Chiral pion dynamics for spherical bags

Thesis/Dissertation · Mon Dec 31 23:00:00 EST 1979

OSTI ID:5164747

Vento-Torres, V

We develop a phenomenological model for non-strange hadrons, based on the assumption that the strongly interacting particles are made up of quarks. The quarks are confined ad hoc, in a manner first introduced by the MIT group. Inside the confinement region (bag) the quarks interact via gluon-exchange. We introduce a pion field outside the bag, coupled to the quarks at the surface in such a way as to preserve chiral symmetry. We prove using the Goldberger-Treiman relation, that our pion field asymptotically coincides with the Yukawa field of a static distributed source. The pions contribute an attractive self-energy term to the mass of the hadron, which tends to reduce the size of the bag. The pion contribution breaks the SU(4) symmetry and thus distinguishes, e.g., between the nucleon and the isobar masses. Further, we develop a formalism for pion emission and absorption processes, whose main ingredient is the pion source term which appears as a consequence of the pion-quark coupling. We find good agreement with experiments for the ..delta.. decay into p..pi.. and for the rho decay into two ..pi..'s, if the bag has a radius of the order of 0.3 to 0.4 fm. We build a model for the electromagnetic form factors of the nucleon, in which the interaction with the meson cloud is described by vector meson dominance models. Again we find good agreement with experimental data for small cores of the order of 0.3 to 0.4 fm. In the last part of our work, we construct two chiral invariant models, a linear one with pion and sigma degrees of freedom, and a non-linear one with only pion degrees of freedom. Using the experimental ..pi..N coupling constant as an input we obtain masses for the baryons of the order of 1 GeV and pion decay constants of the order of 0.1 GeV for a variety of values of the radius.

• Research Organization: New York Univ., NY (USA)
• OSTI ID: 5164747
• Country of Publication: United States
• Language: English

Related Subjects

645204* -- High Energy Physics-- Particle Interactions & Properties-Theoretical-- Strong Interactions & Properties
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
BAG MODEL
BARYONS
BOSONS
CHIRAL SYMMETRY
COMPOSITE MODELS
CONFINEMENT
DECAY
ELECTROMAGNETIC FORM FACTORS
ELEMENTARY PARTICLES
EXTENDED PARTICLE MODEL
FERMIONS
FORM FACTORS
GLUONS
HADRONS
MASS
MATHEMATICAL MODELS
MESONS
NUCLEONS
PARTICLE DECAY
PARTICLE MODELS
PARTICLE PROPERTIES
PIONS
POSTULATED PARTICLES
PSEUDOSCALAR MESONS
QUARK MODEL
QUARKS
SYMMETRY
SYMMETRY BREAKING
VECTOR DOMINANCE MODEL