is determined by the shower lateral extension at array location and is hence much larger than the array geometrical area. The array exposure will be 10 14 cm2 sr s at 100 PeV. Several independent arrays can be deployed with the aim of constituting a large distributed observatory. Some other sites are already under study. At last, special care is dedicated to the educational and outreach aspects of such a cosmic ray detector.
Abstract We present a measurement of the cosmic-ray spectrum above 100 PeV using the part of the surface detector of the Pierre Auger Observatory that has a spacing of 750 m. An inflection of the ...spectrum is observed, confirming the presence of the so-called second-knee feature. The spectrum is then combined with that of the 1500 m array to produce a single measurement of the flux, linking this spectral feature with the three additional breaks at the highest energies. The combined spectrum, with an energy scale set calorimetrically via fluorescence telescopes and using a single detector type, results in the most statistically and systematically precise measurement of spectral breaks yet obtained. These measurements are critical for furthering our understanding of the highest energy cosmic rays.
We present the GIGAS (Gigahertz Identification of Giant Air Shower) microwave radio sensor arrays of the EASIER project (Extensive Air Shower Identification with Electron Radiometers), deployed at ...the site of the Pierre Auger cosmic ray observatory. The aim of these novel arrays is to probe the intensity of the molecular bremsstrahlung radiation expected from the development of the extensive air showers produced by the interaction of ultra high energy cosmic rays in the atmosphere. In the designed setup, the sensors are embedded within the surface detector array of the Pierre Auger observatory allowing us to use the particle signals at ground level to trigger the radio system. A series of seven, then 61 sensors have been deployed in the C-band, followed by a new series of 14 higher sensitivity ones in the C-band and the L-band. The design, the operation, the calibration and the sensitivity to extensive air showers of these arrays are described in this paper.
The new setup of the CODALEMA experiment installed at the Radio Observatory in Nançay, France, is described. It includes broadband active dipole antennas and an extended and upgraded particle ...detector array. The latter gives access to the air shower energy, allowing us to compute the efficiency of the radio array as a function of energy. We also observe a large asymmetry in counting rates between showers coming from the North and the South in spite of the symmetry of the detector. The observed asymmetry can be interpreted as a signature of the geomagnetic origin of the air shower radio emission. A simple linear dependence of the electric field with respect to
v
∧
B is used which reproduces the angular dependencies of the number of radio events and their electric polarity.
Abstract The hybrid design of the Pierre Auger Observatory allows for the measurement of the properties of extensive air showers initiated by ultra-high energy cosmic rays with unprecedented ...precision. By using an array of prototype underground muon detectors, we have performed the first direct measurement, by the Auger Collaboration, of the muon content of air showers between $$2\times 10^{17}$$ 2×1017 and $$2\times 10^{18}$$ 2×1018 eV. We have studied the energy evolution of the attenuation-corrected muon density, and compared it to predictions from air shower simulations. The observed densities are found to be larger than those predicted by models. We quantify this discrepancy by combining the measurements from the muon detector with those from the Auger fluorescence detector at $$10^{{17.5}}\, {\mathrm{eV}} $$ 1017.5eV and $$10^{{18}}\, {\mathrm{eV}} $$ 1018eV . We find that, for the models to explain the data, an increase in the muon density of $$38\%$$ 38% $$\pm 4\% (12\%)$$ ±4%(12%) $$\pm {}^{21\%}_{18\%}$$ ±18%21% for EPOS-LHC, and of $$50\% (53\%)$$ 50%(53%) $$\pm 4\% (13\%)$$ ±4%(13%) $$\pm {}^{23\%}_{20\%}$$ ±20%23% for QGSJetII-04, is respectively needed.
Radio emission modelization—Observables and interpretation Rivière, C.; Chauvin, J.; Montanet, F. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
2012, Letnik:
662
Journal Article
Recenzirano
Radio detection techniques of extensive air shower are currently being reinvested. Experiment with unprecedented quality of data are ongoing and different emission models are being investigated. We ...report here two complementary approaches of the geosynchrotron emission, trying to emphasize field features which can be confronted to experimental data or help its interpretation – among which a −
v×
B dependency.
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