124 research outputs found
Light Fermion Mass Effects in e^+e^- -> 4 Fermions
We investigated the effect of the light fermion masses on cross sections for
e^+e^- into 4 fermions in the Fermion Loop scheme defined in hep-ph/9612260,
and approximations to it. The effects are found to be very small, except of
course in the collinear region of single W-boson production where the electron
mass acts as the cut-off.Comment: 8 pages, latex, 3 ps figs include
Unstable particles in One Loop Calculations
We present a gauge invariant way to compute one loop corrections to processes
involving the production and decay of unstable particles.Comment: 21 pages latex, <A
HREF=http://pss058.psi.ch/preprints/unstablefull.ps>ps file,
PSI-PR-93-22, REVISED. (Completely rewritten due to many complaints about the
unclear exposition.
The summer North Atlantic Oscillation in CMIP3 models and related uncertainties in projected summer drying in Europe
This paper discusses uncertainties in model projections of summer drying in the Euro-Mediterranean region related to errors and uncertainties in the simulation of the summer NAO (SNAO). The SNAO is the leading mode of summer SLP variability in the North Atlantic/European sector and modulates precipitation not only in the vicinity of the SLP dipole (northwest Europe) but also in the Mediterranean region. An analysis of CMIP3 models is conducted to determine the extent to which models reproduce the signature of the SNAO and its impact on precipitation and to assess the role of the SNAO in the projected precipitation reductions. Most models correctly simulate the spatial pattern of the SNAO and the dry anomalies in northwest Europe that accompany the positive phase. The models also capture the concurrent wet conditions in the Mediterranean, but the amplitude of this signal is too weak, especially in the east. This error is related to the poor simulation of the upper-level circulation response to a positive SNAO, namely the observed trough over the Balkans that creates potential instability and favors precipitation. The SNAO is generally projected to trend upwards in CMIP3 models, leading to a consistent signal of precipitation reduction in NW Europe, but the intensity of the trend varies greatly across models, resulting in large uncertainties in the magnitude of the projected drying. In the Mediterranean, because the simulated influence of the SNAO is too weak, no precipitation increase occurs even in the presence of a strong SNAO trend, reducing confidence in these projections
EEWW: a generator for including one-loop and leading photonic two-loop corrections
We describe a generator for the process including all
one-loop and leading log photonic two-loop contributions. It includes
polarization of the beam and bosons, and the possibility to study the
effect of anomalous couplings.Comment: 13 pages latex with 2 figures ps; also available as
http://pss058.psi.ch/preprints/eewwmc.ps; PSI-PR-94-16 (added two references
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Overstromingen in Malawi en Mozambique
In mid-January, Malawi and Mozambique were hit by heavy rainfall that caused major impact with hundreds dead and more than three hundred thousand displaced. A major international aid operation was set up by the United Nations and the International Red Cross to help the most affected. The question arises again and again how rare this extreme rainfall is and whether this is (partly) caused by climate change. We are working with an international group, including KNMI and the Red Cross Red Crescent Climate Center, to set up a system that can answer these kinds of questions. We will use the parts that have already been completed here to provide a partial answer to the above question and to provide insight into problems that we encounter in practice. (translated
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