22,857 research outputs found
production in the reaction
We discuss the mechanisms that lead to production in the
reaction. The problem has gained renewed interest
after different works converge to the conclusion that there are two resonances
around the region of 1400 MeV, rather than one, and that they couple
differently to the and channels. We look at the dynamics
of that reaction and find two mechanisms which eventually filter each one of
the resonances, leading to very different shapes of the invariant
mass distributions. The combination of the two mechanisms leads to a shape of
this distribution compatible with the experimental measurements.Comment: RevTeX4, 10 pages, 8 figures, 2 tables, Version to appear in Phys.
Rev.
Latest results for the antikaon-nucleon optical potential
The key question of this letter is whether the K-nucleus optical potential is
deep, as it is prefered by the phenomenological fits to kaonic atoms data, or
shallow, as it comes out from unitary chiral model calculations. The current
experimental situation is reviewed.Comment: 3 pages, 1 figure. Presented at the 21st European Conference on the
Few-Body problems in Physics (EFB21), Salamanca, Spain, August 29 - September
3, 201
FarNet-II: An improved solar far-side active region detection method
Context. Activity on the far side of the Sun is routinely studied through the
analysis of the seismic oscillations detected on the near side using
helioseismic techniques such as phase shift sensitive holography. Recently, the
neural network FarNet was developed to improve these detections. Aims. We aim
to create a new machine learning tool, FarNet II, which further increases the
scope of FarNet, and to evaluate its performance in comparison to FarNet and
the standard helioseismic method for detecting far side activity. Methods. We
developed FarNet II, a neural network that retains some of the general
characteristics of FarNet but improves the detections in general, as well as
the temporal coherence among successive predictions. The main novelties are the
implementation of attention and convolutional long short term memory (ConvLSTM)
modules. A cross validation approach, training the network 37 times with a
different validation set for each run, was employed to leverage the limited
amount of data available. We evaluate the performance of FarNet II using three
years of extreme ultraviolet observations of the far side of the Sun acquired
with the Solar Terrestrial Relations Observatory (STEREO) as a proxy of
activity. The results from FarNet II were compared with those obtained from
FarNet and the standard helioseismic method using the Dice coefficient as a
metric. Results. FarNet II achieves a Dice coefficient that improves that of
FarNet by over 0.2 points for every output position on the sequences from the
evaluation dates. Its improvement over FarNet is higher than that of FarNet
over the standard method. Conclusions. The new network is a very promising tool
for improving the detection of activity on the far side of the Sun given by
pure helioseismic techniques. Space weather forecasts can potentially benefit
from the higher sensitivity provided by this novel method.Comment: Accepted for publication in Astronomy and Astrophysics. Abridged
abstrac
Crossover of thermal to shot noise in chaotic cavities
We study the crossover between thermal and shot-noise power in a chaotic
quantum dot in the presence of non-ideal contacts at finite temperature. The
result explicitly demonstrates that the temperature affect the
suppression-amplification effect present in the main quantum noise. In
particular, the weak localization contribution to the noise has an anomalous
thermal behavior when one let the barriers vary, indicating the presence of a
critical point related to specific value of the tunneling barriers. We also
show how to get to the opaque limit of the quantum dot at finite temperature.Comment: 6 pages, 5 figures. To be published in Europhysics Letter
- …