0000000000850267
AUTHOR
Santiago Noguera Puchol
Nonlocal chiral quark models with wavefunction renormalization: sigma properties and \pi-\pi scattering parameters
We analyze the sigma meson mass and width together with the pion-pion scattering parameters in the context of non-local chiral quark models with wave-function renormalization (WFR). We consider both non-local interactions based on the frequently used exponential form factor, and on fits to the mass and renormalization functions obtained in lattice calculations. In the case of the sigma properties we obtain results which are less dependent on the parameterization than in the standard local NJL model, and which are in reasonable agreement with the recently reported empirical values. We also show that the inclusion of the WFR tend to improve the description of the $\pi-\pi$ scattering paramete…
D-0-(D-0)over-bar mixing in the weak-gauged U(4)(L)circle times U(4)(R) chiral Lagrangian model
The D-0- mixing is analyzed in a weak gauged U(4)(L) x U(4)(R) chiral lagrangian model where the electroweak interaction is introduced as a gauge theory over the meson degrees of freedom. This model allows a particular realization of the G.I.M. mechanism and then could be useful in the study of processes where G.I.M. suppression is effective. As a test of the model we have also analyzed the K-0- mixing. We find am, in good agreement with the experimental result and we show that the D-0- mixing is very much suppressed in agreement with previous estimates in the Heavy Quark expansion framework.
Enhancement effects in exclusive pi pi production in gamma* gamma scattering
The exclusive pi pi and rho pi production in hard gamma*gamma scattering in the forward kinematical region where the virtual photon is highly off-shell is studied using the gamma -> pi(-) Transition Distribution Amplitudes obtained in realistic models for the pion. For rho pi production we confirm the previous estimates before QCD evolution. Nevertheless. once evolution is taken into account this cross section grows one order of magnitude. In the case of pi pi production we have evaluated the cross section including the pion pole contribution. We observe that this contribution is responsible for an enhancement of two orders of magnitude with respect to the cross section evaluated without th…
ββ2ν decay in 48Ca
[EN] A schematic study of the bb2n decay of 48Ca is made in a shell-model approach. The emphasis is especially put on the role of the spin-orbit potential in relation with the contribution of other terms in the strong interaction. This is discussed with a particular attention to the behavior of these ones under the SU(4) symmetry. Different methods in calculating the transition amplitude are also looked at with the aim to determine their reliability and, eventually, why they do not work. Further aspects relative to the failure of the operator expansion method to reproduce the results of more elaborate calculations are examined.
A (p/E) calculations of strong pionic decays of baryons
Strong pionic decays of baryons are studied in a non-relativistic quark model framework via a convergent (p/E) expansion of the transition operator. Results are compared to the ones obtained within a more conventional (p/m) expansion.
Single spin asymmetry parameter from deeply virtual compton scattering of hadrons up to twist - three accuracy. 1. Pion case
The study of deeply virtual Compton scattering (DVCS) has shown that electromagnetic gauge invariance requires, to leading order, not only twist-two but additional twist-three contributions. We apply this analysis and, using the Ellis-Furmanski-Petronzio factorization scheme, compute the single- (electron) spin asymmetry arising in the collision of longitudinally polarized electrons with hadrons up to twist-3 accuracy. In order to simplify the kinematics we restrict the actual calculation to pions in the chiral limit. The process is described in terms of the generalized parton distribution functions which we obtain within a bag model framework.