10 research outputs found
Nucleon form factors and spin content in a quark-diquark model with a pion cloud
We propose a new model of the nucleon in which quark-diquark configurations
immersed in a pion cloud are treated in a manner consistent with Poincar\'e
invariance. With suitably chosen parameters, the computations employing this
model reproduce the measured electromagnetic form factors and the quark-spin
contribution to the total nucleon angular momentum.Comment: 10 pages, 11 figure
Dressed-quarks and the Roper resonance
A Dyson-Schwinger equation calculation of the light hadron spectrum, which
correlates the masses of meson and baryon ground- and excited-states within a
single framework, produces a description of the Roper resonance that
corresponds closely with conclusions drawn recently by EBAC. Namely, the Roper
is a particular type of radial excitation of the nucleon's dressed-quark core
augmented by a material meson cloud component. There are, in addition, some
surprises.Comment: 4 pages, 3 figures. Contribution to the Proceedings of "NSTAR2011 -
The 8th International Workshop on the Physics of Excited Nucleons," Thomas
Jefferson National Accelerator Facility, Newport News, Virginia USA, 17-20
May 201
Completing the picture of the Roper resonance
We employ a continuum approach to the three valence-quark bound-state problem
in relativistic quantum field theory to predict a range of properties of the
proton's radial excitation and thereby unify them with those of numerous other
hadrons. Our analysis indicates that the nucleon's first radial excitation is
the Roper resonance. It consists of a core of three dressed-quarks, which
expresses its valence-quark content and whose charge radius is 80% larger than
the proton analogue. That core is complemented by a meson cloud, which reduces
the observed Roper mass by roughly 20%. The meson cloud materially affects
long-wavelength characteristics of the Roper electroproduction amplitudes but
the quark core is revealed to probes with .Comment: 6 pages, 3 figure