Calculations of Higher Twist Distribution Functions in the MIT Bag Model

TL;DR

This work addresses the calculation of higher-twist distribution functions in deep-inelastic scattering using the MIT bag model. The authors compute all two-quark distributions up to twist-4 and enforce momentum conservation via a complete set of intermediate states and the Peierls-Yoccoz projection, then evolve twist-2 parts with GLAP and treat twist-3/4 with naive power counting, with a bag scale of $\mu \approx 0.4$ GeV. The nine resulting two-quark distributions at the bag scale feed into the nucleon structure functions, and the predictions for $G_{2}^{p}(x)$ and the twist-4 contribution to $F_{L}$ (via $R^{(4)}(x,Q^{2})$) agree reasonably with experimental data at moderate $Q^{2}$. Limitations include the absence of explicit gluon fields, no flavor dependence, neglect of four-quark and Sullivan contributions, and simplified evolution for higher twists; these point to clear directions for refinement, such as adding meson-cloud effects and flavor structure. Overall, the work provides a controlled quark-model framework that connects two-quark correlations to higher-twist observables and offers benchmarks for future improvements in twist-3/4 evolution and experimental tests.

Abstract

We calculate all twist-two, three and four parton distribution functions involving two quark correlations using the wavefunction of the MIT bag model. The distributions are evolved up to experimental scales and combined to give the various nucleon structure functions. Comparisons with recent experimental data on higher twist structure functions at moderate values of $Q^{2}$ give good agreement with the calculated structure functions.