The spin content of the proton in the light-cone quark model without SU(3) flavour symmetry

Abstract

The authors argue that it is inappropriate to use SU(3) flavour symmetry in analysing the recent EMC measurement of the proton spin structure function and then present a light-cone, quark-proton model analysis without using SU(3). The nucleon is described as a bound state of three relativistic quarks on the light-cone. The constituent quarks have their own internal structure in terms of valence quarks, a quark-antiquark sea and gluons. The EMC result, taken in conjunction with the Bjorken sum rule, gives, separately, the valence quark and an effective sea contribution to the proton spin, demonstrating explicit cancellation of the valence and sea contributions.