854 research outputs found
The hadronic off-shell width of meson resonances
Within the resonance chiral effective theory we study the dressed propagators
of the spin-1 fields, as arise from a Dyson-Schwinger resummation
perturbatively constructed from loop diagrams with absorptive contributions in
the s-channel. We apply the procedure to the vector pion form factor and the
elastic pion-pion scattering to obtain the off-shell width of the rho_0 meson.
We adopt a definition of the off-shell width of spin-1 meson resonances that
satisfies the requirements of analyticity, unitarity, chiral symmetry and
asymptotic behaviour ruled by QCD. To fulfil these constraints the resummation
procedure cannot consist only of self-energy diagrams. Our width definition is
shown to be independent of the formulation used to describe the spin-1 meson
resonances.Comment: 1+12 pages, 4 figures. Minor changes in text. Conclusions unchanged.
Version accepted for publication in Phys. Rev.
Deconfinement and chiral restoration in nonlocal SU(3) chiral quark models
We study the features of nonlocal SU(3) chiral quark models with wave
function renormalization. Model parameters are determined from meson
phenomenology, considering different nonlocal form factor shapes. In this
context we analyze the characteristics of the deconfinement and chiral
restoration transitions at finite temperature, introducing the couplings of
fermions to the Polyakov loop. We analyze the results obtained for various
thermodynamical quantities considering different Polyakov loop potentials and
nonlocal form factors, in comparison with data obtained from lattice QCD
calculations.Comment: 25 pages, 5 figures. Discussion of results enlarged, figures
modified, references added. Version to appear in Physical Review
Generalized Ginzburg-Landau approach to inhomogeneous phases in nonlocal chiral quark models
We analyze the presence of inhomogeneous phases in the QCD phase diagram
within the framework of nonlocal chiral quark models. We concentrate in
particular in the positions of the tricritical (TCP) and Lifshitz (LP) points,
which are studied in a general context using a generalized Ginzburg-Landau
approach. We find that for all the phenomenologically acceptable model
parametrizations considered the TCP is located at a higher temperature and a
lower chemical potential in comparison with the LP. Consequently, these models
seem to favor a scenario in which the onset of the first order transition
between homogeneous phases is not covered by an inhomogeneous, energetically
favored phase.Comment: 9 pages, 1 figure. V2: Two references added, figure modified, minor
changes in the text introduced. Matches version to be published in Physics
Letters
Inhomogeneous phases in nonlocal chiral quark models
The presence of inhomogeneous phases in the QCD phase diagram is analyzed
within chiral quark models that include nonlocal interactions. We work at the
mean field level, assuming that the spatial dependence of scalar and
pseudo-scalar condensates is given by a dual chiral density wave. Phase
diagrams for Gaussian nonlocal form factors are studied in detail and compared
with those obtained within the Nambu-Jona-Lasinio model and quark-meson
approaches.Comment: 14 pages, 3 figure
Electric polarizability of nuclei from a longitudinal sum rule
The nuclear electric polarizability is theoretically analyzed using a sum
rule derived from the longitudinal part of the forward Compton amplitude.
Beyond the leading dipole contribution, this approach leads to the presence of
potential-dependent terms that do not show up in previous analyses. The
significance of these new contributions is illustrated by performing an
explicit calculation for a proton-neutron system interacting via a separable
potential.Comment: 9 pages, revtex. Minor changes, two references added. To appear in
Nucl. Phys.
Form factors of radiative pion decays in nonlocal chiral quark models
We study the radiative pion decay pi+ -> e+ nu_e gamma within nonlocal chiral
quark models that include wave function renormalization. In this framework we
analyze the momentum dependence of the vector form factor F_V(q^2), and the
slope of the axial-vector form factor F_A(q^2) at threshold. Our results are
compared with available experimental information and with the predictions given
by the NJL model. In addition we calculate the low energy constants l_5 and
l_6, comparing our results with the values obtained in chiral perturbation
theory.Comment: 22 pages, 1 figure. arXiv admin note: substantial text overlap with
arXiv:1011.640
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