A reinterpretation of Volcano Ranch lateral distribution measurements to infer the mass composition of cosmic rays

In the course of its operation, the Volcano Ranch array collected data on the lateral distribution of showers produced by cosmic rays at energies above $10^{17}$ {\rm eV}. From these data very precise measurements of the steepness of the lateral distribution function, characterized by the $\eta$ parameter, were made. The current availability of sophisticated hadronic interaction models has prompted a reinterpretation of the measurements. We use the interaction models {\sc qgsjet} and {\sc sibyll} in the {\sc aires} Monte Carlo code to generate showers together with {\sc geant4} to simulate the response of the detectors to ground particles. As part of an effort to estimate the primary mass composition of cosmic rays at this energy range, we present the results of our preliminary analysis of the distribution of $\eta$.Comment: 4 pages, 5 figures Talk presented at the XII International Symposium on Very High Energy Cosmic Ray Interactions, CERN 2002. To be published in Nucl. Phys. B (Proc. Suppl.

The rate of cosmic ray showers at large zenith angles: a step towards the detection of ultra-high energy neutrinos by the Pierre Auger Observatory

It is anticipated that the Pierre Auger Observatory can be used to detect cosmic neutrinos of >10^19 eV that arrive at very large zenith angles. However showers created by neutrino interactions close to the detector must be picked out against a background of similar events initiated by cosmic ray nuclei. As a step towards understanding this background, we have made the first detailed analysis of air showers recorded at Haverah Park (an array which used similar detectors to those planned for the Auger Observatory) with zenith angles above 60 degs. We find that the differential shower rate from 60 degs to 80 degs. can be predicted accurately when we adopt the known primary energy spectrum above 10^17 eV and assume the QGSJET model and proton primaries. Details of the calculation are given.Comment: 22 pages, 12 figures, to appear in Astroparticle Physic

Spectra of hadrons and muons in the atmosphere: primary spectra, characteristics of hadron-air interactions

Self-consistency of interaction models QGSJET 01, SIBYLL 2.1, NEXUS 3.97 and QGSJET II is checked in terms of their ability to reproduce simultaneously experimental data on fluxes of muons and hadrons. From this point of view SIBYLL 2.1 gives the most acceptable, though not quite satisfactory, results. Analysis of the situation for muons supports our previous conclusions, that high-energy muon deficit is due both to underestimation of primary light nuclei fluxes in direct emulsion chamber experiments and to softness of $p+A\to\pi^\pm,K^\pm+X$ inclusive spectra in fragmentation region, especially prominent in case of QGSJET 01 model.Comment: Talk given at the XIVth ISVHECRI (Weihai, China, 2006

Mass Composition of Cosmic Rays in the Range 2 x 10^17 - 3 x 10^18 Measured with Haverah Park Array

At the Haverah Park Array a number of air shower observables were measured that are relevant to the determination of the mass composition of cosmic rays. In this paper we discuss measurements of the risetime of signals in large area water-Cherenkov detectors and of the lateral distribution function of the water-Cherenkov signal. The former are used to demonstrate that the CORSIKA code, using the QGSJET98 model, gives an adequate description of the data with a low sensitivity, in this energy range, to assumptions about primary mass. By contrast the lateral distribution is sufficiently well measured that there is mass sensitivity. We argue that in the range 0.2-1.0 EeV the data are well represented with a bi-modal composition of 34+-2 % protons and the rest iron. We also discuss the systematic errors induced by the choice of hadronic model.Comment: 16 pages, 13 figures. Accepted for publication in Astroparticle Physic

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

Air Shower Simulations in a Hybrid Approach using Cascade Equations

A new hybrid approach to air shower simulations is described. At highest energies, each particle is followed individually using the traditional Monte Carlo method; this initializes a system of cascade equations which are applicable for energies such that the shower is one-dimensional. The cascade equations are solved numerically down to energies at which lateral spreading becomes significant, then their output serves as a source function for a 3-dimensional Monte Carlo simulation of the final stage of the shower. This simulation procedure reproduces the natural fluctuations in the initial stages of the shower, gives accurate lateral distribution functions, and provides detailed information about all low energy particles on an event-by-event basis. It is quite efficient in computation time.Comment: 19 Pages, 10 Figures accepted version with more explanations about source functions, in print PR

Polynomial form of the Hilbert-Einstein action

Configuration space of general relativity is extended by inclusion of the determinant of the metric as a new independent variable. As the consequence the Hilbert-Einstein action takes a polynomial form.Comment: 8 pages, references added and correcte

Функция Грина в гравистатике Эйнштейна

We apply the method of Green's function to generating axisymmetric static solutions to Einstein's equations.В статье применяется метод функции Грина для построения статических аксиально-симметричных решений уравнений Эйнштейна

Large closed queueing networks in semi-Markov environment and its application

The paper studies closed queueing networks containing a server station and $k$ client stations. The server station is an infinite server queueing system, and client stations are single-server queueing systems with autonomous service, i.e. every client station serves customers (units) only at random instants generated by a strictly stationary and ergodic sequence of random variables. The total number of units in the network is $N$. The expected times between departures in client stations are $(N\mu_j)^{-1}$. After a service completion in the server station, a unit is transmitted to the $j$th client station with probability $p_{j}$ $(j=1,2,...,k)$, and being processed in the $j$th client station, the unit returns to the server station. The network is assumed to be in a semi-Markov environment. A semi-Markov environment is defined by a finite or countable infinite Markov chain and by sequences of independent and identically distributed random variables. Then the routing probabilities $p_{j}$ $(j=1,2,...,k)$ and transmission rates (which are expressed via parameters of the network) depend on a Markov state of the environment. The paper studies the queue-length processes in client stations of this network and is aimed to the analysis of performance measures associated with this network. The questions risen in this paper have immediate relation to quality control of complex telecommunication networks, and the obtained results are expected to lead to the solutions to many practical problems of this area of research.Comment: 35 pages, 1 figure, 12pt, accepted: Acta Appl. Mat

Structural effects in UO2 thin films irradiated with fission-energy Xe ions

Uranium dioxide thin films have been successfully grown on LSAT (Al10La3O51Sr14Ta7) substrates by reactive magnetron sputtering. Irradiation by 92 MeV 129Xe23+ ions to simulate fission damage that occurs within nuclear fuels caused microstructural and crystallographic changes. Initially flat and continuous thin films were produced by magnetron sputtering with a root mean square roughness of 0.35 nm determined by AFM. After irradiation, this roughness increased to 60–70 nm, with the films developing discrete microstructural features: small grains (∼3 μm), along with larger circular (up to 40 μm) and linear formations with non-uniform composition according to the SEM, AFM and EDX results. The irradiation caused significant restructuring of the UO2 films that was manifested in significant film-substrate mixing, observed through EDX analysis. Diffusion of Al from the substrate into the film in unirradiated samples was also observed