Model-independent determination of the strong phase difference between D0D^0 and Dˉ0→π+π−π+π−\bar{D}^0 \to\pi^+\pi^-\pi^+\pi^- amplitudes

For the first time, the strong phase difference between $D^0$ and $\bar{D}^0\to\pi^+\pi^-\pi^+\pi^-$ amplitudes is determined in bins of the decay phase space. The measurement uses $818\,\mathrm{pb}^{-1}$ of $e^+e^-$ collision data that is taken at the $\psi(3770)$ resonance and collected by the CLEO-c experiment. The measurement is important for the determination of the $C P$-violating phase $\gamma$ in $B^{\pm}\to D K^{\pm}$ (and similar) decays , where the $D$ meson (which represents a superposition of $D^0$ and $\bar{D}^0$) subsequently decays to $\pi^+\pi^-\pi^+\pi^-$. To obtain optimal sensitivity to $\gamma$, the phase space of the $D \to \pi^+\pi^-\pi^+\pi^-$ decay is divided into bins based on a recent amplitude model of the decay. Although an amplitude model is used to define the bins, the measurements obtained are model-independent. The $CP$-even fraction of the $D \to \pi^+\pi^-\pi^+\pi^-$ decay is determined to be $F_{+}^{4\pi} = 0.769 \pm 0.021 \pm 0.010$, where the uncertainties are statistical and systematic, respectively. Using simulated $B^{\pm}\to D K^{\pm}, D \to \pi^+\pi^-\pi^+\pi^-$ decays, it is estimated that by the end of the current LHC run, the LHCb experiment could determine $\gamma$ from this decay mode with an uncertainty of $(\pm10\pm7)^\circ$, where the first uncertainty is statistical based on estimated LHCb event yields, and the second is due to the uncertainties on the parameters determined in this paper

Hyperion Studies Of Crop Stress In Mexico

Satellite-based measurements of crop stress could provide much needed information for cropland management, especially in developing countries where other precision agriculture technologies are too expensive (Pierce and Nowak 1999; Robert 2002). For example, detection of areas that are nitrogen deficient or water stressed could guide fertilizer and water management decisions for all farmers within the swath of the satellite. Several approaches have been proposed to quantify canopy nutrient or water content based on spectral reflectance, most of which involve combinations of reflectance in the form of vegetation indices. While these indices are designed to maximize sensitivity to leaf chemistry, variations in other aspects of plant canopies may significantly impact remotely sensed reflectance. These confounding factors include variations in canopy structural properties (e.g., leaf area index, leaf angle distribution) as well as the extent of canopy cover, which determines the amount of exposed bare soil within a single pixel. In order to assess the utility of spectral indices for monitoring crop stress, it is therefore not only necessary to establish relationships at the leaf level, but also to test the relative importance of variations in other canopy attributes at the spatial scale of the remote sensing measurement. In this context, the relative importance of a given attribute will depend on (1) the sensitivity of the reflectance index to variation in the attribute and (2) the degree to which the attribute varies spatially and temporally

Liana canopy cover mapped throughout a tropical forest with high-fidelity imaging spectroscopy

Increasing size and abundance of lianas relative to trees are pervasive changes in Neotropical forests that may lead to reduced forest carbon stocks. Yet the liana growth form is chronically understudied in large-scale tropical forest censuses, resulting in few data on the scale, cause, and impact of increasing lianas. Satellite and airborne remote sensing provide potential tools to map and monitor lianas at much larger spatial and rapid temporal scales than are possible with plot-based forest censuses. We combined high-resolution airborne imaging spectroscopy and a ground-based tree canopy census to investigate whether tree canopies supporting lianas could be discriminated from tree canopies with no liana coverage. Using support vector machine algorithms, we achieved accuracies of nearly 90% in discriminating the presence–absence of lianas, and low error (15.7% RMSE) when predicting liana percent canopy cover. When applied to the full image of the study site, our model had a 4.1% false-positive error rate as validated against an independent plot-level dataset of liana canopy cover. Using the derived liana cover classification map, we show that 6.1%–10.2% of the 1823 ha study site has high-to-severe (50–100%) liana canopy cover. Given that levels of liana infestation are increasing in Neotropical forests and can result in high tree mortality, the extent of high-to-severe liana canopy cover across the landscape may have broad implications for ecosystem function and forest carbon storage. The ability to accurately map landscape-scale liana infestation is crucial to quantifying their effects on forest function and uncovering the mechanisms underlying their increase

New results for a photon-photon collider

We present new results from studies in progress on physics at a two-photon collider. We report on the sensitivity to top squark parameters of MSSM Higgs boson production in two-photon collisions; Higgs boson decay to two photons; radion production in models of warped extra dimensions; chargino pair production; sensitivity to the trilinear Higgs boson coupling; charged Higgs boson pair production; and we discuss the backgrounds produced by resolved photon-photon interactions

Improved timber harvest techniques maintain biodiversity in tropical forests

Tropical forests are selectively logged at 20 times the rate at which they are cleared, and at least a fifth have already been disturbed in this way. In a recent pan-tropical assessment, Burivalova et al. demonstrate the importance of logging intensity as a driver of biodiversity decline in timber estates. Their analyses reveal that species richness of some taxa could decline by 50% at harvest intensities of 38 m3 ha-1. However, they did not consider the extraction techniques that lead to these intensities. Here, we conduct a complementary meta-analysis of assemblage responses to differing logging practices: conventional logging and reduced-impact logging. We show that biodiversity impacts are markedly less severe in forests that utilise reduced-impact logging, compared to those using conventional methods. While supporting the initial findings of Burivalova et al., we go on to demonstrate that best practice forestry techniques curtail the effects of timber extraction regardless of intensity. Therefore, harvest intensities are not always indicative of actual disturbance levels resulting from logging. Accordingly, forest managers and conservationists should advocate practices that offer reduced collateral damage through best practice extraction methods, such as those used in reduced-impact logging. Large-scale implementation of this approach would lead to improved conservation values in the 4 million km2 of tropical forests that are earmarked for timber extraction