The Extended Chiral Quark Model in a Tamm-Dancoff Inspired Approximation

A procedure inspired by the Tamm-Dancoff method is applied to the chiral quark model which has been extended to include additional degrees of freedom: a pseudoscalar isoscalar field as well as a triplet of scalar isovector fields. The simpler, generic $\sigma$ -- model has been used before as a test for the Tamm-Dancoff inspired approximation (TDIA). The extended chirial quark model is employed here to investigate possible novel effects of the additional degrees of freedom as well as to point out the necessesity to introduce a SU(3) flavour. Model predictions for the axial-vector coupling constant and for the nucleon magnetic moment obtained in TDIA are compared with experimental values.Comment: 14 pages, LaTe

Teoretski opis hiperonskih nonleptonskih raspada

The theoretical description of the hyperon nonleptonic decays has been reexamined by using recently calculated next-to-leading QCD correlations.Ponovno je istražen teoretski opis hiperonskih nonleptonskih raspada upotrebljavajući nedavno izračunate QCD korekcije višeg reda. Suprotno no što je nađeno kod K → 2π raspada slaganje sa eksperimentom postane nešto lošije. Potrebno je ponovno ispitati teoretski pristup

Teoretski opis hiperonskih nonleptonskih raspada

The theoretical description of the hyperon nonleptonic decays has been reexamined by using recently calculated next-to-leading QCD correlations.Ponovno je istražen teoretski opis hiperonskih nonleptonskih raspada upotrebljavajući nedavno izračunate QCD korekcije višeg reda. Suprotno no što je nađeno kod K → 2π raspada slaganje sa eksperimentom postane nešto lošije. Potrebno je ponovno ispitati teoretski pristup

A non-hedgehog solution for the chiral bag

The chiral sigma model, embedded in the chiral-bag environment, is solved by an ansatz which conserves isospin and spin separably. This chiral ansatz is treated in two ways: i) as a set of operator equations of motion solved between quark states and ii) the hamilton operator is averaged between suitable hadron states, and the equations of motion are derived for these mean fields. The second approach is completely analogous to the usual one which employs hedgehog quarks, which is also reproduced here. It turns out that the energy minimum (i.e. hadron masses) can be found with chiral quarks as well as with hedgehog quarks. Model predictions for the axial-vector coupling constant and for the nucleon magnetic moment obtained with chiral quarks are of the same quality, or better than those obtained using the usual hedgehog-based approximation

Meson exchange formalism and the definition of delta functions

It is shown that in the simple context of the elementary one-meson exchanges, the use of the "improper" delta "functions" could lead to the physically correct results. The same results were obtained by involving limiting values of the integrals over "proper" functions, thus providing the examples of the sequences connected with delta "functions". That formulation of sequences of integrals emerged automatically from the physical considerations concerning hypernuclear processes

Vector mesonic phase and the chiral bag model

The mesonic sector of the standard chiral bag model was enlarged to include the vector and axial vector components. New model openly displays the current field identities. It's predictions are close to the older model. This seems to be the consequence of the chiral invariance and of the PCAC and CVC constraints. Particle masses, the axial-vector coupling constant, the proton magnetic moment and the charge radius have been calculated