Analytic Perturbation Theory: A New Approach to the Analytic Continuation of the Strong Coupling Constant αS\alpha_S into the Timelike Region

The renormalization group applied to perturbation theory is ordinarily used to define the running coupling constant in the spacelike region. However, to describe processes with timelike momenta transfers, it is important to have a self-consistent determination of the running coupling constant in the timelike region. The technique called analytic perturbation theory (APT) allows a consistent determination of this running coupling constant. The results are found to disagree significantly with those obtained in the standard perturbative approach. Comparison between the standard approach and APT is carried out to two loops, and threshold matching in APT is applied in the timelike region.Comment: 16 pages, REVTeX, 7 postscript figure

Vector Meson Photoproduction with an Effective Lagrangian in the Quark Model

A quark model approach to the photoproduction of vector mesons off nucleons is proposed. Its starting point is an effective Lagrangian of the interaction between the vector meson and the quarks inside the baryon, which generates the non-diffractive s- and u- channel resonance contributions. Additional t-channel $\pi^0$ and $\sigma$ exchanges are included for the $\omega$ and $\rho^0$ production respectively to account for the large diffractive behavior in the small $t$ region as suggested by Friman and Soyeur. The numerical results are presented for the $\omega$ and $\rho$ productions in four isospin channels with the same set of parameters, and they are in good agreement with the available data not only in $\omega$ and $\rho^0$ productions but also in the charged $\rho$ productions where the additional t-channel $\sigma$ exchange does not contribute so that it provides an important test to this approach. The investigation is also extended to the $\phi$ photoproduction, and the initial results show that the non-diffractive behavior of the $\phi$ productions in the large $t$ region can be described by the s- and u- channel contributions with significantly smaller coupling constants, which is consistent with the findings in the similar studies in the QHD framework. The numerical investigation has also shown that polarization observables are essential for identifying so-called "missing resonances".Comment: 36 pages, 10 PS figures, extended version of nucl-th/9711061 and nucl-th/9803021, submitted to PR

The Kaon-Photoproduction Of Nucleons In The Quark Model

In this paper, we develop a general framework to study the meson-photoproductions of nucleons in the chiral quark model. The S and U channel resonance contributions are expressed in terms of the Chew-Goldberger-Low-Nambu (CGLN) amplitudes. The kaon-photoproduction processes, $\gamma p\to K^+ \Lambda$, $\gamma p\to K^+ \Sigma^0$, and $\gamma p\to K^0\Sigma^+$, are calculated. The initial results show that the quark model provides a much improved description of the reaction mechanism for the kaon-photoproductions of the nucleon with less parameters than the traditional phenomenological approaches.Comment: 25 pages, 9 postscript figures can be obtained from the author

Post-Inflationary Reheating

We study a model for reheating that has been much investigated for parametric resonance, having a quartic interaction of the scalar inflaton with another scalar field. Attention is particularly on the quantum excitations of the inflaton field and the metric perturbation with a smooth transition from quantum to classical stochastic states, followed through from a specific inflation model to a state including a relativistic fluid. The scalar fields enter non-perturbatively but the metric enters perturbatively, and the validity of this latter is assessed. In this model our work seems to point the large scale curvature parameter changing.Comment: 25 pages, 6 figures. Coding error(misprint) corrected:figures and some conclusions change

