771 research outputs found
and at low energies
We analyze the hadronization structure of decays. In the isospin limit only the vector current contributes to
this process. We compute the relevant form factor within Resonance Chiral
Theory, at leading order in the expansion, and considering only the
contribution of the lightest vector resonances. The couplings in the resonance
theory are constrained by imposing the asymptotic behaviour of vector spectral
functions ruled by . We reproduce the branching ratio of this mode and
predict the low-energy behaviour of
using isospin symmetry.Comment: 4 pages, 3 figures. To appear in the Proceedings of the QCD10 (25th
anniversary) 15th International QCD Conference. 28th June - 3rd July 2010
Montpellier (France) (Nucl. Phys. Proc. Suppl.
Improving the Hadronization of QCD currents in TAUOLA and PHOKHARA
We present our study of the hadronization structure of both vector and
axial-vector currents leading to decays of the tau into two kaons and a pion.
The cornerstones of our framework are the large-N_C limit of QCD, the chiral
structure exhibited at low energies and the proper asymptotic behaviour, ruled
by QCD, that is demanded to the associated form factors. The couplings of the
theory are mostly constrained by this procedure and upon the analysis of BaBar
data on e^+e^- -> KK pi we are able to predict the hadronic spectra.Comment: 4 pages, 1 figure. To appear in the Proceedings of QCD 08: 14th
International QCD Conference, 7-12th July 2008 Montpellier (France). To be
published by Elsevier in Nuclear Physics B (Proceedings Supplement
Phase diagram of neutron star quark matter in nonlocal chiral models
We analyze the phase diagram of two-flavor quark matter under neutron star
constraints for a nonlocal covariant quark model within the mean field
approximation. Applications to cold compact stars are discussed.Comment: 3 pages, 1 figure, proceedings of the IV International Conference on
Quarks and Nuclear Physics (QNP06), Madrid, Spain, June 5-10, 2006. To appear
in Eur. Phys. J.
Color neutrality effects in the phase diagram of the PNJL model
The phase diagram of a two-flavor Polyakov loop Nambu-Jona-Lasinio model is
analyzed imposing the constraint of color charge neutrality. Main effects of
this constraint are a shrinking of the chiral symmetry breaking (chiSB) domain
in the T-mu plane, a shift of the critical point to lower temperatures and a
coexistence of chiSB and two-flavor superconducting phases. The effects can be
understood in view of the presence of a nonvanishing color chemical potential
mu_8, which is necessary to compensate the color charge density rho_8 induced
by the nonvanishing Polyakov-loop mean field phi_3.Comment: 8 pages, 4 figures, figures added, minor text modification
Hadron structure in tau -> KKpi nu_tau decays
We analyse the hadronization structure of both vector and axial-vector
currents leading to tau -> KKpi nu_tau decays. At leading order in the 1/Nc
expansion, and considering only the contribution of the lightest resonances, we
work out, within the framework of the resonance chiral Lagrangian, the
structure of the local vertices involved in those processes. The couplings in
the resonance theory are constrained by imposing the asymptotic behaviour of
vector and axial-vector spectral functions ruled by QCD. In this way we predict
the hadron spectra and conclude that, contrarily to previous assertions, the
vector contribution dominates by far over the axial-vector one in all KKpi
charge channels.Comment: 32 pages, 7 figure
High resolution spectroscopy of symbiotic stars. VI. Orbital and stellar parameters for AR Pav
We present new dynamical parameters of the AR Pav binary system.
Ourobservations consist of a series of high resolution optical/NIR spectra from
which we derive the radial velocity curve of the red giant as well as its
rotation velocity. Assuming co-rotation, we determine the stellar radius (130
R_solar) of the red giant. Based on this we derive the red giant's luminosity
and mass (2.0 M_solar) as well as the distance of the system (4.9 kpc). The
binary mass function finally yields the companion's mass (0.75 M_solar) and the
binary separation (1.95 AU). We find that the red giant does not fill its Roche
lobe. We review the radial velocity data of Thackeray and Hutchings (1974), and
compare it with our red giant's orbit. We find that their RV curves of the blue
absorption system and the permitted emission lines are in anti-phase with the
red giant, and that the forbidden emission lines are shifted by a quarter of a
period. The blue absorptions and the permitted emission lines are associated
with the hot companion but not in a straightforward way. The blue absorption
system only tracks the hot component's orbital motion whilst it is in front of
the red giant, whereas at other phases line blanketing by interbinary material
leads to perturbations. We finally present UV light curves based on IUE archive
spectra. We clearly detect eclipses in the continuum at all wavelengths. The
eclipse light curves are unusual in that they show a slow and gradual decline
prior to eclipse which is followed by a sharp increase after eclipse.Comment: 9 pages, 5 figure
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