Long-Range Forces of QCD

We consider the scattering of two color dipoles (e.g., heavy quarkonium states) at low energy - a QCD analog of Van der Waals interaction. Even though the couplings of the dipoles to the gluon field can be described in perturbation theory, which leads to the potential proportional to (N_c^2-1)/R^{7}, at large distances R the interaction becomes totally non-perturbative. Low-energy QCD theorems are used to evaluate the leading long-distance contribution \sim (N_f^2-1)/(11N_c - 2N_f)^2 R^{-5/2} exp(-2 \mu R) (\mu is the Goldstone boson mass), which is shown to arise from the correlated two-boson exchange. The sum rule which relates the overall strength of the interaction to the energy density of QCD vacuum is derived. Surprisingly, we find that when the size of the dipoles shrinks to zero (the heavy quark limit in the case of quarkonia), the non-perturbative part of the interaction vanishes more slowly than the perturbative part as a consequence of scale anomaly. As an application, we evaluate elastic \pi J/\psi and \pi J/\psi \to \pi \psi' cross sections.Comment: 16pages, 9 eps figures; discussion extended, 2 new references added, to appear in Phys.Rev.

Evidence for virtual Compton scattering from the proton

In virtual Compton scattering an electron is scattered off a nucleon such that the nucleon emits a photon. We show that these events can be selected experimentally, and present the first evidence for virtual Compton scattering from the proton in data obtained at the Stanford Linear Accelerator Center. The angular and energy dependence of the data is well described by a calculation that includes the coherent sum of electron and proton radiation

Geomorphic histories for river and catchment management

10.1098/rsta.2011.0599Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences37019662240-226

Caesium-137 in Southeast Asia: Is there enough left for soil erosion and sediment redistribution studies?

10.1016/j.jseaes.2013.08.012Journal of Asian Earth Sciences77108-11

The natural denudation rate of the lowlands near the Ranger mine, Australia: A target for mine site rehabilitation

This paper provides a robust estimate of the total natural denudation rate for the area surrounding the Ranger uranium mine in the Northern Territory, Australia. This rate will be used to assess whether the final rehabilitated landform of the Ranger mine will denude at the natural rate after the landform has stabilized. The approach adopted was to compile and analyze all existing estimates of the total denudation rate. (including both physical erosion rates and solution losses) from areas near the mine site. Where available, solution losses are based on local measurements. These were used to adjust estimates for other local sites, where only physical erosion rates are available. Adjustments were based on a global relationship between physical erosion and solution loss rates. The adjusted total denudation rate estimates were shown to have no statistically significant relationship with the time over which they have been estimated (the averaging time, maximum period about 59,000 years), which suggests that they conform to mass flux equilibrium. This form of equilibrium implies an equivalence between inputs and outputs of sediment and solutes for which there is some evidence. Because the denudation rates are independent of averaging times, the long-term average total natural denudation rate can be calculated from all of the data, giving a value of 0.075 ± 0.013 mm year−1 (75 mm 1000 years−1, 75 m Ma−1). This value is almost twice the previously quoted rate of 0.04 ± 0.03 mm year−1 (40 ± 30 mm 1000 years−1), which was calculated from a mixture of physical erosion rates and the total denudation rates including some from large river catchments. The derivation of a revised denudation rate provides confidence that the revised value, based on all available data, is representative of the region; and is therefore an appropriate value with which to assess the success of the rehabilitation of a post-mining landform

Quantifying Sediment Sources in Lowlying Sugarcane Land: A Sediment Budget Approach.

The flood plain of the Herbert River basin is predominantly used for sugarcane cultivation. Although flood plains are generally considered depositional areas, high sediment concentrations have been observed in the water draining from cane land. Erosion control measures have reduced erosion from cane fields, but other landscape elements (e.g. drains) could still be important sediment sources. For this study the total sediment output from a cane area was gauged and the contribution of a range of landscape elements was quantified with traditional erosion measurement methods. A sediment budget is used to both present and check the measurement results. The study indicates that this tropical flood plain area is a net source of sediment. Sediment loss from the cultivated cane land was 3.9 t ha(-1) between I December 1999 and 31 May 2000