The EMC effect for few-nucleon bound systems in Light-Front Hamiltonian Dynamics

TL;DR

This paper extends the light-front formalism to describe the EMC effect in any nucleus, accurately predicting effects in $^3$He, $^3$H, and $^4$He, and analyzing the impact of short-range correlations and neutron-proton structure function ratios.

Contribution

It provides a covariant light-front approach for nuclear structure functions applicable to all nuclei, incorporating realistic nuclear potentials and sum rules, and analyzing effects of correlations and nucleon structure ratios.

Findings

Predicted sizable EMC effect for $^4$He consistent with observations.

Short-range correlations influence the depth of the EMC ratio minimum.

Uncertainties from neutron-proton structure function ratios are very small.

Abstract

The light-front formalism for a covariant description of the European Muon Collaboration (EMC) effect, already applied to $^3$He, is formally extended to any nucleus, and used for actually calculating the $^3$H and $^4$He cases. The realistic and accurate nuclear description of few-nucleon bound systems, obtained with both phenomenological and chiral potentials, has been properly combined with the Poincare' covariance and macroscopic locality, automatically satisfying both number of particles and momentum sum rule. While retaining the on-mass-shell nucleon structure functions, one is then able to predict a sizable EMC effect for $^4$He, as already observed for $^3$He. Moreover, the impact on the EMC effect of both i) the short-range correlations, such as those generated by modern nuclear interactions, and ii) the ratio between the neutron and proton structure functions has been studied. The short-range correlations generated by retaining only the standard nuclear degrees of freedom act on the depth of the minimum in the EMC ratio, while the uncertainties linked to the ratio of neutron to proton structure functions are found to be very small. These light-front results facilitates ascribing deviations from experimental data due to genuine QCD effects, not included in a standard nuclear description, and initiating unbiased investigations.