Trans-Planckian particle creation in cosmology and ultrahigh energy cosmic rays

We consider observational constraints on the creation of particles induced by hypothetical trans-Planckian effects during the current stage of the Universe’s expansion. We show that compatibility with the diffuse γ-ray background measured by the EGRET experiment strongly restricts this creation. In particular, it rules out the possibility of detecting signatures of such short-distance effects in anisotropies of the cosmic microwave background radiation. On the other hand, the possibility that some part of ultrahigh-energy cosmic rays originates from new trans-Planckian physics remains open.     

Identifying the spectra of ultrahigh energy cosmic rays from extragalactic sources

The energy spectra of extragalactic sources of cosmic rays are calculated by solving an inverse problem of the transport of cosmic rays with energies of 10¹⁸–10²¹ eV in a Universe filled with background electromagnetic radiation. Calculations are performed using cosmic-ray spectra measured on Earth in Auger experiments. It is assumed that protons and iron nuclei dominate in the composition of a source.     

BL Lacertae are probable sources of the observed ultrahigh energy cosmic rays

We calculate an angular correlation function between ultrahigh energy cosmic rays (UHECR), observed by Yakutsk and AGASA experiments, and the most powerful BL Lacertae objects. We find significant correlations with the probability of statistical fluctuation less than 10^?4, including penalty for selecting the subset of the brightest BL Lacs. We conclude that some of the BL Lacs are sources of the observed UHECR and present a list of the most probable candidates.     

Statistics of clustering of ultrahigh energy cosmic rays and the number of their sources

Observation of clustering of ultrahigh energy cosmic rays (UHECR) suggests that they are emitted by compact sources. Assuming small ( <3 degrees ) deflection of UHECR during the propagation, the statistical analysis of clustering allows an estimate of the spatial density of the sources h(*), including those not yet observed. When applied to astrophysical models involving extragalactic sources, the estimate based on 14 events with energy E>10(20) eV gives h(*) approximately 6x10(-3) Mpc(-3). With increasing statistics, this estimate may lead to exclusion of some models.     

Searching for preferential arrival directions of ultrahigh-energy cosmic rays on the Moscow State University EAS array

There is evidence for possible clustering in the arrival directions of extensive air showers (EASs). A program for analyzing EAS arrival directions has been developed to investigate this problem and the database of the Moscow State University EAS array for 1982–1989 has been analyzed. The distributions in equatorial coordinates have been derived for cosmic rays with energies E ≥ 2 × 10¹⁵ eV and zenith angles <40°. The uniformity of the derived distributions is verified using various statistical tests.     

Pions in primary cosmic rays of ultrahigh energies

In the framework of the Coleman-Glashow hypothesis of an extremely weak violation of Lorentz invariance, neutral and charged pions can be stable for energies above 10¹⁹ eV and enter into the composition of primary cosmic rays of ultrahigh energies. The kinematic exclusion of reactions of pions with relic photons is particularly important, because it allows the Greisen-Zatsepin-Kuzmin paradox to be resolved. The parameters of extensive air showers induced by primary pions calculated within the model of quark-gluon strings with allowance for the Landau-Pomeranchuk-Migdal effect and interactions of neutral pions of ultrahigh energies are not contradictory to the available data of observations. It has been shown that observations of production heights of muons with energies above 10GeV will make it possible to distinguish between primary nuclei, protons, and pions; to verify Lorentz invariance for energies above 10²⁰ eV; and to obtain a new limit on the difference between the maximum possible velocities of muons and pions (c_µ?c_π)<4×10^?26.     

Cosmic rays of ultrahigh energy

A new phenomenon—giant air showers of energy above 10²⁰ eV,which lie beyond the Greisen-Zatsepin-Kuzmin cutoff—was discovered by various detection methods. The mechanism of particle acceleration to such high energies is still a puzzle. The arrival directions of giant showers do not contradict the hypothesis of their isotropic distribution. There are indications of their correlations with distant objects. It is obvious that only observations at new arrays can clarify the problem. The observed events must be reanalyzed within a more elaborate scheme. Verification of slight deviations from Lorentz invariance is possible.     

Pointlike gamma ray sources as signatures of distant accelerators of ultrahigh energy cosmic rays

We discuss the possibility of observing distant accelerators of ultrahigh energy cosmic rays in synchrotron gamma rays. Protons propagating away from their acceleration sites produce extremely energetic electrons during photopion interactions with cosmic microwave background photons. If the accelerator is embedded in a magnetized region, these electrons will emit high energy synchrotron radiation. The resulting synchrotron source is expected to be pointlike, steady, and detectable in the GeV-TeV energy range if the magnetic field is at the nanoGauss level.     

Clusters in the arrival directions of 2×1017-eV cosmic rays detected at the Yakutsk EAS array

Arrival directions of (1.3–4)×10¹⁷-eV cosmic rays detected for zenith angles θ≤53° at the Yakutsk array from 1974 to 2001 are analyzed. These directions exhibit numerous clusters correlating with the supergalactic plane.     

Search for anisotropy in arrival directions of ultrahigh-energy cosmic rays by using the marr wavelet on the equatorial sphere

The arrival direction distribution of cosmic rays for energies E>10¹⁸ eV detected at the Yakutsk EAS array is analyzed using the Marr wavelet. Deviation from the isotropic distribution of 361 showers above 10¹⁹ eV is found at a significance level of 0.007, which corroborates previous evidence of the cosmic ray anisotropy in this energy range. In contrast to the previous methods, the wavelet analysis makes it possible to localize both a celestial-sphere domain containing a supposed source of excess cosmic ray flux and the scale parameter of the two-dimensional wavelet.     

Arrival directions and chemical composition of ultrahigh-energy cosmic rays

Chemical composition of ultrahigh-energy cosmic rays is estimated through the reliably determined (both experimentally and theoretically) distribution of the number of showers in the galactic latitude. Experimental data at energies of ～10¹⁹ eV agree with the theoretical calculations, provided that cosmic rays involve predominantly heavy nuclei. An enhanced flux of cosmic rays from the galactic plane is detected at energies of ～10¹⁹ eV.     

Cosmic rays of energies E 0≥1019 eV and the large-scale structure of the universe

Arrival directions of cosmic rays with energies E ₀≥10¹⁹ eV are analyzed in the supergalactic coordinates. It is shown that increased particle fluxes arrive from the supergalactic plane and regions symmetrically adjoining it at angles ±b _SG≈6.5°. Relatively high densities of clusters of galaxies and quasars, which are related to the large-scale structure of the universe, are observed in these regions.     

Anomalous extensive air showers of ultrahigh energies and their arrival directions

Extensive air showers (EASs) of energy above 8×10¹⁸ eV observed from 1974 to 1995 on the Yakutsk EAS array are analyzed. Showers without muonic component are found. From the arrival directions of these showers, two clusters were found, one of which coincides, within the error bars, with a pulsar in the Milky Way Galaxy.     

Measurement of the flux of ultrahigh energy cosmic rays from monocular observations by the High Resolution Fly's Eye experiment

We have measured the cosmic ray spectrum above 10(17.2) eV using the two air-fluorescence detectors of the High Resolution Fly's Eye observatory operating in monocular mode. We describe the detector, phototube, and atmospheric calibrations, as well as the analysis techniques for the two detectors. We fit the spectrum to a model consisting of galactic and extragalactic sources.