Sensitivity of lunar particle-detection experiments

The use of the Moon as a detector volume for ultra-high-energy neutrinos and cosmic rays, by searching for the Askaryan radio pulse produced when they interact in the lunar regolith, has been attempted by a range of projects over the past two decades. In this contribution, I discuss some of the technical considerations relevant to these experiments, and their consequent sensitivity to ultra-high-energy particles. I also discuss some possible future experiments, and highlight their potential.Comment: To be published in the Proceedings of the ARENA2016 conference, Groningen, The Netherland

Corrections to Scaling in the Phase-Ordering Dynamics of a Vector Order Parameter

Corrections to scaling, associated with deviations of the order parameter from the scaling morphology in the initial state, are studied for systems with O(n) symmetry at zero temperature in phase-ordering kinetics. Including corrections to scaling, the equal-time pair correlation function has the form C(r,t) = f_0(r/L) + L^{-omega} f_1(r/L) + ..., where L is the coarsening length scale. The correction-to-scaling exponent, omega, and the correction-to-scaling function, f_1(x), are calculated for both nonconserved and conserved order parameter systems using the approximate Gaussian closure theory of Mazenko. In general, omega is a non-trivial exponent which depends on both the dimensionality, d, of the system and the number of components, n, of the order parameter. Corrections to scaling are also calculated for the nonconserved 1-d XY model, where an exact solution is possible.Comment: REVTeX, 20 pages, 2 figure

Unwinding Scaling Violations in Phase Ordering

The one-dimensional $O(2)$ model is the simplest example of a system with topological textures. The model exhibits anomalous ordering dynamics due to the appearance of two characteristic length scales: the phase coherence length, $L \sim t^{1/z}$, and the phase winding length, $L_{w} \sim L^{\chi}$. We derive the scaling law $z=2+\mu\chi$, where $\mu=0$ ($\mu=2$) for nonconserved (conserved) dynamics and $\chi=1/2$ for uncorrelated initial orientations. From hard-spin equations of motion, we consider the evolution of the topological defect density and recover a simple scaling description. (please email [email protected] for a hard copy by mail)Comment: 4 pages, LATeX, uuencoded figure file appended: needs epsf.sty, [resubmitted since postscript version did not work well], M/C.TH.94/21,NI9402

Velocity Distribution of Topological Defects in Phase-Ordering Systems

The distribution of interface (domain-wall) velocities ${\bf v}$ in a phase-ordering system is considered. Heuristic scaling arguments based on the disappearance of small domains lead to a power-law tail, $P_v(v) \sim v^{-p}$ for large v, in the distribution of $v \equiv |{\bf v}|$. The exponent p is given by $p = 2+d/(z-1)$, where d is the space dimension and 1/z is the growth exponent, i.e. z=2 for nonconserved (model A) dynamics and z=3 for the conserved case (model B). The nonconserved result is exemplified by an approximate calculation of the full distribution using a gaussian closure scheme. The heuristic arguments are readily generalized to conserved case (model B). The nonconserved result is exemplified by an approximate calculation of the full distribution using a gaussian closure scheme. The heuristic arguments are readily generalized to systems described by a vector order parameter.Comment: 5 pages, Revtex, no figures, minor revisions and updates, to appear in Physical Review E (May 1, 1997

Limits on the validity of the thin-layer model of the ionosphere for radio interferometric calibration

For a ground-based radio interferometer observing at low frequencies, the ionosphere causes propagation delays and refraction of cosmic radio waves which result in phase errors in the received signal. These phase errors can be corrected using a calibration method that assumes a two-dimensional phase screen at a fixed altitude above the surface of the Earth, known as the thin-layer model. Here we investigate the validity of the thin-layer model and provide a simple equation with which users can check when this approximation can be applied to observations for varying time of day, zenith angle, interferometer latitude, baseline length, ionospheric electron content and observing frequency.Comment: 8 pages, 10 figures, accepted MNRA

Minimal prospects for radio detection of extensive air showers in the atmosphere of Jupiter

