EMC effect, short-range nuclear correlations, neutron stars

TL;DR

This paper investigates the EMC effect and short-range correlations in nuclei, showing that photon contributions and SRCs explain a significant part of the EMC effect and have implications for neutron star properties.

Contribution

The study provides a model-independent evaluation of photon contributions and links SRCs to the EMC effect and neutron star observations.

Findings

Photon contributions reduce the EMC effect by ~50% for x ≤ 0.55.

SRCs account for the remaining EMC effect at x ≥ 0.5.

Large pn SRCs influence neutron star cooling rates.

Abstract

The recent x>1 (e,e') and correlation experiments at momentum transfer Q^2 \ge 2 GeV^2 confirm presence of short-range correlations (SRC) in nuclei mostly build of nucleons. Recently we evaluated in a model independent way the dominant photon contribution to the nuclear structure. Taking into account this effect and using definition of x consistent with the exact kinematics of eA scattering (with exact sum rules) results in the significant reduction of R_A(x,Q^2)=F_{2A}(x,Q^2)/F_{2N}(x,Q^2) ratio which explains \sim 50% of the EMC effect for x\le 0.55 where Fermi motion effects are small. The remaining part of the EMC effect at $x\ge 0.5$ is consistent with dominance of the contribution of SRCs. Implications for extraction of the F_{2n}/F_{2p} ratio are discussed. Smallness of the non-nucleonic degrees of freedom in nuclei matches well the recent observation of a two-solar mass neutron star, and while large pn SRCs lead to enhancement of the neutron star cooling rate for kT\le 0.01 MeV.