1,744 research outputs found
Note on Shadowing and Diffraction in Deep-Inelastic Lepton Scattering
We discuss the close relation between shadowing in deep-inelastic
lepton-nucleus scattering and diffractive photo- and leptoproduction of hadrons
from free nucleons. We show that the magnitude of nuclear shadowing at small
Bjorken-x, as measured by the E665 and NMC collaborations, is directly related
to HERA data on the amount of diffraction in the scattering from free nucleons.Comment: 6 pages, Latex, to be published in Eur. Phys. J.
Lambda-nuclear interactions and hyperon puzzle in neutron stars
Brueckner theory is used to investigate the in-medium properties of a
-hyperon in nuclear and neutron matter, based on hyperon-nucleon
interactions derived within SU(3) chiral effective field theory (EFT). It is
shown that the resulting single-particle potential
becomes strongly repulsive for densities
of two-to-three times that of normal nuclear matter. Adding a density-dependent
effective -interaction constructed from chiral
three-body forces increases the repulsion further. Consequences of these
findings for neutron stars are discussed. It is argued that for hyperon-nuclear
interactions with properties such as those deduced from the SU(3) EFT
potentials, the onset for hyperon formation in the core of neutron stars is
expected to be shifted to extremely high baryon density, thus potentially
resolving the so-called hyperon puzzle.Comment: 6 pages, two figures; longer discussion about uncertainties adde
Microscopic optical potential from chiral nuclear forces
The energy- and density-dependent single-particle potential for nucleons is
constructed in a medium of infinite isospin-symmetric nuclear matter starting
from realistic nuclear interactions derived within the framework of chiral
effective field theory. The leading-order terms from both two- and
three-nucleon forces give rise to real, energy-independent contributions to the
nucleon self-energy. The Hartree-Fock contribution from the two-nucleon force
is attractive and strongly momentum dependent, in contrast to the contribution
from the three-nucleon force which provides a nearly constant repulsive mean
field that grows approximately linearly with the nuclear density. Together, the
leading-order perturbative contributions yield an attractive single-particle
potential that is however too weak compared to phenomenology. Second-order
contributions from two- and three-body forces then provide the additional
attraction required to reach the phenomenological depth. The imaginary part of
the optical potential, which is positive (negative) for momenta below (above)
the Fermi momentum, arises at second-order and is nearly inversion-symmetric
about the Fermi surface when two-nucleon interactions alone are present. The
imaginary part is strongly absorptive and requires the inclusion of an
effective mass correction as well as self-consistent single-particle energies
to attain qualitative agreement with phenomenology.Comment: 12 pages, 7 figures, added references, corrected typo
Hyperons in nuclear matter from SU(3) chiral effective field theory
Brueckner theory is used to investigate the properties of hyperons in nuclear
matter. The hyperon-nucleon interaction is taken from chiral effective field
theory at next-to-leading order with SU(3) symmetric low-energy constants.
Furthermore, the underlying nucleon-nucleon interaction is also derived within
chiral effective field theory. We present the single-particle potentials of
Lambda and Sigma hyperons in symmetric and asymmetric nuclear matter computed
with the continuous choice for intermediate spectra. The results are in good
agreement with the empirical information. In particular, our calculation gives
a repulsive Sigma-nuclear potential and a weak Lambda-nuclear spin-orbit force.Comment: 13 pages, 10 figures, 5 tables; v2: published version, minor change
Scattering of decuplet baryons in chiral effective field theory
A formalism for treating the scattering of decuplet baryons in chiral
effective field theory is developed. The minimal Lagrangian and potentials in
leading-order SU(3) chiral effective field theory for the interactions of octet
baryons () and decuplet baryons () for the transitions ,
, , , , and are provided. As an application of the formalism we compare
with results from lattice QCD simulations for and
scattering. Implications of our results pertinent to the quest for dibaryons
are discussed.Comment: 26 pages, 6 figures; minor corrections in the text, references adde
Kaonic hydrogen and K^- p scattering
Chiral SU(3) effective field theory in combination with a relativistic
coupled channels approach is used to perform a novel analysis of the strong
interaction shift and width in kaonic hydrogen in view of the new accurate DEAR
measurements. Questions of consistency with previous K^- p data are examined.
Coulomb and isospin breaking effects turn out to be important and are both
taken into account in this work.Comment: 4 pages, 4 figure
Vector-axialvector mixing from a chiral effective field theory at finite temperature
We study the vector-axialvector mixing in a hot medium and its evolution
toward the chiral phase transition using different symmetry restoration
scenarios based on the generalized hidden local symmetry framework. We show
that the presence of the meson reduces the vector spectral function
around meson mass and enhances it around meson mass. The coupling
strength of to and vanishes at the critical temperature due
to the degenerate - masses. This feature holds rigorously in the
chiral limit and still stays intact to good approximation for the physical pion
mass.Comment: v2:11 pages, 6 figures, reorganized and expanded the text, new plots
and references added, main result and conclusions unchange
- …