262 research outputs found
Recent topics of mesic atoms and mesic nuclei -- mesic nuclei exist ?--
We study -meson production in nuclei to investigate the in-medium
modification of the -meson spectral function at finite density. We
consider (), () and () reactions to produce a
-meson inside the nucleus and evaluate the effects of the medium
modifications to reaction cross sections. The structures of the bound states,
-mesic nuclei, are also studied. For strong absorptive interaction cases,
we need to know the spectrum shape in a wide energy region to deduce the
properties of .Comment: Talk given at EXA08, Vienna, September 2008. To be published in the
Proceedings, Hyperfine Interactions. 6 pages, 6 figure
Quantum Hall States of Gluons in Quark Matter
We have recently shown that dense quark matter possesses a color
ferromagnetic phase in which a stable color magnetic field arises
spontaneously. This ferromagnetic state has been known to be Savvidy vacuum in
the vacuum sector. Although the Savvidy vacuum is unstable, the state is
stabilized in the quark matter. The stabilization is achieved by the formation
of quantum Hall states of gluons, that is, by the condensation of the gluon's
color charges transmitted from the quark matter. The phase is realized between
the hadronic phase and the color superconducting phase. After a review of
quantum Hall states of electrons in semiconductors, we discuss the properties
of quantum Hall states of gluons in quark matter in detail. Especially, we
evaluate the energy of the states as a function of the coupling constant. We
also analyze solutions of vortex excitations in the states and evaluate their
energies. We find that the states become unstable as the gauge coupling
constant becomes large, or the chemical potential of the quarks becomes small,
as expected. On the other hand, with the increase of the chemical potential,
the color superconducting state arises instead of the ferromagnetic state. We
also show that the quark matter produced by heavy ion collisions generates
observable strong magnetic field Gauss when it enters the
ferromagnetic phase.Comment: 11 pages, 2 figure
Model-independent study of the QCD sum rule for the pi NN coupling constant
We reinvestigate the QCD sum rule for the pi NN coupling constant, g,
starting from the vacuum-to-pion matrix element of the correlation function of
the interpolating fields of two nucleons. We study in detail the physical
content of the correlation function without referring to the effective theory.
We consider the invariant correlation functions by splitting the correlation
function into different Dirac structures. We show that the coefficients of the
double-pole terms are proportional to g but that the coefficients of the
single-pole terms are not determined by g. In the chiral limit the single-pole
terms as well as the continuum terms are ill defined in the dispersion
integral. Therefore, the use of naive QCD sum rules obtained from the invariant
correlation functions is not justified. A possible procedure to avoid this
difficulty is discussed.Comment: 20 pages, 2 figure
eta-prime nucleus optical potential and possible eta-prime bound states
Starting from a recent model of the eta'N interaction, we evaluate the
eta'-nucleus optical potential, including the contribution of lowest order in
density, t rho/2m_eta', together with the second order terms accounting for
eta' absorption by two nucleons. We also calculate the formation cross section
of the eta' bound states from (pi+,p) reactions on nuclei. The eta'-nucleus
potential suffers from uncertainties tied to the poorly known eta'N
interaction, which can be partially constrained by the experimental modulus of
the eta'N scattering length and/or the recently measured transparency ratios in
eta' nuclear photoproduction. Assuming an attractive interaction and taking the
claimed experimental value |a_eta'N| = 0.1 fm, we obtain a eta' optical
potential in nuclear matter at saturation density of V_eta' = -(8.7 + 1.8i)
MeV, not attractive enough to produce eta' bound states in light nuclei. Larger
values of the scattering length give rise to deeper optical potentials, with
moderate enough imaginary parts. For a value |a_eta'| = 0.3 fm, which can still
be considered to lie within the uncertainties of the experimental constraints,
the spectra of light and medium nuclei show clear structures associated to
eta'-nuclear bound states and to threshold enhancements in the unbound region.Comment: 11 pages, 4 figures, 2 table
eta-Nucleus interactions and in-medium properties of N*(1535) in chiral models
The properties of eta-nucleus interaction and their experimental consequences
are investigated with eta-nucleus optical potentials obtained by postulating
the N*(1535) dominance for eta-N system. The N*(1535) properties in nuclear
medium are evaluated by two kinds of chiral effective models based on distinct
pictures of N*(1535). We find that these two models provide qualitatively
different optical potentials of the eta meson, reflecting the in-medium
properties of N*(1535) in these models. In order to compare these models in
physical observables, we calculate spectra of (d,3He) reactions for the eta
mesic nucleus formation with various kinds of target nuclei. We show that the
(d,3He) spectra obtained in these models are significantly different and are
expected to be distinguishable in experiments.Comment: 24 pages, 8 figure
Level crossing of particle-hole and mesonic modes in eta mesic nuclei
We study eta meson properties in the infinite nuclear matter and in atomic
nuclei with an emphasis on effects of the eta coupling to
N*(1535)--nucleon-hole modes. The N*(1535) resonance, which dominates the
low-energy eta-nucleon scattering, can be seen as a chiral partner of the
nucleon. The change of the chiral mass gap between the N* and the nucleon in a
nuclear medium has an impact on the properties of the eta-nucleus system. If
the N*-nucleon mass gap decreases with a density increase (chiral symmetry
restoration) the calculations show the existence of the resonance state at the
energy about 60 MeV and two bound eta-nucleus states with the binding energies
about -80 MeV. These states can have strong effect on predicted cross sections
of the ^12C (gamma,p) ^11B reaction with eta-meson production.Comment: 22 pages, 12 figure
- …