2 research outputs found
Hybrid and Conventional Mesons in the Flux Tube Model: Numerical Studies and their Phenomenological Implications
We present results from analytical and numerical studies of a flux tube model
of hybrid mesons. Our numerical results use a Hamiltonian Monte Carlo algorithm
and so improve on previous analytical treatments, which assumed small flux tube
oscillations and an adiabatic separation of quark and flux tube motion. We find
that the small oscillation approximation is inappropriate for typical hadrons
and that the hybrid mass is underestimated by the adiabatic approximation. For
physical parameters in the ``one-bead" flux tube model we estimate the lightest
hybrid masses ( states) to be 1.8-1.9~GeV for
hybrids, 2.1-2.2~GeV for and 4.1-4.2~GeV for . We also
determine masses of conventional mesons with to in this
model, and confirm good agreement with experimental -averaged multiplet
masses. Mass estimates are also given for hybrids with higher orbital and
flux-tube excitations. The gap from the lightest hybrid level () to the
first hybrid orbital excitation () is predicted to be ~GeV
for light quarks and ~GeV for . Both and
hybrid multiplets contain the exotics and ; in
addition the has a and the contains a . Hybrid
mesons with doubly-excited flux tubes are also considered. The implications of
our results for spectroscopy are discussed, with emphasis on charmonium
hybrids, which may be accessible at facilities such as BEPC, KEK, a Tau-Charm
Factory, and in production at hadron colliders.Comment: 39 pages of RevTex. Figures available via anonymous ftp at
ftp://compsci.cas.vanderbilt.edu/QSM/bcsfig1.ps and /QSM/bcsfig6.p
A Prototype Neural-network To Perform Early Warning in Nuclear-power-plant
The paper presents some results of research work in the field of artificial neural networks (ANN) applied to nuclear safety. It shows how a priori knowledge in the form of qualitative physical reasoning can provide a powerful basis for designing a set of ANN-based detection subsystems. In particular, it explains how each ANN is in charge of modelling a physical relationship between a set of state variables (thermal balance, mass balance, etc.) by trying to predict one particular variable from other ones; then, the residual signal, defined by the difference between the predicted value and the real one is used to decide whether abnormalities are present. As far as the decision logic is concerned, the paper describes how robustness can be improved by adequate filters on the residuals. The proposed approach is then validated on data coming from a fullscope simulator of one of the Belgian nuclear power units: the neural-based detection system is trained on ''normal'' scenarios and is able, after learning, to detect reliably and rapidly most of the incidental situations chosen as tests