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.

On one master integral for three-loop on-shell HQET propagator diagrams with mass

An exact expression for the master integral I_2 arising in three-loop on-shell HQET propagator diagrams with mass is derived and its analytical expansion in the dimensional regularization parameter epsilon is given.Comment: 6 pages, 1 figure; v3: completely re-written, 2 new authors, many new results, additional reference

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

Multiple (inverse) binomial sums of arbitrary weight and depth and the all-order epsilon-expansion of generalized hypergeometric functions with one half-integer value of parameter

We continue the study of the construction of analytical coefficients of the epsilon-expansion of hypergeometric functions and their connection with Feynman diagrams. In this paper, we show the following results: Theorem A: The multiple (inverse) binomial sums of arbitrary weight and depth (see Eq. (1.1)) are expressible in terms of Remiddi-Vermaseren functions. Theorem B: The epsilon expansion of a hypergeometric function with one half-integer value of parameter (see Eq. (1.2)) is expressible in terms of the harmonic polylogarithms of Remiddi and Vermaseren with coefficients that are ratios of polynomials. Some extra materials are available via the www at this http://theor.jinr.ru/~kalmykov/hypergeom/hyper.htmlComment: 24 pages, latex with amsmath and JHEP3.cls; v2: some typos corrected and a few references added; v3: few references added

The exposure of the hybrid detector of the Pierre Auger Observatory

The Pierre Auger Observatory is a detector for ultra-high energy cosmic rays. It consists of a surface array to measure secondary particles at ground level and a fluorescence detector to measure the development of air showers in the atmosphere above the array. The "hybrid" detection mode combines the information from the two subsystems. We describe the determination of the hybrid exposure for events observed by the fluorescence telescopes in coincidence with at least one water-Cherenkov detector of the surface array. A detailed knowledge of the time dependence of the detection operations is crucial for an accurate evaluation of the exposure. We discuss the relevance of monitoring data collected during operations, such as the status of the fluorescence detector, background light and atmospheric conditions, that are used in both simulation and reconstruction.Comment: Paper accepted by Astroparticle Physic

Upper limit on the cosmic-ray photon fraction at EeV energies from the Pierre Auger Observatory

From direct observations of the longitudinal development of ultra-high energy air showers performed with the Pierre Auger Observatory, upper limits of 3.8%, 2.4%, 3.5% and 11.7% (at 95% c.l.) are obtained on the fraction of cosmic-ray photons above 2, 3, 5 and 10 EeV (1 EeV = 10^18 eV) respectively. These are the first experimental limits on ultra-high energy photons at energies below 10 EeV. The results complement previous constraints on top-down models from array data and they reduce systematic uncertainties in the interpretation of shower data in terms of primary flux, nuclear composition and proton-air cross-section.Comment: 20 pages, 7 figures, 2 tables. Minor changes. Accepted by Astroparticle Physic

Generation potential of kerogen of the Bazhenov formation and possibility of its implementation

Bazhenov formation is one of the most well-known and potentially productive Russian oil shale formations. However, conventional methods often do not provide oil flow rate from the formation. Therefore, in recent years, studies are devoted to development of new methods for oil production and the alternate potentials of the Bazhenov formation exploration. The article describes generation potential of kerogen, that shows the amount of hydrocarbon compounds which could form in the reservoir after a long period of time as a result of katagenesis, and the results of the thermal effect on the rock samples in the laboratory for synthetic oil production by implementing generation potential. It was shown that synthetic oil is produced by the heat of Bazhenov formation samples in a closed system during 7 days in presence of water in the temperature range from 250°C to 350°C, oil amount may reach 25 mg HC/g of rock (~3 wt.% of the sample). The maximum oil yield was at 300°C, but the composition of petroleum products varies with temperature changes. It was found that depending on the stage of katagenetic transformation duration of heating for maximum yield of hydrocarbon compounds recovery varies from a few days for inmature kerogen to two weeks for highly maturated one. It was demonstrated that secondary cracking of products, which can occur at advanced temperatures and prolonged exposure should been taken into account when optimal heating conditions are selected. Hydrocarbon systems composition analysis showed that synthetic oil is comparable with natural oil and different from the chloroform extract, and heating conditions alteration allows to control the composition of produced oil that may be promising for use in the petroleum and chemical industries. Thus, the method of synthetic crude oil production by implementation of the generation capacity of kerogen by thermal stimulation in the presence of water with 80% of generation potential released was proposed

Methods of step extraction of rocks of high-carbon formations for the study of the component distribution of bitumen and variability of their basic geochemical parameters

The article describes organic-rich rocks sequential extraction method for the bitumen composition difference. The method step-by-step extracts bitumen first from open and then from closed pores using three organic solvents with increasing polarity. The released bitumen differs in malthens/asphaltenes ratio, the distribution of n-alkanes, the content of terpanes and steranes, and, thus, the values of the biomarker parameters. These parameters show difference in the degree of organic matter thermal maturity, which is relates to different types of rock pore space. At the same time different parameters show different maturity ratio between bitumen from open and closed pores. Changes in the composition of bitumen allow to estimate the migration of hydrocarbon compounds through the well, to investigate the effect of sedimentation conditions on the pore space and the distribution of bitumen. The results show that investigation of bitumen received by one-step extraction from powder can lead to incorrect interpret of obtained results

Pore Space Change of Various Lithotypes of the Kerogen Domanic Rocks at Different Heating Rates

The results of pore space changes as a result of heating Domanik Formation rock samples at different heating rates are shown. Microtomography method revealed that after heating in significant changes may arise, lens-like large pores can be formed, the number of pores and their coherence increase. It was found that changes in the pore space depend on the texture of rocks, the amount of organic matter and its degree of maturity, with all the factors must be considered together. Heating rate also influences the change in the pore space. The results should been considered in the retrieving of the natural reservoirs formation

Evidence of carbonate rocks formation on geochemical barriers in black shale on the example of the Bazhenov formation of the Western Siberia

A comprehensive lithological-geochemical study of rocks of the Upper Jurassic-Lower Cretaceous blackshale Bazhenov formation showed that most of its carbonatized interlayers to the boundaries of packs of different composition differing in carbonate content, degree of siliceousness or clayiness. At the same time, at the boundaries of the Bazhenov formation with host sediments, where carbonate rocks are often found in association with “pyrite” low carbon rocks according to geochemical parameters (degree of pyritization, Mn/Al, Ua), a change in the redox regime is recorded. In the most studied stratum at intervals of occurrence of carbonates, a change in the redox regime is not observed. It is assumed that they existed alkaline barriers, as evidenced by the change in the composition of rocks. The following geochemical barriers (bottom-up along the section) were identified in the Bazhenov formation and its transition to the enclosing sediments, on which evidence of localization of carbonate minerals was found: redox barrier 1 (lower BF boundary), alkaline barrier 1 (border of mixes of kerogen - clay-siliceous low-carbonate and silicites), alkaline barrier 2 (border of kerogen-clay-siliceous low-carbonate and siliceous-carbonate “coccolith” packs); Redox barrier 2 (the upper limit of the BF)