61,174 research outputs found
Direct nucleonemission from hot and dense regions described in the hydrodynamical model of relativistic heavy ion collisions
The collision process is described by hydrodynamical equations. The escape of nucleons which do not take part in the thermal equilibrium is considered by including drain terms in these equations. The energy spectra of the escaped nucleons and of nucleons evaporated after the breakup of the fluid are compared. NUCLEAR REACTIONS Relativistic heavy ion reactions, nuclear hydrodynamics, nucleon spectra
Spin and pseudospin symmetries in the antinucleon spectrum of nuclei
Spin and pseudospin symmetries in the spectra of nucleons and antinucleons
are studied in a relativistic mean-field theory with scalar and vector
Woods-Saxon potentials, in which the strength of the latter is allowed to
change. We observe that, for nucleons and antinucleons, the spin symmetry is of
perturbative nature and it is almost an exact symmetry in the physical region
for antinucleons. The opposite situation is found in the pseudospin symmetry
case, which is better realized for nucleons than for antinucleons, but is of
dynamical nature and cannot be viewed in a perturbative way both for nucleons
and antinucleons. This is shown by computing the spin-orbit and
pseudospin-orbit couplings for selected spin and pseudospin partners in both
spectra.Comment: 8 figures, uses revtex 4.1 macro
Off-shell effects on particle production
We investigate the observable effects of off-shell propagation of nucleons in
heavy-ion collisions at SIS energies. Within a semi-classical BUU transport
model we find a strong enhancement of subthreshold particle production when
off-shell nucleons are propagated.Comment: 11 pages, 3 figure
Toy model of the Nucleon - Nucleon potential
We start from a system of six interacting constituent quarks and examine how
the picture of two nucleons can change when substructure of the nucleons are
taken into account.Comment: 9 pages, 6 figures, proceedings of the international conference
"Nuclear Structure and Related Topics
Classical Hadrodynamics: A New Approach to Ultrarelativistic Heavy-Ion Collisions
We discuss a new approach to ultrarelativistic heavy-ion collisions based on
classical hadrodynamics for extended nucleons, corresponding to nucleons of
finite size interacting with massive meson fields. This new theory provides a
natural covariant microscopic approach that includes automatically spacetime
nonlocality and retardation, nonequilibrium phenomena, interactions among all
nucleons and particle production. In the current version of our theory, we
consider extended unexcited nucleons interacting with massive neutral
scalar () and neutral vector () meson fields. The resulting
classical relativistic many-body equations of motion are solved numerically
without further approximation for soft nucleon-nucleon collisions at = 14.6, 30, 60, 100 and 200 GeV/ to yield the transverse momentum
imparted to the nucleons. For the future development of the theory, the
isovector pseudoscalar (, , ), isovector scalar
(, , ), isovector vector (, ,
) and neutral pseudoscalar () meson fields that are known to be
important from nucleon-nucleon scattering experiments should be incorporated.
In addition, the effects of quantum uncertainty on the equations of motion
should be included by use of techniques analogous to those used by Moniz and
Sharp for nonrelativistic quantum electrodynamics.Comment: 6 pages, LA-UR-94-217
Quark Asymmetries in Nucleons
We have developed a physical model for the non-perturbative x-shape of parton
density functions in the proton, based on Gaussian fluctuations in momenta, and
quantum fluctuations of the proton into meson-baryon pairs. The model describes
the proton structure function and gives a natural explanation of observed quark
asymmetries, such as the difference between the anti-up and anti-down sea quark
distributions and between the up and down valence distributions. We also find
an asymmetry in the momentum distribution of strange and anti-strange quarks in
the nucleon, large enough to reduce the NuTeV anomaly to a level which does not
give a significant indication of physics beyond the standard model.Comment: 4 pages, 5 figures. Talk given at DIS 2005, Madison, USA, April
27-May 1, 200
- …