7,555 research outputs found
The , , , , and as dynamically generated states from vector meson - vector meson interaction
We report on some recent developments in understanding the nature of the
low-lying mesonic resonances , , ,
, and . In particular we show that these five
resonances can be dynamically generated from vector meson--vector meson
interaction in a coupled-channel unitary approach, which utilizes the
phenomenologically very successful hidden-gauge Lagrangians to produce the
interaction kernel between two vector mesons, which is then unitarized by the
Bethe-Salpeter-equation method. The data on the strong decay branching ratios,
total decay widths, and radiative decay widths of these five states, and on
related decay processes can all be well described by such an approach.
We also make predictions, compare them with the results of earlier studies, and
highlight observables that if measured can be used to distinguish different
pictures of these resonances.Comment: 9 pages; Invited talk at workshop CHIRAL'10, Valencia (Spain), June
21-24, 201
Genome Sequence of a Novel Archaeal Rudivirus Recovered from a Mexican Hot Spring
We report the consensus genome sequence of a novel GC-rich rudivirus, designated SMR1 (Sulfolobales Mexican rudivirus 1), assembled from a high-throughput sequenced environmental sample from a hot spring in Los Azufres National Park in western Mexico
Statistical distribution of elapsed times and distances of seismic events: the case of the Southern Spain seismic catalogue
International audienceSeveral empiric cumulative distributions of elapsed times and distances between seismic events occurred in the Southern Iberian Peninsula from 1985 to 2000 (data extracted from the seismic catalogue of the Andalusian Institute of Geophysics) are investigated. Elapsed times and distances between consecutive seismic events of the whole catalogue, taking into account threshold magnitudes of 2.5, 3.0, 3.5 and 4.0, and of five seismic crises, without distinguishing magnitudes, are investigated. Additionally, the series of distances and elapsed times from the main event to every aftershock are also analysed for the five seismic crises. Even though a power law is sometimes a satisfactory model for the cumulative distribution of elapsed times and distances between seismic events, in some cases a fit with a Weibull distribution for elapsed times performs better. It is worth of mention that, in the case of the seismic crises, the fit achieved by the power law is sometimes improved when it is combined with a logarithmic law. The results derived might be a contribution to a better representation of the seismic activity by means of models that could be based on random-walk processes
Chaotic scattering with direct processes: A generalization of Poisson's kernel for non-unitary scattering matrices
The problem of chaotic scattering in presence of direct processes or prompt
responses is mapped via a transformation to the case of scattering in absence
of such processes for non-unitary scattering matrices, \tilde S. In the absence
of prompt responses, \tilde S is uniformly distributed according to its
invariant measure in the space of \tilde S matrices with zero average, < \tilde
S > =0. In the presence of direct processes, the distribution of \tilde S is
non-uniform and it is characterized by the average (\neq 0). In
contrast to the case of unitary matrices S, where the invariant measures of S
for chaotic scattering with and without direct processes are related through
the well known Poisson kernel, here we show that for non-unitary scattering
matrices the invariant measures are related by the Poisson kernel squared. Our
results are relevant to situations where flux conservation is not satisfied.
For example, transport experiments in chaotic systems, where gains or losses
are present, like microwave chaotic cavities or graphs, and acoustic or elastic
resonators.Comment: Added two appendices and references. Corrected typo
New Physics effects in the flavor-changing neutral couplings of the Top quark
We survey the flavor-changing neutral couplings (FCNC) of the top quark
predicted by some extensions of the Standard Model: THDM, SUSY, L-R symmetric,
TC2, 331, and models with extra quarks. Since the expected sensitivity of the
LHC and ILC for the tcV (V=\gamma,g,Z) and tcH couplings is of order of a few
percent, we emphasize the importance of any new physics effect that gives a
prediction for these FCNC couplings within this limit. We also review the
constraints imposed on these couplings from low-energy precision measurements.Comment: 19 pages, 7 figures. Accepted as a review paper in Int. J. of Mod.
Phys.
A sol-gel method for growing superconducting MgB2 films
In this paper we report a new sol-gel method for the fabrication of MgB2
films. Polycrystalline MgB2 films were prepared by spin-coating a precursor
solution of Mg(BH_4)_2 diethyl ether on (001)Al2O3 substrates followed with
annealing in Mg vapor. In comparison with the MgB2 films grown by other
techniques, our films show medium qualities including a superconducting
transition temperature of Tc ~ 37 K, a critical current density of Jc(5 K, 0 T)
~ 5 {\times} 10^6 A cm^{-2}, and a critical field of H_{c2}(0) ~ 19 T. Such a
sol-gel technique shows potential in the commercial fabrication of practically
used MgB2 films as well as MgB2 wires and tapes.Comment: 8 pages, 5 figure
Dipolar ordering in Fe8?
We show that the low-temperature physics of molecular nanomagnets, contrary
to the prevailing one-molecule picture, must be determined by the long-range
magnetic ordering due to many-body dipolar interactions. The calculations here
performed, using Ewald's summation, suggest a ferromagnetic ground state with a
Curie temperature of about 130 mK. The energy of this state is quite close to
those of an antiferromagnetic state and to a glass of frozen spin chains. The
latter may be realized at finite temperature due to its high entropy.Comment: 7 pages, no figures, submitted to EP
Intercomparison of spectroradiometers and Sun photometers for the determination of the aerosol optical depth during the VELETA-2002 field campaign
[ 1] In July 2002 the VELETA-2002 field campaign was held in Sierra Nevada ( Granada) in the south of Spain. The main objectives of this field campaign were the study of the influence of elevation and atmospheric aerosols on measured UV radiation. In the first stage of the field campaign, a common calibration and intercomparison between Licor-1800 spectroradiometers and Cimel-318 Sun photometers was performed in order to assess the quality of the measurements from the whole campaign. The intercomparison of the Licor spectroradiometers showed, for both direct and global irradiances, that when the comparisons were restricted to the visible part of the spectrum the deviations were within the instruments' nominal accuracies which allows us to rely on these instruments for measuring physical properties of aerosols at the different measurement stations. A simultaneous calibration on AOD data was performed for the Cimel-318 Sun photometers. When a common calibration and methodology was applied, the deviation was lowered to much less than 0.01 for AOD. At the same time an intercomparison has been made between the AOD values given by the spectroradiometers and the Sun photometers, with deviations obtained from 0.01 to 0.03 for the AOD in the visible range, depending on the channel. In the UVA range, the AOD uncertainty was estimated to be around 0.02 and 0.05 for Cimel and Licor respectively. In general the experimental differences were in agreement with this uncertainty estimation. In the UVB range the AOD measurements should not be used due to maximum instrumental uncertainties
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