NUCLEON RECURRENCES IN QUARK BAG MODELS
UMLAND, ERIC ALEXANDER
Doctor of Philosophy
The cloudy bag model introduces a fundamental scalar field taken to be the pion into the MIT bag Lagrangian so as to restore chiral invariance to the theory. One also acquires the capability of calculating pion-baryon interaction quantities such as decay widths and coupling constants. In this work we review the MIT and cloudy bag formalism. We calculate the (DELTA)(DELTA)(pi) coupling constant and show that it disagrees with the single experimental determination of f(,(DELTA)(DELTA)(pi)). We also investigate the N('*)(1470) in the context of the cloudy bag theory. We use gluonic and pionic self-energy terms to mix the two orthogonal SU(6) N('*) states. After correcting the masses for spurious center-of-mass motion we obtain excellent agreement with those found in Ayed's two level phase shift analysis of (pi)N scattering in the N('*) region. A calculation of N('*)(--->)N(pi) and N('*)(--->)(DELTA)(pi) partial widths is also in good agreement with those of Ayed. Finally, we show that the bag theory predicts the existence of 3 quark + 1 gluon bound states. There are two degenerate low-lying such states, with zeroth-order masses near those of the N('*) and with quantum numbers of the nucleon, which we call "gluonic nucleons" (N('G)). We discuss preliminary results of cloudy bag calculations of the N('G) decay widths into the N(pi) channel. These results indicate that after gluon and pion exchange effects split the two states, the lower mass N('G) would be invisible in a (pi)N scattering experiment while the higher state is a viable candidate for the P(,11)(1710) resonance.
Particle physics; Elementary particles; High energy physics