713 research outputs found
Estimate of the correlation signal between cosmic rays and BL Lacs in future data
The existing correlation between BL Lacertae objects (BL Lacs) and cosmic-ray
events observed by HiRes experiment provide sufficient information to formulate
quantitatively the hypothesis about the flux of neutral cosmic-ray particles
originated from BL Lacs. We determine the potential of future cosmic ray
experiments to test this hypothesis by predicting the number of coincidences
between arrival directions of cosmic rays and positions of BL Lacs on the
celestial sphere, which should be observed in the future datasets. We find that
the early Pierre Auger data will not have enough events to address this
question. On the contrary, the final Pierre Auger data and the early Telescope
Array data will be sufficient to fully test this hypothesis. If confirmed, it
would imply the existence of highest-energy neutral particles coming from
cosmological distances.Comment: 5 page
Sensitivity of cosmic-ray experiments to ultra-high-energy photons: reconstruction of the spectrum and limits on the superheavy dark matter
We estimate the sensitivity of various experiments detecting
ultra-high-energy cosmic rays to primary photons with energies above 10^19 eV.
We demonstrate that the energy of a primary photon may be significantly (up to
a factor of ~ 10) under- or overestimated for particular primary energies and
arrival directions. We consider distortion of the reconstructed cosmic-ray
spectrum for the photonic component. As an example, we use these results to
constrain the parameter space of models of superheavy dark matter by means of
both the observed spectra and available limits on the photon content. We find
that a significant contribution of ultra-high-energy particles (photons and
protons) from decays of superheavy dark matter is allowed by all these
constraints.Comment: 18 pages, 7 figure
Evidence for a connection between the gamma-ray and the highest energy cosmic-ray emissions by BL Lacertae objects
A set of potentially gamma-ray--loud BL Lac objects is selected by
intersecting the EGRET and BL Lac catalogs. Of the resulting 14 objects, eight
are found to correlate with arrival directions of ultra--high-energy cosmic
rays (UHECRs), with significance of the order of 5 sigma. This suggests that
gamma-ray emission can be used as a distinctive feature of those BL Lac objects
that are capable of producing UHECR.Comment: 11 pages, 1 figure, version published in APJ Letter
Testing the correlations between ultra-high-energy cosmic rays and BL Lac type objects with HiRes stereoscopic data
Previously suggested correlations of BL Lac type objects with the arrival
directions of the ultra-high-energy cosmic ray primaries are tested by making
use of the HiRes stereoscopic data. The results of the study support the
conclusion that BL Lacs may be the cosmic ray sources and suggest the presence
of a small (a few percent) fraction of neutral primaries at E>10^{19} eV.Comment: 4 pages, 3 figure
Muon lateral distribution function of extensive air showers: results of the Sydney University Giant Air-shower Recorder versus modern Monte-Carlo simulations
The Sydney University Giant Air-shower Recorder (SUGAR) measured the muon
component of extensive air showers with a unique array of muon detectors. The
SUGAR data allow us to reconstruct the empirical dependence of muon density on
the distance from the axis of the shower, the lateral distribution function
(LDF). We compare the shape of this function with the predictions of
hadronic-interaction models, QGSJET-II-04 and EPOS-LHC, in the energy range
10^17.6 - 10^18.6 eV. We find a difference between the observed data and the
simulation: the observed muon density falls faster with the increased core
distance than it is predicted in simulations. This observation may be important
for interpretation of the energy-dependent discrepancies in the simulated and
observed numbers of muons in air showers, known as the "muon excess".Comment: 7 pages revtex, 4 figures (7 panels). V2: discussion of systematic
uncertainties added, results unchanged. Version accepted by Phys. Rev.
Deuteron tensor polarization component T_20(Q^2) as a crucial test for deuteron wave functions
The deuteron tensor polarization component T_20(Q^2) is calculated by
relativistic Hamiltonian dynamics approach. It is shown that in the range of
momentum transfers available in to-day experiments, relativistic effects, meson
exchange currents and the choice of nucleon electromagnetic form factors almost
do not influence the value of T_20(Q^2). At the same time, this value depends
strongly on the actual form of the deuteron wave function, that is on the model
of NN-interaction in deuteron. So the existing data for T_20(Q^2) provide a
crucial test for deuteron wave functions.Comment: 11 pages, 3 figure
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