Publications
Publication Information
| Title | Nucleon form factors in dispersively improved Chiral Effective Field Theory II: Electromagnetic form factors |
| Authors | Jose Manuel Alarcon, Christian Weiss |
| JLAB number | JLAB-THY-17-2568 |
| LANL number | arXiv:1710.06430 |
| Other number | DOE/OR/23177-4230 |
| Document Type(s) | (Journal Article) |
| Associated with EIC: | No |
| Supported by Jefferson Lab LDRD Funding: | No |
| Funding Source: | Nuclear Physics (NP) |
| Other Funding: | MINECO and FEDER, FPA2016-77313-P |
|
Journal Compiled for Physical Review C Volume 97 Page(s) 055203 Refereed | |
| Publication Abstract: | We study the nucleon electromagnetic form factors (EM FFs) using a recently developed method combining Chiral Effective Field Theory ($\chi$EFT) and dispersion analysis. The spectral functions on the two-pion cut at $t > 4 M_\pi^2$ are constructed using the elastic unitarity relation and an $N/D$ representation. $\chi$EFT is used to calculate the real unctions $J_\pm^1 (t) = f_\pm^1(t)/F_\pi(t)$ (ratios of the complex $\pi\pi \rightarrow N \bar N$ partial-wave amplitudes and the timelike pion FF), which are free of $\pi\pi$ rescattering. Rescattering effects are included through the empirical timelike pion FF $|F_\pi(t)|^2$. The method allows us to compute the isovector EM spectral functions up to $t \sim 1$ GeV$^2$ with controlled accuracy (LO, NLO, and partial N2LO). With the spectral functions we calculate the isovector nucleon EM FFs and their derivatives at $t = 0$ (EM radii, moments) using subtracted dispersion relations. We predict the values of higher FF derivatives with minimal uncertainties and explain their collective behavior. We estimate the individual proton and neutron FFs by adding an empirical parametrization of the isoscalar sector. Excellent agreement with the present low-$Q^2$ FF data is achieved up to $\sim$0.5 GeV$^2$ for $G_E$, and up to $\sim$0.2 GeV$^2$ for $G_M$. Our results can be used to guide the analysis of low-$Q^2$ elastic scattering data and the extraction of the proton charge radius. |
| Experiment Numbers: | other |
| Group: | THEORY CENTER |
| Document: | |
| DOI: | https://doi.org/10.1103/PhysRevC.97.055203 |
| Accepted Manuscript: | PhysRevC.97.pdf |
| Supporting Documents: | |
| Supporting Datasets: | |