22 research outputs found
New constraints on the mass composition of cosmic rays above 10^17 eV from Volcano Ranch measurements
Linsley used the Volcano Ranch array to collect data on the lateral
distribution of showers produced by cosmic rays at energies above 10^17 eV.
Very precise measurements of the steepness of the lateral distribution function
were made on 366 events. The current availability of sophisticated hadronic
interaction models has prompted an interpretation of the measurements. In this
analysis we use the AIRES Monte Carlo code to generate showers, together with
GEANT4 to simulate the detector response to ground particles. The results show
that, with the assumption of a bi-modal proton and iron mix, iron is the
dominant component of cosmic rays between 5x10^17 and 10^19 eV, assuming that
hadronic interactions are well-described by QGSJET at this energy range.Comment: Submitted to Astropart. Phy
Anisotropy studies around the galactic centre at EeV energies with the Auger Observatory
Data from the Pierre Auger Observatory are analyzed to search for
anisotropies near the direction of the Galactic Centre at EeV energies. The
exposure of the surface array in this part of the sky is already significantly
larger than that of the fore-runner experiments. Our results do not support
previous findings of localized excesses in the AGASA and SUGAR data. We set an
upper bound on a point-like flux of cosmic rays arriving from the Galactic
Centre which excludes several scenarios predicting sources of EeV neutrons from
Sagittarius . Also the events detected simultaneously by the surface and
fluorescence detectors (the `hybrid' data set), which have better pointing
accuracy but are less numerous than those of the surface array alone, do not
show any significant localized excess from this direction.Comment: Matches published versio