A QCD sum rules calculation of the $J/psi D_s^* D_s$ strong coupling constant

In this work, we calculate the form factors and the coupling constant of the strange-charmed vertex $J/psi D_s^* D_s$ in the framework of the QCD sum rules by studying their three-point correlation functions. All the possible off-shell cases are considered, $D_s$, $D_s^*$ and $J/psi$, resulting in three different form factors. These form factors are extrapolated to the pole of their respective off-shell mesons, giving the same coupling constant for the process. Our final result for the $J/psi D_s^* D_s$ coupling constant is $g_{J/psi D^*_s D_s} = 4.30^{+0.42}_{-0.37}text{GeV}^{-1}$.

Obtaining the strong coupling constants g_{J/psi D_s D_s} and g_{phi D_s D_s} from QCD Sum Rules

The form factors and coupling constants of the meson vertices J/psi D_s D_s and phi D_s D_s were calculated using three point correlation functions within the QCD Sum Rules formalism. We have considered the cases where phi, D_s and J/psi mesons are off-shell obtaining, for each vertex, two different form factors and its corresponding coupling constants, namely g_{J/psi D_s D_s} = 6.20^{+0.97}_{-1.15} and g_{phi D_s D_s} = 1.85^{+0.22}_{-0.23}.

An inspection on the Borel masses relation used in QCD sum rules

In this work, we studied the Borel masses relation used in QCDSR calculations. These masses are the parameters of the Borel transform used when the three point function is calculated. We analised an usual and a more general linear relations. We concluded that a general linear relation between these masses provides the best results regarding the standard deviation.

Charm couplings and form factors in QCD sum rules

We review the calculations of form factors and coupling constants in vertices with charm mesons in the framework of QCD sum rules. We first discuss the motivation for this work, describing possible applications of these form factors to heavy ion collisions and to B decays. We then present an introduction to the method of QCD sum rules and describe how to work with the three-point function. We give special attention to the procedure employed to extrapolate results obtained in the deep euclidean region to the poles of the particles, located in the time-like region. We present a table of ready-to-use parametrizations of all the form factors, which are relevant for the processes mentioned in the introduction. We discuss the uncertainties in our results. We also give the coupling constants and compare them with estimates obtained with other methods. Finally we apply our results to the calculation of the cross section of the reaction $J/psi + pi rightarrow D + bar{D^*}$.

Hadron production in non linear relativistic mean field models

By using a parametrization of the non-linear Walecka model which takes into account the binding energy of different hyperons, we present a study of particle production yields measured in central Au-Au collision at RHIC. Two sets of different hyperon-meson coupling constants are employed in obtaining the hadron production and chemical freeze-out parameters. These quantities show a weak dependence on the used hyperon-meson couplings. Results are in good overall accordance with experimental data. We have found that the repulsion among the baryons is quite small and, through a preliminary analysis of the effective mesonic masses, we suggest a way to improve the fittings.

rho D^*D^* vertex from QCD sum rules

We calculate the form factors and the coupling constant in the $rho D^* D^*$ vertex in the framework of QCD sum rules. We evaluate the three point correlation functions of the vertex considering both $rho$ and $D^*$ mesons off--shell. The form factors obtained are very different but give the same coupling constant: $g_{rho D^* D^*} = 6.6 pm 0.31$. This number is 50% larger than what we would expect from SU(4) estimates.

Constraining relativistic models through heavy ion collisions

Relativistic models can be successfully applied to the description of compact star properties in nuclear astrophysics as well as to nuclear matter and finite nuclei properties, these studies taking place at low and moderate temperatures. Nevertheless, all results are model dependent and so far it is unclear whether some of them should be discarded. Moreover, in the regime of hot hadronic matter very few calculations exist using these relativistic models, in particular when applied to particle yields in heavy ion collisions. In the present work we comment on the known constraints that can help the selection of adequate models in this regime and investigate the main differences that arise when the particle production during a Au+Au collision at RHIC is calculated with different models.

$D^* D_s K$ and $D_s ^* D K$ vertices in a QCD Sum Rule approach

We calculate the strong form factors and coupling constants of $ D^* D_s K$ and $D_s^* D K$ vertices using the QCD sum rules technique. In each case we have considered two different cases for the off-shell particle in the vertex: the ligthest meson and one of the heavy mesons. The method gives the same coupling constant for each vertex. When the results for different vertices are compared, they show that the SU(4) symmetry is broken by around 40%.

J/psi D*D* vertex from QCD sum rules

We calculated the strong form factor and coupling constant for the $J/psi D^* D^*$ vertex in a QCD sum rule calculation. We performed a double Borel sum rule for the three point correlation function of vertex considering both $J/psi$ and $D^*$ mesons off--shell. The form factors obtained are very different, but they give the same coupling constant.

D and rho Mesons: Who resolves whom?

The DDrho form factor is evaluated in a QCD sum rule calculation for both D and rho off-shell mesons. We study the double Borel sum rule for the three point function of two pseudoscalar and one vector meson currents. We find that the momentum dependence of the form factors is very different if the D or the rho meson is off-shell, but they lead to the same coupling constant in the DDrho vertex. We discuss two different approaches to extract the DDrho coupling constant.