arXiv subjects

C. A. Z. Vasconcellos

Publications and source records attributed to C. A. Z. Vasconcellos.

24 records · Page 2Linked to original sources

arXiv2006

Do glueballs contribute in heavy ion collisions?

In heavy ion collision simulations many hadron states and/or parton degrees of freedom are included in order to obtain the observables. Meson spectroscopy, for example, considers the $0^{++}$ meson as a mixture of $q\bar{q}$ and glue. This fact is usually not considered in heavy ion collision physics. In the present work we consider two extreme possibilities for the constitution of the $0^{++}$ meson, either as a pure glueball or as $q\bar{q}$-meson. The scattering amplitude and cross-sections with constituent interchange are determined for the two situations. The comparison showed that the glueball-glueball elastic scattering cross-section for a color singlet state is between one to two orders of magnitude smaller than the corresponding $q\bar{q}$ state. The $2^{++}$ glueball-glueball interaction is also evaluated with similar behavior. Thus, glueball-glueball scattering is not very likely to introduce significant changes in heavy ion collision observables.

hep-ph↗

arXiv2005

Glueball decay in the Fock-Tani formalism

We investigate the two-meson decay modes for $f_0(1500)$. In this calculation we consider this resonance as a glueball. The Fock-Tani formalism is introduced to calculate the decay width.

hep-ph↗

arXiv2005

Meson decay in the Fock-Tani Formalism

The Fock-Tani formalism is a first principle method to obtain effective interactions from microscopic Hamiltonians. Usually this formalism was applied to scattering, here we introduced it to calculate partial decay widths for mesons.

hep-ph↗

arXiv2004

Glueball-glueball scattering in a constituent gluon model

In this work we use a mapping technique to derive in the context of a constituent gluon model an effective Hamiltonian that involves explicit gluon degrees of freedom. We study glueballs with two gluons using the Fock-Tani formalism. In the present work we consider two possibilities for $0^{++}$: (i) as a pure $s\bar{s}$ and calculate, in the context of a quark interchange picture, the cross-section; (ii) as a glueball where a new calculation for this cross-section is made, in the context of the constituent gluon model, with gluon interchange.

hep-ph↗

arXiv2002

Phase Transitions in Neutron Stars and Gravitational Wave Emission

We review the detectability of gravitational waves generated by oscillations excited during a phase transition from hadronic matter to deconfined quark-gluon matter in the core of a neutron star. Neutron star properties were computed using a Boguta and Bodmer's based model and the MIT bag model. The maximum energy available to excite mechanical oscillations into the star is estimated by energy difference between the configurations with and without a quark-gluon matter core. On basis of the planned sensitivity of present laser interferometers (VIRGO or LIGO I) and those of the next generation (LIGO II), the maximum volume to be proped by these experiments is determined. These results are used as an indication of the potential detectability of neutron stars as sources of gravitational waves. Our results indicate that the maximum distance probed by the detectors of the first generation is well beyond M31, whereas the second generation detectors will probably see phase transitions events at distances two times longer, but certanly not yet attaining the Virgo cluster.

astro-ph↗

arXiv2000

Neutron stars in a class of non-linear relativistic models

We introduce in this work a class of relativistic models for nuclear matter and neutron stars which exhibits a parameterization, through mathematical constants, of the non-linear meson-baryon couplings. For appropriate choices of the parameters, it recovers current QHD models found in the literature: Walecka and the Zimanyi and Moszkowski models (ZM and ZM3). For other choices of the parameters, the new models give very interesting and new physical results.We have obtained numerical values for the maximum mass and radius of a neutron star sequence, red-shift, hyperon populations, radial distribution of particles, among other relevant static properties of these stellar objects. The phenomenology of neutron stars in ZM models is presented and compared to the phenomenology obtained in other versions of the Walecka model. We have found that the ZM3 model is too soft and predicts a very small maximum neutron star mass, $\sim0.72 M_\odot$. A strong similarity between the results of ZM-like models and those with exponential couplings is noted. Sensibility of the results to the specific choice of the values for the binding energy and saturation density is pointed out. Finally, we discuss the very intense scalar condensates found in the interior of neutron stars which may lead to negative effective masses.

nucl-th↗