1,238 research outputs found
Near threshold Lambda and Sigma production in pp collisions
A model calculation for the reactions and near their thresholds is presented. It is argued that the experimentally
observed strong suppression of production compared to
production at the same excess energy could be due to a destructive interference
between the and exchange contributions in the reaction . Predictions for and
are given.Comment: 3 pages, 1 figure, uses espcrc1.sty, contribution presented at the
16th International Conference on Few-Body Problems in Physics, Taipei,
Taiwan, 6-10 March 200
Future Dispute System Design: Ethical Imperatives, Millennial and Beyond
Published in cooperation with the American Bar Association Section of Dispute Resolutio
Baryon vector and axial content up to the 7Q component
We have used the light-cone formulation of Chiral-Quark Soliton Model to
investigate the vector and axial content of octet, decuplet and the
hypothetical antidecuplet in the flavor SU(3) symmetry limit. We have extended
previous works by computing the 7Q contribution to vector and axial charges for
the octet and antidecuplet but stayed at the 5Q sector for the decuplet where
the full computation needs much more time. As expected the 7Q component has a
weaker impact on the quantities but still changes them by a few percent. We
give also a detailed decomposition of those charges into flavor, valence quark,
sea quark and antiquark contributions. Many of them are of course not (yet)
measured or estimated and constitute then a theoretical estimation. Among the
different interesting observations made in this work are the explicit
quadrupole deformation of decuplet baryons due to the pion field and the sum of
quark spins larger than the pentaquark one.Comment: 34 pages, 7 figures and 17 tables, revised and more explicit versio
Metagenomic analysis of nitrogen and methane cycling in the Arabian Sea oxygen minimum zone
Oxygen minimum zones (OMZ) are areas in the global ocean where oxygen concentrations drop to below one percent. Low oxygen concentrations allow alternative respiration with nitrate and nitrite as electron acceptor to become prevalent in these areas, making them main contributors to oceanic nitrogen loss. The contribution of anammox and denitrification to nitrogen loss seems to vary in different OMZs. In the Arabian Sea, both processes were reported. Here, we performed a metagenomics study of the upper and core zone of the Arabian Sea OMZ, to provide a comprehensive overview of the genetic potential for nitrogen and methane cycling. We propose that aerobic ammonium oxidation is carried out by a diverse community of Thaumarchaeota in the upper zone of the OMZ, whereas a low diversity of Scalindua-like anammox bacteria contribute significantly to nitrogen loss in the core zone. Aerobic nitrite oxidation in the OMZ seems to be performed by Nitrospina spp. and a novel lineage of nitrite oxidizing organisms that is present in roughly equal abundance as Nitrospina. Dissimilatory nitrate reduction to ammonia (DNRA) can be carried out by yet unknown microorganisms harbouring a divergent nrfA gene. The metagenomes do not provide conclusive evidence for active methane cycling; however, a low abundance of novel alkane monooxygenase diversity was detected. Taken together, our approach confirmed the genomic potential for an active nitrogen cycle in the Arabian Sea and allowed detection of hitherto overlooked lineages of carbon and nitrogen cycle bacteria
Polarization phenomena in the reaction NN to NNpi near threshold
First calculations for spin-dependent observables of the reactions , and near threshold are presented,
employing the J\"ulich model for pion production. The influence of resonant
(via the excitation of the ) and non-resonant p-wave pion
production mechanisms on these observables is examined. For the reactions and nice agreement of our predictions with the
presently available data on spin correlation coefficents is observed whereas
for the description of the data is less satisfying.Comment: 10 pages, 4 figure
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