Covariant Momentum Projection of the Soliton Bag: Recoil Corrections to the Hadronic Masses

摘要

A central problem in calculations based on relativistic bags is that of projection onto an eigenstate of zero momentum and the subsequent covariant boosting of that state to a non-zero momentum eigenstate. We are here particularly concerned with relativistic bag models. The prototype of such models is the MIT bag model. Along with a number of derivative models, it shares the common feature of a surface boundary condition to confine the quarks. The Lagrangian contains coordinates which describe the surface, but the time derivatives of these coordinates do not appear. This complicates quantization which can, however, be accomplished through the techniques of Dirac constraints. It is important to work in a fully quantum mechanical framework. A model which fulfills that requirement, is covariant, and is tractable is the soliton bag model of Freidberg and Lee. This is a model for the low energy properties of QCD in which hadrons appear as solitons in a scalar field with quarks trapped inside the structures. The soliton model, for the present discussion, contains (massless) quarks interacting with a nonlinear scalar field sigma; the momentum operator conjugate to sigma is pi = sigma, and the two satisfy the usual canonical equal-time commutation reltions. 12 references. (ERA citation 10:022073)