Ariel 6 measurements of ultra-heavy cosmic ray fluxes in the region 34 or = Z or = 48

The Ariel VI satellite was launched by NASA on a Scout rocket on 3rd June 1979 from Wallops Island, Virginia, USA, into a near circular 625 km orbit inclined at 55 deg. It carried a spherical cosmic ray detector designed by a group from Bristol University. A spherical aluminum vessel of diameter 75 cm contains a gas scintillation mixture and a thin spherical shell of Pilot 425 plastic, and forms a single optical cavity viewed by 16 photomultipliers. Particle tracks through the detector may be characterized by their impact parameter p and by whether or not they pass through the cup of plastic scintillator placed between the sphere and the spacecraft body (referred to below as the Anti-Coincidence Detector or ACD). Individual particle charges are determined by separately measuring the gas scintillation and the Cerenkov emission from the plastic shell. This is possible because of the quite different distribution in time of these emissions

Deleting species from model food webs

We use food webs generated by a model to investigate the effects of deleting species on other species in the web and on the web as a whole. The model incorporates a realistic population dynamics, adaptive foragers and other features which allow for the construction of model webs which resemble empirical food webs. A large number of simulations were carried out to produce a substantial number of model webs on which deletion experiments could be performed. We deleted each species in four hundred distinct model webs and determined, on average, how many species were eliminated from the web as a result. Typically only a small number of species became extinct; in no instance was the web close to collapse. Next, we examined how the the probability of extinction of a species depended on its relationship with the deleted species. This involved the exploration of the concept of indirect predator and prey species and the extent that the probability of extinction depended on the trophic level of the two species. The effect of deletions on the web itself was studied by searching for keystone species, whose removal caused a major restructuring of the community, and also by looking at the correlation between a number of food web properties (number of species, linkage density, fraction of omnivores, degree of cycling and redundancy) and the stability of the web to deletions. With the exception of redundancy, we found little or no correlation. In particular, we found no evidence that complexity in terms of increased species number or links per species is destabilising.Comment: 30 pages, 9 figure

Vortex structure in dd-wave superconductors

Vortex structure of pure $d_{x^2-y^2}$-wave superconductors is microscopically analyzed in the framework of the quasi-classical Eilenberger equations. Selfconsistent solution for the $d$-wave pair potential is obtained for the first time in the case of an isolated vortex. The vortex core structure, i.e., the pair potential, the supercurrent and the magnetic field, is found to be fourfold symmetric even in the case that the mixing of $s$-wave component is absent. The detailed temperature dependences of these quantities are calculated. The fourfold symmetry becomes clear when temperature is decreased. The local density of states is calculated for the selfconsistently obtained pair potential. From the results, we discuss the flow trajectory of the quasiparticles around a vortex, which is characteristic in the $d_{x^2-y^2}$-wave superconductors. The experimental relevance of our results to high temperature superconductors is also given.Comment: 22 pages, RevTex, 23 figures available upon reques

Measurements of the Cosmic Ray Composition with Air Shower Experiments

In this paper we review air shower data related to the mass composition of cosmic rays above 10$^{15}$ eV. After explaining the basic relations between air shower observables and the primary mass and energy of cosmic rays, we present different approaches and results of composition studies with surface detectors. Furthermore, we discuss measurements of the longitudinal development of air showers from non-imaging Cherenkov detectors and fluorescence telescopes. The interpretation of these experimental results in terms of primary mass is highly susceptible to the theoretical uncertainties of hadronic interactions in air showers. We nevertheless attempt to calculate the logarithmic mass from the data using different hadronic interaction models and to study its energy dependence from 10$^{15}$ to 10$^{20}$ eV.Comment: 21 pages, invited review accepted for publication in Astroparticle Physics, Topical Issue on Cosmic Ray

First Order Quark-Gluon/Hadron Transition May Affect Cosmological Nucleosynthesis

