Probing quark-gluon interactions with transverse polarized scattering.

Area of Science:

• Nuclear Physics
• Particle Physics
• Quantum Chromodynamics (QCD)

Background:

• QCD matrix elements are crucial for understanding nucleon structure.
• Higher twist effects contribute to understanding quark-gluon interactions beyond leading-order approximations.
• Previous studies have explored sum rules in electron-nucleon and electron-nucleus scattering.

Purpose of the Study:

• To extract QCD matrix elements from experimental data.
• To investigate the significance of the higher twist matrix element d˜2.
• To examine the isospin dependence of higher twist effects and test sum rules.

Main Methods:

• Analysis of doubly polarized inelastic electron scattering data on nuclei.
• Extraction of QCD matrix elements, specifically d˜2 and a0.
• Application of the Burkhardt-Cottingham sum rule to assess isospin dependence.

Main Results:

• The higher twist matrix element d˜2, originating from quark-gluon interactions, was found to be unambiguously nonzero.
• An isospin dependence of higher twist effects was observed, contingent on the validity of the Burkhardt-Cottingham sum rule.
• The fundamental Bjorken sum rule, derived from the a0 matrix element, was satisfied at low momentum transfer.

Conclusions:

• Quark-gluon interactions play a significant, nonzero role in electron-nucleus scattering.
• Higher twist effects exhibit an isospin dependence, providing insights into nuclear structure.
• Experimental verification of the Bjorken sum rule at low momentum transfer supports theoretical predictions.