Abstract
We describe a procedure for extracting momentum derivatives of nucleon matrix elements on the lattice directly at . This is based on the Rome method for computing momentum derivatives of quark propagators. We apply this procedure to extract the nucleon isovector magnetic moment and charge radius as well as the isovector induced pseudoscalar form factor at and the axial radius. For comparison, we also determine these quantities with the traditional approach of computing the corresponding form factors, i.e. and for the case of the vector current and and for the axial current, at multiple values followed by -expansion fits. We perform our calculations at the physical pion mass using a 2HEX-smeared Wilson-clover action. To control the effects of excited-state contamination, the calculations were done at three source-sink separations and the summation method was used. The derivative method produces results consistent with those from the traditional approach but with larger statistical uncertainties especially for the isovector charge and axial radii.
- Received 6 December 2017
DOI:https://doi.org/10.1103/PhysRevD.97.034504
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.
Published by the American Physical Society