The Feynman-Hellmann (FH) relation offers an alternative way of accessing hadronic matrix elements through artificial modifications to the QCD Lagrangian. In particular, a FH-motivated method provides a new approach to calculations of disconnected contributions to matrix elements and high-momentum nucleon and pion form factors. Here we present results for the total nucleon axial charge, including a statistically significant non-negative total disconnected quark contribution of around −5% at an unphysically heavy pion mass. Extending the FH relation to finite-momentum transfers, we also present calculations of the pion and nucleon electromagnetic form factors up to momentum transfers of around 7-8 GeV2. Results for the nucleon are not able to confirm the existence of a sign change for the ratio GMGE, but suggest that future calculations at lighter pion masses will provide fascinating insight into this behaviour at large momentum transfers.
@article{arxiv.1511.07090,
title = {Applications of the Feynman-Hellmann theorem in hadron structure},
author = {A. J. Chambers and R. Horsley and Y. Nakamura and H. Perlt and D. Pleiter and P. E. L. Rakow and G. Schierholz and A. Schiller and H. Stüben and R. D. Young and J. M. Zanotti},
journal= {arXiv preprint arXiv:1511.07090},
year = {2015}
}