Angular Correlations in Top Quark Pair Production and Decay at Hadron Colliders

We show how to observe sizable angular correlations between the decay products of the top quark and those of the anti-top quark in top quark pair production and decay at hadron colliders. These correlations result from the large asymmetry in the rate for producing like-spin versus unlike-spin top quark pairs provided the appropriate spin axes are used. The effects of new physics at production or decay on these correlations are briefly discussed.Comment: 34 pages, revtex, including 12 uuencoded postscript figure

Highly-parallelized simulation of a pixelated LArTPC on a GPU

The rapid development of general-purpose computing on graphics processing units (GPGPU) is allowing the implementation of highly-parallelized Monte Carlo simulation chains for particle physics experiments. This technique is particularly suitable for the simulation of a pixelated charge readout for time projection chambers, given the large number of channels that this technology employs. Here we present the first implementation of a full microphysical simulator of a liquid argon time projection chamber (LArTPC) equipped with light readout and pixelated charge readout, developed for the DUNE Near Detector. The software is implemented with an end-to-end set of GPU-optimized algorithms. The algorithms have been written in Python and translated into CUDA kernels using Numba, a just-in-time compiler for a subset of Python and NumPy instructions. The GPU implementation achieves a speed up of four orders of magnitude compared with the equivalent CPU version. The simulation of the current induced on 10^3 pixels takes around 1 ms on the GPU, compared with approximately 10 s on the CPU. The results of the simulation are compared against data from a pixel-readout LArTPC prototype

Salinity control

Comments from C.R. Parke of Manjimup, on an article published in the Agricultural Memo, Department of Agriculture, Manjimup District Office, August 4, 1979, Bevan Kingdom, titled "Do you really need an interceptor bank?' The article discussed salinity problems in the area caused by waterlogging and evaporation which can be treated by drainage. Preventing waterlogging and reclaiming saline areas by installing interceptor banks may be successful, but other methods are a lot cheaper and as effective. C.R. Parke met Mr. Whittington at the Wisalts field day at Manjimup and Mr. Whittington said the area of land lost to production through salt scald in this area was so small that farmers would not be concerned with an overall interceptor system. Mr. Whittington also said that the matter for concern which must be affecting the productivity of many individual farms, was the level of salinity in streams and no doubt many dams. Mr. Whittington went on to say that interceptor banks could be planned so that the fresh rain water could be controlled and diverted around the area containing the accumulated salt to dams or streams. PLEASE NOTE: We are unable to provide a public view of this newspaper article as the copyright is held by the publisher of Western Farmer and Grazier. If you would like to obtain a copy of this newspaper article for research purposes, please ‘request a copy'. This article is part of the WISALTS (Whittington Interceptor Sustainable Agriculture Land Treatment Society Incorporated) Collection

Genetic analysis of porcine circovirus type 2 (PCV2) in Queensland, Australia

Objective: To determine the current porcine circovirus type 2 (PCV2) genotypes circulating in pigs in Queensland (QLD).Methods: The PCV2 infection status of pigs was determined by real-time PCR testing of 210 lymph nodes and 30 serum samples derived from 45 QLD farms. PCV2-positive samples from 22 pigs from 15 farms were subjected to conventional polymerase chain reaction (PCR) and sequencing of the full PCV2 genome. Phylogenetic analysis of 17 of these sequences in relation to published PCV2 sequences was then performed, and the genotypes were compared.Results: PCV2 DNA was detected in 95 lymph nodes and 15 serum samples. Phylogenetic analysis of 17 PCV2 sequences demonstrated that seven belonged to genotype PCV2b, two to PCV2d, one to PCV2f and seven to an "intermediate group" that clustered with PCV2d on the full genome analysis.Conclusion: This work confirms earlier studies reporting the presence of PCV2b in Australia. It is the first study to report that PCV2d and PCV2f are also present in this country. PCV2d is currently a fast-spreading genotype globally, with reported high virulence. The potential implications of these findings with respect to pathogenicity and vaccine efficacy require further investigation

Precession and Nutation of the Earth

International audiencePrecession and nutation of the Earth originate in the tidal forces exerted by the Moon, the Sun, and the planets on the equatorial bulge of the Earth. Discovered respectively in the 2nd century B.C. by Hipparcus and in the 18th century by Bradley, their existence and characteristics were deduced theoretically by Newton for the precession and by d'Alembert for the nutation. After a historical review we explain, both in an intuitive manner and by simple calculations, the gravitational origin and the main characteristics of the precession-nutation. Then we describe in detail two fundamental theories, one using the Lagrangian formalism, the other the Hamiltonian one. A large final part is devoted to successive improvements of the precession-nutation theory in the last decades, both when considering the Earth as a rigid body and when taking into account the small effects of non-rigidity