Measurement of the W+W- Production Cross Section in ppbar Collisions at sqrt(s)=1.96 TeV using Dilepton Events

We present a measurement of the W+W- production cross section using 184/pb of ppbar collisions at a center-of-mass energy of 1.96 TeV collected with the Collider Detector at Fermilab. Using the dilepton decay channel W+W- -> l+l-vvbar, where the charged leptons can be either electrons or muons, we find 17 candidate events compared to an expected background of 5.0+2.2-0.8 events. The resulting W+W- production cross section measurement of sigma(ppbar -> W+W-) = 14.6 +5.8 -5.1 (stat) +1.8 -3.0 (syst) +-0.9 (lum) pb agrees well with the Standard Model expectation.Comment: 8 pages, 2 figures, 2 tables. To be submitted to Physical Review Letter

International variation in phytosanitary legislation and regulations governing importation of plants for planting

The trade in plants for planting (P4P) is one of the major pathways for the introduction of pests. The strong increase in world trade in the past decades appears to have led to an increase in introductions of species transported by this pathway, and highlights the need for effective phytosanitary legislation and measures. The phytosanitary regulations in most countries are based on the International Plant Protection Convention and the World Trade Organisation's Agreement on Sanitary and Phytosanitary Measures, but there are large differences in countries' approaches to managing the risk of introducing invasive alien species through international plant trade. We reviewed elements of the phytosanitary legislations of ten countries on all continents and aimed to find regulations that prevent biological invasions. We found large differences in countries' phytosanitary regulations. New Zealand and Australia have the strictest phytosanitary regulations, while Europe maintains a general authorization for P4P imports. The remaining countries have regulations between these extremes. The evidence is sparse regarding the quality of implementation and effectiveness, and impact of individual phytosanitary measures. We recommend that National Plant Protection Organisations collect detailed information on P4P imports and the effectiveness of phytosanitary measures. Such information could provide a basis to improve a country's phytosanitary regulatory framework or could be used in risk assessments

Agricultural landscape structure and invasive species : The cost-effective level of crop field clustering

Invasive pests in agricultural settings may have severe consequences for agricultural production, reducing yields and the value of crops. Once an invader population has established, controlling it tends to be very expensive. Therefore, when the potential impacts on production may be great, protection against initial establishment is often perceived to be the most cost-effective measure. Increasing attention in the ecological literature is being given to the possibility of curbing invasion processes by manipulating the field and cropping patterns in agricultural landscapes, so that they are less conducive to the spread of pests. However, the economic implications of such interventions have received far less attention. This paper uses a stochastic spatial model to identify the key processes that influence the vulnerability of a fragmented agricultural landscape to pests. We explore the interaction between the divergent forces of ecological invasion pressure and economic returns to scale, in relation to the level of clustering of crop fields. Results show that the most cost-effective distances between crop fields in terms of reducing food production impacts from an invasive pest are determined by a delicate balance of these two forces and depend on the values of the ecological and economic parameters involved. If agricultural productivity declines slowly with increasing distance between fields and the dispersal range of the potential invader is high, manipulation of cropping structure has the potential to protect against invasion outbreaks and the farmer can gain benefit overall from maintaining greater distances between fields of similar crops

Central pseudorapidity gaps in events with a leading antiproton at the Fermilab tevatron pp collider

The results from a similar measurement performed in a subsample of pp events containing a leading (high longitudinal momentum) antiproton. As such, large pseudorapidity gaps are presumed to be due to Pomeron exchanges and are the signature for diffraction. The process with a leading beam particle in the final state, which is kinematically associated with an adjacent pseudorapidity gap, is known as single diffraction dissociation (SD), while that with a central gap as double diffraction dissociation (DD)

Search for long-lived charged massive particles in p p\u304 collisions at 1as = 1.8 TeV

A study was performed to search for long-lived charged massive particles in 90 pb-1 of data at CDF. No excess over background was observed. Cross section limits were observed using reference models for the two cases of strongly and weakly produced particles. In the strongly interacting case, these limits extend the excluded mass region to about 200 GeV/c2