2,094 research outputs found
Scattering lengths of Nambu-Goldstone bosons off mesons and dynamically generated heavy-light mesons
Recent lattice QCD simulations of the scattering lengths of Nambu-Goldstone
bosons off the mesons are studied using unitary chiral perturbation theory.
We show that the Lattice QCD data are better described in the covariant
formulation than in the heavy-meson formulation. The can be
dynamically generated from the coupled-channels interaction without
\textit{a priori} assumption of its existence. A new renormalization scheme is
proposed which manifestly satisfies chiral power counting rules and has
well-defined behavior in the infinite heavy-quark mass limit. Using this scheme
we predict the heavy-quark spin and flavor symmetry counterparts of the
.Comment: 22 pages, 5 figures; to appear in Physical Review
Thermodynamics of a three-flavor nonlocal Polyakov--Nambu--Jona-Lasinio model
The present work generalizes a nonlocal version of the Polyakov loop-extended
Nambu and Jona-Lasinio (PNJL) model to the case of three active quark flavors,
with inclusion of the axial U(1) anomaly. Gluon dynamics is incorporated
through a gluonic background field, expressed in terms of the Polyakov loop.
The thermodynamics of the nonlocal PNJL model accounts for both chiral and
deconfinement transitions. Our results obtained in mean-field approximation are
compared to lattice QCD results for quark flavors. Additional
pionic and kaonic contributions to the pressure are calculated in random phase
approximation. Finally, this nonlocal 3-flavor PNJL model is applied to the
finite density region of the QCD phase diagram. It is confirmed that the
existence and location of a critical point in this phase diagram depends
sensitively on the strength of the axial U(1) breaking interaction.Comment: 31 pages, 15 figures, minor changes compared to v
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
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
Variational calculations for K-few-nucleon systems
Deeply bound KNN, KNNN and KNNNN states are discussed. The effective force
exerted by the K meson on the nucleons is calculated with static nucleons. Next
the binding energies are obtained by solving the Schrodinger equation or by
variational calculations.
The dominant attraction comes from the S-wave Lambda(1405) and an additional
contribution is due to Sigma(1385). The latter state is formed at the nuclear
peripheries and absorbs a sizable piece of the binding energy. It also
generates new branches of quasi-bound states. The lowest binding energies based
on a phenomenological KN input fall into the 40-80 MeV range for KNN, 90-150
MeV for KNNN and 120-220 MeV for K-alpha systems. The uncertainties are due to
unknown KN interactions in the distant subthreshold energy region.Comment: 19 pages, 1 figur
Chiral Dynamics of Deeply Bound Pionic Atoms
We present and discuss a systematic calculation, based on two-loop chiral
perturbation theory, of the pion-nuclear s-wave optical potential. A proper
treatment of the explicit energy dependence of the off-shell pion self-energy
together with (electromagnetic) gauge invariance of the Klein-Gordon equation
turns out to be crucial. Accurate data for the binding energies and widths of
the 1s and 2p levels in pionic ^{205}Pb and ^{207}Pb are well reproduced, and
the notorious "missing repulsion" in the pion-nuclear s-wave optical potential
is accounted for. The connection with the in-medium change of the pion decay
constant is clarified.Comment: preprint ECT*-02-16, 4 pages, 3 figure
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