Accurate nucleon electromagnetic form factors from dispersively improved chiral effective field theory

We present a theoretical parametrization of the nucleon electromagnetic form factors (FFs) based on a combination of chiral effective field theory and dispersion analysis. The isovector spectral functions on the two-pion cut are computed using elastic unitarity, chiral pion-nucleon amplitudes, and timelike pion FF data. Higher-mass isovector and isoscalar t-channel states are described by effective poles, whose strength is fixed by sum rules (charges, radii). Excellent agreement with the spacelike proton and neutron FF data is achieved up to Q^2 \sim 1 GeV^2. Our parametrization provides proper analyticity and theoretical uncertainty estimates and can be used for low-Q^2 FF studies and proton radius extraction.Comment: 5 pages, 3 figures, 2 table

On the \phi(1020)f_0(980) S-wave scattering and the Y(2175) resonance

We have studied the \phi(1020)f_0(980) S-wave scattering at energies around threshold employing chiral Lagrangians coupled to vector mesons through minimal coupling. The interaction kernel is obtained by considering the f_0(980) as a K\bar{K} bound state. The Y(2175) resonance is generated in this approach by the self-interactions between the \phi(1020) and the f_0(980) resonances. We are able to describe the e^+e^-\to \phi(1020)f_0(980) recent scattering data to test experimentally our scattering amplitudes, concluding that the Y(2175) resonance has a large \phi(1020)f_0(980) meson-meson component.Comment: 20 pages, 8 figure

Nuclear matter from the ladder resummation in terms of the experimental nucleon-nucleon scattering amplitudes

Infinite nuclear matter is studied by resuming the series of ladder diagrams based on the results developed by us in Ann. Phys. 437, 168741 (2022). The master formula for the energy density is explicitly solved for the case of contact interactions, within a pionless description of the nucleon-nucleon interactions. Renormalized results are obtained which are directly expressed in terms of the nucleon-nucleon phase shifts and mixing angles in partial-wave amplitudes up to an including $G$ waves, with convergence reached under the inclusion of higher partial waves. The energy per particle, density and sound velocity resulting from the ladder series are given for symmetric and neutron matter. This resummation of the ladder diagrams provides a rigorous result that may be used as low-density reference for other parameterizations of $\bar{\cal{E}}$ for higher densities.Comment: 29 pages, 9 figure