Quark-binding string

A relativistic invariant extended model of hadrons is constructed. The finite region where quarks can move freely is a line in a three-dimensional space. Physically, the construction resembles that of the MIT bag and the SLAC bubble. In the absence of quarks, the model reduces to the relativistic massless-string model. We then solve explicitly the closed-string version where massless quarks move only in the clockwise direction. The resulting quantum system does not satisfy Lorentz algebra. However, this negative result indicates that for an open (or closed) string, the quantum system is consistent if there are 22 quark fields. A quark-confining string is also constructed and discussed. This is obtained as an improved version of the quark-binding string. It incorporates many physically desirable features.