Calculation of proton spin-dependent structure functions in quark models

Spin-dependent structure functions [ital g][sub 1][sup [ital p]]([ital x]) and [ital g][sub 2][sup [ital p]]([ital x]) of the proton are calculated in the MIT bag model and in the color-dielectric model using the method of Signal and co-workers. Decomposition of [ital g][sub 2] into the twist-two and -three parts, according to Jaffe, has also been done. While characteristics of the quark wave functions in these models are clearly seen in the [ital x] dependence of [ital g][sub 1][sup [ital p]]([ital x]), the transverse part [ital g][sub 2][sup [ital p]]([ital x]) is rather insensitive to the models. By selecting out the twist-three part of [ital g][sub 2][sup [ital p]]([ital x]), however, the model dependence becomes evident. The color-dielectric model predicts quark distributions which are closer to the nonrelativistic quark model when compared with the MIT bag model.