470 research outputs found
Dispersion-theoretical analysis of the nucleon electromagnetic form factors: Inclusion of time-like data
We update a recent dispersion--theoretical fit to the nucleon electromagnetic
form factors by including the existing data in the time--like region. We show
that while the time--like data for the proton can be described consistently
with the existing world space--like data, this is not the case for the neutron.
Another measurement of the process is called for. We
furthermore sharpen the previous estimate of the separation between the
perturbative and the non--perturbative regime, which is characterized by a
scale parameter GeV.Comment: 7 pp, LaTeX, uses epsf, 2 figures in separate file, four data points
changed, slight changes in the fits, conclusions unchange
Nucleon form factors: From the space-like to the time-like region
I discuss how dispersion relations can be used to analyse the nucleon
electromagnetic form factors, with particular emphasis on the constraints from
unitarity and pQCD. Results for nucleon radii, vector-meson couplings, the
onset of pQCD and bounds on the strangeness form factors are presented. The em
form factors in the time-like region reveal some interesting physics which is
not yet understood in full detail. The need for a better data basis at low,
intermediate and large momentum transfer and also in the time-like region is
stressed.Comment: 11 pp, LaTeX, uses epsf and espcrc1.sty, 6 figures, invited talk,
DAPHCE 96, Frascati, November 1996, to appear in the proceedings (Nucl. Phys.
A
Cross-section measurements in the NOMAD experiment
The NOMAD experiment collected valuable neutrino data samples, matching both
the large statistics of massive calorimeters and the reconstruction quality of
bubble chambers. This paper describes the recent measurements of neutrino
cross-sections on carbon target. The approach followed for cross-section
modeling is also explained.Comment: Proceedings of the NuInt05 conference, Okayama September 200
Nucleon electromagnetic form factors and polarization observables in space-like and time-like regions
We perform a global analysis of the experimental data of the electromagnetic
nucleon form factors, in space-like and time-like regions. We give the
expressions of the observables in annihilation processes, such as , or , in terms of form factors. We discuss some
of the phenomenological models proposed in the literature for the space-like
region, and consider their analytical continuation to the time-like region.
After determining the parameters through a fit on the available data, we give
predictions for the observables which will be experimentally accessible with
large statistics, polarized annihilation reactions.Comment: 25 pages, 5 figures 7 table
Introduction to Smart Mobility
REACT EU - FEDER11. Sustainable cities and communitie
Prediction of Three-body Decay Rates
We predict the rates of the charmless three-body and
modes due to weak vector current contributions to be and , respectively. The basis is a
factorization approach of current produced nucleon pairs, together with an
isospin transformation that relates nucleon weak vector form factors to
electromagnetic form factors. Adding the axial vector current contribution, we
find and to be at
order. The three-body modes appear to dominate over the two-body modes such as
, .Comment: 5 pages, 4 figures. Version to appear in Phys. Lett.
SeaDataNet regional climatologies: an overview
In the frame of the SeaDataNet project, several regional climatologies for the temperature and salinity
are being developed by different groups. The data used for these climatologies are distributed by the
40 SeaDataNet data centers.
Such climatologies have several uses:
1. the detection of outliers by comparison of the in situ data with the climatological fields,
2. the the optimization of locations of new observations,
3. the initialization of numerical hydrodynamic models.
4. definition of a reference state to identify anomalies and to detect long-term climatic trends
Diva (Data Interpolating Variational Analysis) software is adapted to each region by taking into account
the geometrical characteristics (coastlines, bathymetry) and the distribution of data (correlation length,
signal-to-noise ratio, reference field). The regional climatologies treated in this work are:
- JRA5: North Atlantic
- JRA6: Mediterranean Sea
- JRA7: Baltic Sea
- JRA8: North Sea, Arctic Sea
Several examples of gridded fields are presented in this work. The validation of the different products
is carried out through a comparison with the last release of the widespread World Ocean Atlas 2005
Final NOMAD results on nu_mu->nu_tau and nu_e->nu_tau oscillations including a new search for nu_tau appearance using hadronic tau decays
Results from the nu_tau appearance search in a neutrino beam using the full
NOMAD data sample are reported. A new analysis unifies all the hadronic tau
decays, significantly improving the overall sensitivity of the experiment to
oscillations. The "blind analysis" of all topologies yields no evidence for an
oscillation signal. In the two-family oscillation scenario, this sets a 90%
C.L. allowed region in the sin^2(2theta)-Delta m^2 plane which includes
sin^2(2theta)<3.3 x 10^{-4} at large Delta m^2 and Delta m^2 < 0.7 eV^2/c^4 at
sin^2(2theta)=1. The corresponding contour in the nu_e->nu_tau oscillation
hypothesis results in sin^2(2theta)<1.5 x 10^{-2} at large Delta m^2 and Delta
m^2 < 5.9 eV^2/c^4 at sin^2(2theta)=1. We also derive limits on effective
couplings of the tau lepton to nu_mu or nu_e.Comment: 46 pages, 16 figures, Latex, to appear on Nucl. Phys.
Search for nu(mu)-->nu(e) Oscillations in the NOMAD Experiment
We present the results of a search for nu(mu)-->nu(e) oscillations in the
NOMAD experiment at CERN. The experiment looked for the appearance of nu(e) in
a predominantly nu(mu) wide-band neutrino beam at the CERN SPS. No evidence for
oscillations was found. The 90% confidence limits obtained are delta m^2 < 0.4
eV^2 for maximal mixing and sin^2(2theta) < 1.4x10^{-3} for large delta m^2.
This result excludes the LSND allowed region of oscillation parameters with
delta m^2 > 10 eV^2.Comment: 19 pages, 8 figures. Submitted to Phys. Lett.
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