10 research outputs found
Towards an effective field theory for vector mesons
The assumption that vector mesons dominate the interactions of hadrons with
electromagnetism (vector-meson dominance - VMD) provides an important
phenomenological concept. On the other hand, a clear microscopic derivation is
still missing and there are cases where VMD drastically fails, e.g. for the
omega transition form factor. In principle, effective field theories with their
systematic expansion and power counting could provide a tool to assess the
validity of VMD and more generally to describe the interactions of vector
mesons at low energies. Though the systematic development is still in an infant
stage we present here a Lagrangian for light pseudoscalar and vector mesons
which is inspired by ideas from effective field theories. The Lagrangian is
used to calculate electromagnetic meson form factors. It turns out that one can
reproduce both the successes of VMD concerning the pion form factors and the
deviations from VMD concerning the omega transition form factor.Comment: Talk presented at the 50th International Winter Meeting on Nuclear
Physics, 23-27 January 2012, Bormio (Italy
Transport-theoretical Description of Nuclear Reactions
In this review we first outline the basics of transport theory and its recent
generalization to off-shell transport. We then present in some detail the main
ingredients of any transport method using in particular the Giessen
Boltzmann-Uehling-Uhlenbeck (GiBUU) implementation of this theory as an
example. We discuss the potentials used, the ground state initialization and
the collision term, including the in-medium modifications of the latter. The
central part of this review covers applications of GiBUU to a wide class of
reactions, starting from pion-induced reactions over proton and antiproton
reactions on nuclei to heavy-ion collisions (up to about 30 AGeV). A major part
concerns also the description of photon-, electron- and neutrino-induced
reactions (in the energy range from a few 100 MeV to a few 100 GeV). For this
wide class of reactions GiBUU gives an excellent description with the same
physics input and the same code being used. We argue that GiBUU is an
indispensable tool for any investigation of nuclear reactions in which
final-state interactions play a role. Studies of pion-nucleus interactions,
nuclear fragmentation, heavy ion reactions, hyper nucleus formation,
hadronization, color transparency, electron-nucleus collisions and
neutrino-nucleus interactions are all possible applications of GiBUU and are
discussed in this article.Comment: 173 pages, review article. v2: Text-rearrangements in sects. 2 and 3
(as accepted for publication in Physics Reports