69,241 research outputs found
Heavy ion collisions at intermediate energies in a quark-gluon exchange framework
Heavy ion collisions at intermediate energies can be studied in the context
of the Vlasov-Uehling-Uhlenbeck (VUU) model. One of the main features in this
model is the nucleon-nucleon (NN) cross section in the collisional term. Quark
interchange plays a role in the NN interaction and its effect can be observed
in the cross section. We explore the possibility that quark interchange effects
can appear in observables at energies lower than RHIC.Comment: To appear in the Proceedings of VIII Hadron Physics 200
Meson decay in the Fock-Tani Formalism
The Fock-Tani formalism is a first principle method to obtain effective
interactions from microscopic Hamiltonians. Usually this formalism was applied
to scattering, here we introduced it to calculate partial decay widths for
mesons.Comment: Presented at HADRON05 XI. "International Conference on Hadron
Spectroscopy" Rio de Janeiro, Brazil, August 21 to 26, 200
Meson decay in a corrected model
Extensively applied to both light and heavy meson decay and standing as one
of the most successful strong decay models is the model, in which
pair production is the dominant mechanism. The pair production can
be obtained from the non-relativistic limit of a microscopic interaction
Hamiltonian involving Dirac quark fields. The evaluation of the decay amplitude
can be performed by a diagrammatic technique for drawing quark lines. In this
paper we use an alternative approach which consists in a mapping technique, the
Fock-Tani formalism, in order to obtain an effective Hamiltonian starting from
same microscopic interaction. An additional effect is manifest in this
formalism associated to the extended nature of mesons: bound-state corrections.
A corrected is obtained and applied, as an example, to
and decays.Comment: 3 figures. To appear in Physical Review
Dynamic radiation force of acoustic waves on solid elastic spheres
The present study concerns the dynamic radiation force on solid elastic
spheres exerted by a plane wave with two frequencies (bichromatic wave)
considering the nonlinearity of the fluid. Our approach is based on solving the
wave scattering for the sphere in the quasilinear approximation within the
preshock wave range. The dynamic radiation force is then obtained by
integrating the component of the momentum flux tensor at the difference of the
primary frequencies over the boundary of the sphere. Results reveal that
effects of the nonlinearity of the fluid plays a major role in dynamic
radiation force leading it to a parametric amplification regime. The developed
theory is used to calculate the dynamic radiation force on three different
solid spheres (aluminium, silver, and tungsten). Resonances are observed in the
spectrum of the force on the spheres. They have larger amplitude and better
shape than resonances present in static radiation force.Comment: 9 pages, 4 figures, to appear in Physical Review
Evaluation of a Pound Net Leader Designed to Reduce Sea Turtle Bycatch
Offshore pound net leaders in the southern portion of Chesapeake Bay in Virginia waters were documented to incidentally take protected loggerhead, Caretta caretta, and Kemp’s ridley, Lepidochelys kempii, sea turtles. Because of these losses, NOAA’s National Marine Fisheries Service (NMFS) in 2004 closed the area to offshore pound net leaders annually from 6 May to 15 July and initiated a study of an experimental leader design that replaced the top two-thirds of the traditional mesh panel leader with vertical ropes (0.95 cm) spaced 61 cm apart. This experimental leader was tested on four pound net sites on the eastern shore of Chesapeake Bay in 2004 and 2005. During the 2 trial periods, 21 loggerhead and Kemp’s ridley sea turtles were found interacting with the control leader and 1 leatherback turtle, Dermochelys coriacea, was found interacting with the experimental leader. Results of a negative binomial regression analysis comparing the two leader designs found the experimental leader significantly reduced sea turtle interactions (p=0.03).
Finfish were sampled from the pound nets in the study to assess finfish catch performance differences between the two leader designs. Although the conclusions from this element of the experiment are not robust, paired t-test and Wilcoxon signed rank test results determined no significant harvest weight difference between the two leaders. Kolmogorov-Smirnov tests did not reveal any substantive size selectivity differences between the two leaders
Meson production in two-photon interactions at energies available at CERN Large Hadron Collider
The meson production cross sections are estimated considering photon-photon
interactions in hadron - hadron collisions at CERN LHC energies. We consider a
large number of mesons with photon-photon partial decay width well constrained
by the experiment and some mesons which are currently considered as hadronic
molecule and glueball candidates. Our results demonstrate that the experimental
analysis of these states is feasible at CERN - LHC.Comment: 5 pages, 1 figure, 4 tables. Version published in Physical Review
- …