8 research outputs found
A Search for Photons with Energies Above 2X10(17) eV Using Hybrid Data from the Low-Energy Extensions of the Pierre Auger Observatory
Ultra-high-energy photons with energies exceeding 10(17) eV offer a wealth of connections to different aspects of cosmic-ray astrophysics as well as to gamma-ray and neutrino astronomy. The recent observations of photons with energies in the 10(15) eV range further motivate searches for even higher-energy photons. In this paper, we present a search for photons with energies exceeding 2 x 10(17) eV using about 5.5 yr of hybrid data from the low-energy extensions of the Pierre Auger Observatory. The upper limits on the integral photon flux derived here are the most stringent ones to date in the energy region between 10(17) and 10(18) eV
Nucleon transfer in highly mass-asymmetric reaction systems between197au and relatively light projectiles in the energy region below 10 MeV/u
A SEARCH FOR POINT SOURCES OF EeV PHOTONS
Measurements of air showers made using the hybrid technique developed with the fluorescence and surface detectors of the Pierre Auger Observatory allow a sensitive search for point sources of EeV photons anywhere in the exposed sky. A multivariate analysis reduces the background of hadronic cosmic rays. The search is sensitive to a declination band from -85° to +20°, in an energy range from 1017.3 eV to 1018.5 eV. No photon point source has been detected. An upper limit on the photon flux has been derived for every direction. The mean value of the energy flux limit that results from this, assuming a photon spectral index of -2, is 0.06 eV cm-2 s -1, and no celestial direction exceeds 0.25 eV cm-2 s -1. These upper limits constrain scenarios in which EeV cosmic ray protons are emitted by non-transient sources in the Galax
Data-driven estimation of the invisible energy of cosmic ray showers with the Pierre Auger Observatory
The determination of the primary energy of extensive air showers using the
fluorescence detection technique requires an estimation of the energy carried
away by particles that do not deposit all their energy in the atmosphere. This
estimation is typically made using Monte Carlo simulations and thus depends on
the assumed primary particle mass and on model predictions for neutrino and
muon production. In this work we present a new method to obtain the invisible
energy from events detected by the Pierre Auger Observatory. The method uses
measurements of the muon number at ground level, and it allows us to reduce
significantly the systematic uncertainties related to the mass composition and
the high energy hadronic interaction models, and consequently to improve the
estimation of the energy scale of the Observatory.Comment: Published version, 18 pages, 10 figures, 4 table