86,712 research outputs found
The First Moments of Nucleon Generalized Parton Distributions
We extrapolate the first moments of the generalized parton distributions
using heavy baryon chiral perturbation theory. The calculation is based on the
one loop level with the finite range regularization. The description of the
lattice data is satisfactory and the extrapolated moments at physical pion mass
are consistent with the results obtained with dimensional regularization,
although the extrapolation in the momentum transfer to does show
sensitivity to form factor effects which lie outside the realm of chiral
perturbation theory. We discuss the significance of the results in the light of
modern experiments as well as QCD inspired models.Comment: 14 pages, 9 figure
Phase transition from hadronic matter to quark matter
We study the phase transition from nuclear matter to quark matter within the
SU(3) quark mean field model and NJL model. The SU(3) quark mean field model is
used to give the equation of state for nuclear matter, while the equation of
state for color superconducting quark matter is calculated within the NJL
model. It is found that at low temperature, the phase transition from nuclear
to color superconducting quark matter will take place when the density is of
order 2.5 - 5. At zero density, the quark phase will appear
when the temperature is larger than about 148 MeV. The phase transition from
nuclear matter to quark matter is always first order, whereas the transition
between color superconducting quark matter and normal quark matter is second
order.Comment: 18 pages, 11 figure
Quark structure and nuclear effective forces
We formulate the quark meson coupling model as a many-body effective
Hamiltonian. This leads naturally to the appearance of many-body forces. We
investigate the zero range limit of the model and compare its Hartree-Fock
Hamiltonian to that corresponding to the Skyrme effective force. By fixing the
three parameters of the model to reproduce the binding and symmetry energy of
nuclear matter, we find that it allows a very satisfactory interpretation of
the Skyrme force.Comment: 4 pages, 1tabl
Interplay of Spin and Orbital Angular Momentum in the Proton
We derive the consequences of the Myhrer-Thomas explanation of the proton
spin problem for the distribution of orbital angular momentum on the valence
and sea quarks. After QCD evolution these results are found to be in very good
agreement with both recent lattice QCD calculations and the experimental
constraints from Hermes and JLab
Liquid-gas phase transition in nuclear matter including strangeness
We apply the chiral SU(3) quark mean field model to study the properties of
strange hadronic matter at finite temperature. The liquid-gas phase transition
is studied as a function of the strangeness fraction. The pressure of the
system cannot remain constant during the phase transition, since there are two
independent conserved charges (baryon and strangeness number). In a range of
temperatures around 15 MeV (precise values depending on the model used) the
equation of state exhibits multiple bifurcates. The difference in the
strangeness fraction between the liquid and gas phases is small when they
coexist. The critical temperature of strange matter turns out to be a
non-trivial function of the strangeness fraction.Comment: 15 pages, 7 figure
Quarks in Finite Nuclei
We describe the development of a theoretical description of the structure of
finite nuclei based on a relativistic quark model of the structure of the bound
nucleons which interact through the (self-consistent) exchange of scalar and
vector mesons.Comment: Invited talks presented at the Joint Japan-Australian Workshop on
"Quarks, Hadrons and Nuclei", Adelaide, November 1995, to appear in
Australian Jounal of Physic
Pure sea-quark contributions to the magnetic form factors of baryons
We propose the pure sea-quark contributions to the magnetic form factors of
baryons, and , as priority
observables for the examination of sea-quark contributions to baryon structure,
both in present lattice QCD simulations and possible future experimental
measurement. , the -quark contribution to the magnetic form
factor of , and , the -quark contribution to the
magnetic form factor of , are similar to the strange quark
contribution to the magnetic form factor of the nucleon, but promise to be
larger by an order of magnitude. We explore the size of this quantity within
chiral effective field theory, including both octet and decuplet intermediate
states. The finite range regularization approach is applied to deal with
ultraviolet divergences. Drawing on an established connection between quenched
and full QCD, this approach makes it possible to predict the sea quark
contribution to the magnetic form factor purely from the meson loop. In the
familiar convention where the quark charge is set to unity . We find a value of , which is
about seven times larger than the strange magnetic moment of the nucleon found
in the same approach. Including quark charge factors, the -quark
contribution to the magnetic moment exceeds the strange quark
contribution to the nucleon magnetic moment by a factor of 14.Comment: 5 pages, 3 figures. arXiv admin note: text overlap with
arXiv:1312.337
Virtual Compton Scattering from the Proton and the Properties of Nucleon Excited States
We calculate the contributions to the generalized polarizabilities of
the proton in virtual Compton scattering. The following nucleon excitations are
included: , , , , ,
and . The relationship between nucleon
structure parameters, properties and the generalized polarizabilities of
the proton is illustrated.Comment: 13 pages of text (Latex) plus 4 figures (as uuencoded Z-compressed
.tar file created by csh script uufiles
- …