One possible approach for detecting ultra-high-energy cosmic rays and neutrinos is to search for radio emission from extensive air showers created when they interact in the atmosphere of Jupiter, effectively utilizing Jupiter as a particle detector. We investigate the potential of this approach. For searches with current or planned radio telescopes we find that the effective area for detection of cosmic rays is substantial (~3*10^7 km^2), but the acceptance angle is so small that the typical geometric aperture (~10^3 km^2 sr) is less than that of existing terrestrial detectors, and cosmic rays also cannot be detected below an extremely high threshold energy (~10^23 eV). The geometric aperture for neutrinos is slightly larger, and greater sensitivity can be achieved with a radio detector on a Jupiter-orbiting satellite, but in neither case is this sufficient to constitute a practical detection technique. Exploitation of the large surface area of Jupiter for detecting ultra-high-energy particles remains a long-term prospect that will require a different technique, such as orbital fluorescence detection.Comment: 15 pages, 15 figures, 2 tables, accepted for publication in Ap

Approach to Asymptotic Behaviour in the Dynamics of the Trapping Reaction

We consider the trapping reaction A + B -> B in space dimension d=1, where the A and B particles have diffusion constants D_A, D_B respectively. We calculate the probability, Q(t), that a given A particle has not yet reacted at time t. Exploiting a recent formulation in which the B particles are eliminated from the problem we find, for t -> \infty, $Q(t) \sim \exp[-(4/\sqrt{\pi})(\rho^2 D_Bt)^{1/2} - (C \rho^2 D_A t)^{1/3} + ...]$, where $\rho$ is the density of B particles and $C \propto D_A/D_B$ for $D_A/D_B << 1$.Comment: 8 pages, 2 figures; minor change

International lung cancer trends by histologic type: male:female differences diminishing and adenocarcinoma rates rising.

Lung cancer rates have peaked among men in many areas of the world, but rates among women continue to rise. Most lung cancers are squamous cell carcinoma, small cell carcinoma, or adenocarcinoma; trends vary according to type. We compiled population-based morphology-specific incidence data from registries contributing to the International Agency for Research on Cancer (IARC) databases. Unspecified cancers and carcinomas were reallocated based on a registry, time period, sex and age group-specific basis. Where available, data from several registries within a country were pooled for analysis. Rates per 100,000 person-years for 1980-1982 to 1995-1997 were age-adjusted by the direct method using the world standard. Squamous cell carcinoma rates among males declined 30% or more in North America and some European countries while changing less dramatically in other areas; small cell carcinoma rates decreased less rapidly. Squamous and small cell carcinoma rates among females generally rose, with the increases especially pronounced in the Netherlands and Norway. In contrast, adenocarcinoma rates rose among males and females in virtually all areas, with the increases among males exceeding 50% in many areas of Europe; among females, rates also rose rapidly and more than doubled in Norway, Italy and France. Rates of all lung cancer types among women and adenocarcinoma among men continue to rise despite declining cigarette use in many Western countries and shifts to filtered/low-tar cigarettes. Renewed efforts toward cessation and prevention are mandatory to curb the prevalence of cigarette smoking and to reduce lung cancer rates eventually

Statistical modelling for prediction of axis-switching in rectangular jets

Rectangular nozzles are increasingly used for modern military aircraft propulsion installations, including the roll nozzles on the F-35B vertical/short take-off and landing strike fighter. A peculiar phenomenon known as axis-switching is generally observed in such non-axisymmetric nozzle flows during which the jet spreads faster along the minor axis compared to the major axis. This might affect the under-wing stores and aircraft structure. A computational fluid dynamics study was performed to understand the effects of changing the upstream nozzle geometry on a rectangular free jet. A method is proposed, involving the formulation of an equation based upon a statistical model for a rectangular nozzle with an exit aspect ratio (ARe) of 4; the variables under consideration (for a constant nozzle pressure ratio (NPR)) being inlet aspect ratio (ARi) and length of the contraction section. The jet development was characterised using two parameters: location of the cross-over point (Xc) and the difference in the jet half-velocity widths along the major and minor axes (ΔB30). Based on the observed results, two statistical models were formulated for the prediction of axis-switching; the first model gives the location of the cross-over point, while the second model indicates the occurrence of axis-switching for the given configuration

Vortex annihilation in the ordering kinetics of the O(2) model

The vortex-vortex and vortex-antivortex correlation functions are determined for the two-dimensional O(2) model undergoing phase ordering. We find reasonably good agreement with simulation results for the vortex-vortex correlation function where there is a short-scaled distance depletion zone due to the repulsion of like-signed vortices. The vortex-antivortex correlation function agrees well with simulation results for intermediate and long-scaled distances. At short-scaled distances the simulations show a depletion zone not seen in the theory.Comment: 28 pages, REVTeX, submitted to Phys. Rev.