A simple calculation in the framework of the chiral quark theory of Manohar and Georgi yields results that can account for many of the “failures” of the naive quark model: significant strange quark content in the nucleon as indicated by the value of ${\sigma }_{\pi N}$, the $\overline{u}-\overline{d}$ a symmetry in the nucleon as measured by the deviation from the Gottfried sum rule and by the Drell-Yan process, as well as the various quark contributions to the nucleon spin as measured by deep inelastic polarized lepton-nucleon scattering.

• Received 13 October 1994

DOI:https://doi.org/10.1103/PhysRevLett.74.2872