12 research outputs found
Electron and Photon Scattering on Three-Nucleon Bound States
A big spectrum of processes induced by real and virtual photons on the 3He
and 3H nuclei is theoretically investigated through many examples based on
nonrelativistic Faddeev calculations for bound and continuum states. The modern
nucleon-nucleon potential AV18 together with the three-nucleon force UrbanaIX
is used. The single nucleon current is augmented by explicit pi- and rho-like
two-body currents which fulfill the current continuity equation together with
the corresponding parts of the AV18 potential. We also employ the Siegert
theorem, which induces many-body contributions to the current operator. The
interplay of these different dynamical ingredients in the various
electromagnetic processes is studied and the theory is compared to the
experimental data. Overall we find fair to good agreement but also cases of
strong disagreement between theory and experiment, which calls for improved
dynamics. In several cases we refer the reader to the work of other groups and
compare their results with ours. In addition we list a number of predictions
for observables in different processes which would challenge this dynamical
scenario even more stringently and systematically.Comment: 154 pages, 80 figures includes as ps files, 21 additional figures as
jpeg file
The Nucleon's Virtual Meson Cloud and Deep Inelastic Lepton Scattering
We address the question whether the nucleon's antiquark sea can be attributed
entirely to its virtual meson cloud and, in essence, whether there exists a
smooth transition between hadronic and quark-gluon degrees of freedom. We take
into account contributions from and mesons and compare with the
nucleon's antiquark distributions which serve as a non-perturbative input to
the QCD evolution equations. We elucidate the different behavior in the flavor
singlet and non-singlet channels and study the dependence of our results on the
scale . The meson-nucleon cut-offs that we determine give not only an
indication on the size of the region within which quarks are confined in a
nucleon, but we find that the scale of these form factors is closely related to
the four-momentum transfer, , where gluons are resolved by a high energy
probe, and that large meson loop momenta, GeV,
contribute significantly to the sea quark distributions. While the agreement of
our calculations with data-based parametrizations is satisfactory and scale
independent for the flavor breaking share of the nucleon's antiquark sea, the
flavor singlet component is quite poorly described. This hints the importance
of gluon degrees of freedom.Comment: 34 pages, RevTeX, 6 figures optionally included using epsfig.st
Elektromagnetische Eigenschaften des Dreinukleonengrundzustands
SIGLECopy held by FIZ Karlsruhe; available from UB/TIB Hannover / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman