Nucleon radius effects on neutron stars in quark mean field model

TL;DR

This study investigates how the free space nucleon radius influences nuclear matter and neutron star properties within a quark mean field model, finding negligible effects on the equation of state and star mass-radius relations.

Contribution

It introduces a self-consistent treatment of nucleon radius in the quark mean field model and clarifies the role of symmetry energy in star radius sensitivity.

Findings

Nucleon radius has negligible effect on nuclear matter EOS.

Neutron star mass-radius relations are insensitive to nucleon radius.

Star radius sensitivity is mainly due to symmetry energy and its slope.

Abstract

We study the effects of free space nucleon radius on nuclear matter and neutron stars within the framework of quark mean field model. The nucleon radius is treated self-consistently with this model, where quark confinement is adjusted to fit different values of nucleon radius. Corrections due to center-of-mass motion, quark-pion coupling, and one gluon exchange are included to obtain the nucleon mass in vacuum. The meson coupling constants that describe the behavior of many-body nucleonic system are newly-constructed by reproducing the empirical saturation properties of nuclear matter, including the recent determinations of symmetry energy parameters. Our results show that the nucleon radius in free space have negligible effects on nuclear matter equation of state and neutron star mass-radius relations, which is different from the conclusion drawn in previous studies. We further explore that the sensitivity of star radius on the nucleon radius found in earlier publications is actually from the symmetry energy and its slope.