In the model of a first order quark-gluon/hadron phase transition in which the hadronic phase is considered as vacuum bubbles growing in the quark-gluon background with chiral symmetry broken inside the bubble, we find the estimate for the length scale associated with inhomogeneities originated during the transition, $10$ m $\;\stackrel{<}{\sim }\ell \stackrel{<}{\sim }40$ m, being sufficient to produce significant effects on cosmological nucleosynthesis.Comment: 10 pages, LaTeX, to appear in Phys. Lett. B, 199

The History of Astrophysics in Antarctica

We examine the historical development of astrophysical science in Antarctica from the early 20th century until today. We find three temporally overlapping eras, each having a rather distinct beginning. These are the astrogeological era of meteorite discovery, the high energy era of particle detectors, and the photon astronomy era of microwave, sub--mm and infrared telescopes, sidelined by a few niche experiments at optical wavelengths. The favourable atmospheric and geophysical conditions are briefly examined, followed by an account of the major experiments and a summary of their results.Comment: 29 pages, 10 figures, 1 table Submitted to PASA in April 200

Thermodynamical Bethe Ansatz and Condensed Matter

The basics of the thermodynamic Bethe ansatz equation are given. The simplest case is repulsive delta function bosons, the thermodynamic equation contains only one unknown function. We also treat the XXX model with spin 1/2 and the XXZ model and the XYZ model. This method is very useful for the investigation of the low temperature thermodynamics of solvable systems.Comment: 52 pages, 6 figures, latex, lamuphys.st

Repetition and the prosody-pragmatics interface

Repetition poses certain problems for pragmatics, as evidenced by Sperber and Wilson’s claim that ‘‘the effects of repetition on utterance interpretation are by no means constant’’. This is particularly apposite when we examine repetitions produced in naturally occurring talk. As part of an ongoing study of how phonetics relates to the dynamic evolution of meaning within the sequential organisation of talk-in-interaction, we present a detailed phonetic and pragmatic analysis of a particular kind of self- repetition. The practice of repetition we are concerned with exhibits a range of forms: ‘‘have another go tomorrow . . . have another go tomorrow’’, ‘‘it might do . . . it might do’’, ‘‘it’s a shame . . . it’s a shame’’. The approach we adopt emphasises the necessity of exploring participants’ displayed understandings of pragmatic inferences and attempts not to prejudge the relevance of phonetic (prosodic) parameters. The analysis reveals that speakers draw on a range of phonetic features, including tempo and loudness as well as pitch, in designing these repetitions. The pragmatic function of repetitions designed in this way is to close sequences of talk. Our findings raise a number of theoretical and methodological issues surrounding the prosody– pragmatics interface and participants’ understanding of naturally occurring discourse

Systematics of Leading Particle Production

Using a QCD inspired model developed by our group for particle production, the Interacting Gluon Model (IGM), we have made a systematic analysis of all available data on leading particle spectra. These data include diffractive collisions and photoproduction at HERA. With a small number of parameters (essentially only the non-perturbative gluon-gluon cross section and the fraction of diffractive events) good agreement with data is found. We show that the difference between pion and proton leading spectra is due to their different gluon distributions. We predict a universality in the diffractive leading particle spectra in the large momentum region, which turns out to be independent of the incident energy and of the projectile type.Comment: 13 pages, Latex, 4 ps figures. To appear in Phys. Rev.

High Energy Physics in the Atmosphere: Phenomenology of Cosmic Ray Air Showers

The properties of cosmic rays with energies above 10**6 GeV have to be deduced from the spacetime structure and particle content of the air showers which they initiate. In this review we summarize the phenomenology of these giant air showers. We describe the hadronic interaction models used to extrapolate results from collider data to ultra high energies, and discuss the prospects for insights into forward physics at the LHC. We also describe the main electromagnetic processes that govern the longitudinal shower evolution, as well as the lateral spread of particles. Armed with these two principal shower ingredients and motivation from the underlying physics, we provide an overview of some of the different methods proposed to distinguish primary species. The properties of neutrino interactions and the potential of forthcoming experiments to isolate deeply penetrating showers from baryonic cascades are also discussed. We finally venture into a terra incognita endowed with TeV-scale gravity and explore anomalous neutrino-induced showers.Comment: Typo in caption of Fig. 8 corrected, references adde