Chiral Bag Model Research Articles

A stable chiral bag model

A chiral bag model with an additional isoscalar (ω-meson) coupling is proposed. A mean field solution is found in the spherical approximation. We study the energy function and find that for strong enough isoscalar coupling the bag stabilizes.

Pion-nucleon scattering in the Chiral Bag Model

The effective hamiltonian of the πNΔ-system in the framework of the Chiral Bag Model (CBM) contains πNN-, πNΔ-, πΔΔ-interaction terms with a form factor which is essentially dependent on the size and shape of the quark bag. The iteration of the Born graphs of this model provides successful description of the (3,3) and (3,1) phase shifts [in the (3,3) resonance region] where the values of the parameters agree with the CBM.

The baryon masses and the chiral quark bag model

The baryon octet and decuplet mass spectrum is calculated within the chiral bag model. To zeroth order, this reduces to the MIT bag model. To the next order, baryon self-energies coming from coupling to pions enter. These are about as important as terms from gluon exchange; their inclusion decreases somewhat the colour coupling constant α s needed to fit the empirical baryon splittings. We show that mass splittings resulting from our calculation obey well the Gell-Mann-Okubo mass formulae, although certain terms included would individually violate them. Also the absolute value of the Λ magnetic moment comes out very well. In our theory, part of the mass splitting is a manifestation of the spontaneous breaking of chiral symmetry in the region outside the bag, resulting from the Goldstone pion which is introduced to conserve the axial current at the bag boundary. With inclusion of pionic interactions, the phenomenological zero-point energy introduced through the constant Z 0 in the MIT work is much smaller in order to fit the empirical masses, the pionic self-energies replacing most of it.

The Chiral bag and pion cloud contributions to the non relativistic quark model

Effects of the pion cloud in baryons predicted by Chiral Bag Models are studied by using a naive quark model approach.

Theσterm revisited

A standard analysis of the pion-nucleon $\ensuremath{\sigma}$ term uses partial conservation of the axial-vector current, current algebra, and a seemingly benign quark-model assumption and disagrees with experiment by a factor of 2. Here I calculate the $\ensuremath{\sigma}$ term in a hybrid chiral bag model and find that the discrepancy disappears. Excepting the $\ensuremath{\sigma}$ term the (successful) pattern of SU(3)- and SU(3) \ifmmode\times\else\texttimes\fi{} SU(3)-symmetry violation in the model is essentially identical to the more standard analysis.