Probing quark-gluon interactions with transverse polarized scattering

Phys Rev Lett. 2010 Sep 3;105(10):101601. doi: 10.1103/PhysRevLett.105.101601. Epub 2010 Sep 2.


We have extracted QCD matrix elements from our data on doubly polarized inelastic scattering of electrons on nuclei. We find the higher twist matrix element d˜2, which arises strictly from quark-gluon interactions, to be unambiguously nonzero. The data also reveal an isospin dependence of higher twist effects if we assume that the Burkhardt-Cottingham sum rule is valid. The fundamental Bjorken sum rule obtained from the a0 matrix element is satisfied at our low momentum transfer.