The Ecological Impacts of Contaminated Sediment from Abandoned Metal Mines

Contains public sector information licensed under the Open Government Licence v3.0. The OGL requires that users acknowledge the information provider and/or source of the information with an attribution statement.Pollution from abandoned non-coal (i.e. metal) mines is a serious impediment to rivers meeting the water quality targets set out in River Basin Management Plans. Recent work has identified the mines most likely to be causing a significant environmental impact and hence where efforts to prevent pollution need to be focussed. Yet, it is not clear to what extent rivers, and the animal and plant life they support, are impacted by the legacy of past pollution still bound up in river sediments. Work will be undertaken to reduce toxic metals in mine waters before they enter the river. However, if riverbed sediments are already contaminated and affecting life in rivers, the planned clean-up of mine water sources may not result in recovery of ecological condition. A controlled laboratory experiment was undertaken where river invertebrates (mayfly larvae) from an uncontaminated site were incubated with contaminated riverbed sediment collected downstream of an abandoned metal mine. Concentrations of metals in the tissues of the mayflies increased over the duration of the incubation, particularly those metals that were in high concentrations in the sediment, i.e. cadmium, copper and zinc. As the sediment was the only substantial source of metals in the experiment, it is apparent that the contaminated riverbed sediment was acting as a source of bioavailable metals. It is likely that contaminated sediments, including riverbed sediment, will act as a source of bioavailable metals, at least to benthic organisms, even where mine drainage water is treated to reduce metal concentrations. Metal toxicity occurs when the rate of metal uptake into an organism exceeds the combined rates of excretion and physiological detoxification. Current tests of metal toxicity on biota typically do not match in scale (temporal, spatial and taxonomic range) with assessments of ecological quality undertaken for management, which raises questions regarding the adequacy of environmental limits based on laboratory testing. Existing data were compiled describing geochemistry of riverbed sediment and the Biological Quality Elements invertebrates, diatoms, macrophytes and fish, collected by the regulatory authorities to assess the condition of rivers. As toxic effects of trace metals were not expected at low concentrations, the biological response to sediment metal concentration was determined using a threshold model. Thresholds were found for biotic metrics based on species richness, but other metrics (diatom EQR, macrophyte EQR and invertebrate ASPT) displayed implausible positive relationships with sediment metal concentrations and should not be relied upon for classification of ecological status in waterbodies affected by mining. New data were collected from 20 spatially-independent river catchments in areas affected by metal mine facilities, including samples of the macroinvertebrate community, bioavailability of metals (assessed as metal concentrations in the body tissue of tolerant taxa), and sediment metal concentrations. There were strong correlations between sediment metal concentrations and measured bioavailability, particularly for copper and lead. Measurements of bioavailable metals were related to changes in taxon richness in the invertebrate samples. The data were used to develop a new biotic index (MetTol), which can be used to assess the extent of ecological damage from metal contamination using standard invertebrate monitoring data, and to construct dose response curves based on species sensitivities. A number of approaches were used to establish tolerable limits for sediment metal concentrations based on ecological data, and the results compared with existing Canadian sediment quality guidelines. The limits for copper derived from ecological data were most consistent with existing sediment guidelines. The limits for other metals (silver, arsenic, cadmium, nickel, lead and zinc) derived from ecological data were up to an order of magnitude above the Canadian interim sediment quality guidelines. These existing guidelines, based on toxicological data, may be too precautionary, and we suggest that guideline sediment concentrations based on ecological data may provide a more appropriate level of protection for the environment

OGLE-2009-BLG-092/MOA-2009-BLG-137: A Dramatic Repeating Event With the Second Perturbation Predicted by Real-Time Analysis

We report the result of the analysis of a dramatic repeating gravitational microlensing event OGLE-2009-BLG-092/MOA-2009-BLG-137, for which the light curve is characterized by two distinct peaks with perturbations near both peaks. We find that the event is produced by the passage of the source trajectory over the central perturbation regions associated with the individual components of a wide-separation binary. The event is special in the sense that the second perturbation, occurring $\sim 100$ days after the first, was predicted by the real-time analysis conducted after the first peak, demonstrating that real-time modeling can be routinely done for binary and planetary events. With the data obtained from follow-up observations covering the second peak, we are able to uniquely determine the physical parameters of the lens system. We find that the event occurred on a bulge clump giant and it was produced by a binary lens composed of a K and M-type main-sequence stars. The estimated masses of the binary components are $M_1=0.69 \pm 0.11\ M_\odot$ and $M_2=0.36\pm 0.06\ M_\odot$, respectively, and they are separated in projection by $r_\perp=10.9\pm 1.3\ {\rm AU}$. The measured distance to the lens is $D_{\rm L}=5.6 \pm 0.7\ {\rm kpc}$. We also detect the orbital motion of the lens system.Comment: 18 pages, 5 figures, 1 tabl

Characterizing Low-Mass Binaries From Observation of Long Time-scale Caustic-crossing Gravitational Microlensing Events

