9 research outputs found
Symmetries of degenerate center singularities of plane vector fields
Let be a closed unit -disk on the plane centered at the origin ,
and be a smooth vector field such that is a unique singular point of
and all other orbits of are simple closed curves wrapping once around
. Thus topologically is a "center" singularity. Let also
be the group of all diffeomorphisms of which preserve
orientation and orbits of . In arXiv:0907.0359 the author described the
homotopy type of under assumption that the -jet of at
is non-degenerate. In this paper degenerate case is considered. Under
additional "non-degeneracy assumptions" on the path components of
with respect to distinct weak topologies are described.Comment: 21 page, 3 figure
The Dirac form factor predicts the Pauli form factor in the Endpoint Model
We compute the momentum-transfer dependence of the proton Pauli form factor
in the endpoint overlap model. We find the model correctly reproduces
the scaling of the ratio of with the Dirac Form factor observed
at the Jefferson Laboratory. The calculation uses the leading-power, leading
twist Dirac structure of the quark light-cone wave function, and the same
endpoint dependence previously determined from the Dirac form factor .
There are no parameters and no adjustable functions in the endpoint model's
prediction for . The model's predicted ratio
is quite insensitive to the endpoint wave function, which explains why the
observed ratio scales like down to rather low momentum transfers. The
endpoint model appears to be the only comprehensive model consistent with all
form factor information as well as reproducing fixed-angle proton-proton
scattering at large momentum transfer. Any one of the processes is capable of
predicting the others.Comment: 12 pages, 3 figure
Beam-helicity and beam-charge asymmetries associated with deeply virtual Compton scattering on the unpolarised proton
Beam-helicity and beam-charge asymmetries in the hard exclusive
leptoproduction of real photons from an unpolarised hydrogen target by a 27.6
GeV lepton beam are extracted from the HERMES data set of 2006-2007 using a
missing-mass event selection technique. The asymmetry amplitudes extracted from
this data set are more precise than those extracted from the earlier data set
of 1996-2005 previously analysed in the same manner by HERMES. The results from
the two data sets are compatible with each other. Results from these combined
data sets are extracted and constitute the most precise asymmetry amplitude
measurements made in the HERMES kinematic region using a missing-mass event
selection technique.Comment: (minor changes only compared to arXiv version 1