Despite astrophysical importance of binary star systems, detections are limited to those located in small ranges of separations, distances, and masses and thus it is necessary to use a variety of observational techniques for a complete view of stellar multiplicity across a broad range of physical parameters. In this paper, we report the detections and measurements of 2 binaries discovered from observations of microlensing events MOA-2011-BLG-090 and OGLE-2011-BLG-0417. Determinations of the binary masses are possible by simultaneously measuring the Einstein radius and the lens parallax. The measured masses of the binary components are 0.43 $M_{\odot}$ and 0.39 $M_{\odot}$ for MOA-2011-BLG-090 and 0.57 $M_{\odot}$ and 0.17 $M_{\odot}$ for OGLE-2011-BLG-0417 and thus both lens components of MOA-2011-BLG-090 and one component of OGLE-2011-BLG-0417 are M dwarfs, demonstrating the usefulness of microlensing in detecting binaries composed of low-mass components. From modeling of the light curves considering full Keplerian motion of the lens, we also measure the orbital parameters of the binaries. The blended light of OGLE-2011-BLG-0417 comes very likely from the lens itself, making it possible to check the microlensing orbital solution by follow-up radial-velocity observation. For both events, the caustic-crossing parts of the light curves, which are critical for determining the physical lens parameters, were resolved by high-cadence survey observations and thus it is expected that the number of microlensing binaries with measured physical parameters will increase in the future.Comment: 8 pages, 5 figures, 4 table

MOA-2011-BLG-293Lb: A test of pure survey microlensing planet detections

Because of the development of large-format, wide-field cameras, microlensing surveys are now able to monitor millions of stars with sufficient cadence to detect planets. These new discoveries will span the full range of significance levels including planetary signals too small to be distinguished from the noise. At present, we do not understand where the threshold is for detecting planets. MOA-2011-BLG-293Lb is the first planet to be published from the new surveys, and it also has substantial followup observations. This planet is robustly detected in survey+followup data (Delta chi^2 ~ 5400). The planet/host mass ratio is q=5.3+/- 0.2*10^{-3}. The best fit projected separation is s=0.548+/- 0.005 Einstein radii. However, due to the s-->s^{-1} degeneracy, projected separations of s^{-1} are only marginally disfavored at Delta chi^2=3. A Bayesian estimate of the host mass gives M_L = 0.43^{+0.27}_{-0.17} M_Sun, with a sharp upper limit of M_L < 1.2 M_Sun from upper limits on the lens flux. Hence, the planet mass is m_p=2.4^{+1.5}_{-0.9} M_Jup, and the physical projected separation is either r_perp = ~1.0 AU or r_perp = ~3.4 AU. We show that survey data alone predict this solution and are able to characterize the planet, but the Delta chi^2 is much smaller (Delta chi^2~500) than with the followup data. The Delta chi^2 for the survey data alone is smaller than for any other securely detected planet. This event suggests a means to probe the detection threshold, by analyzing a large sample of events like MOA-2011-BLG-293, which have both followup data and high cadence survey data, to provide a guide for the interpretation of pure survey microlensing data.Comment: 29 pages, 6 figures, Replaced 7/3/12 with the version accepted to Ap

Binary microlensing event OGLE-2009-BLG-020 gives a verifiable mass, distance and orbit predictions

We present the first example of binary microlensing for which the parameter measurements can be verified (or contradicted) by future Doppler observations. This test is made possible by a confluence of two relatively unusual circumstances. First, the binary lens is bright enough (I=15.6) to permit Doppler measurements. Second, we measure not only the usual 7 binary-lens parameters, but also the 'microlens parallax' (which yields the binary mass) and two components of the instantaneous orbital velocity. Thus we measure, effectively, 6 'Kepler+1' parameters (two instantaneous positions, two instantaneous velocities, the binary total mass, and the mass ratio). Since Doppler observations of the brighter binary component determine 5 Kepler parameters (period, velocity amplitude, eccentricity, phase, and position of periapsis), while the same spectroscopy yields the mass of the primary, the combined Doppler + microlensing observations would be overconstrained by 6 + (5 + 1) - (7 + 1) = 4 degrees of freedom. This makes possible an extremely strong test of the microlensing solution. We also introduce a uniform microlensing notation for single and binary lenses, we define conventions, summarize all known microlensing degeneracies and extend a set of parameters to describe full Keplerian motion of the binary lenses.Comment: 51 pages, 8 figures, 2 appendices. Submitted to ApJ. Fortran codes for Appendix B are attached to this astro-ph submission and are also available at http://www.astronomy.ohio-state.edu/~jskowron/OGLE-2009-BLG-020