Relativistic effects in ab-initio electron-nucleus scattering

TL;DR

This paper extends Green's function Monte Carlo calculations to include relativistic effects in electron-nucleus scattering, improving accuracy for intermediate momentum transfers and aiding neutrino-oscillation data analysis.

Contribution

It introduces a novel relativistic extension of GFMC calculations and a new algorithm for computing inclusive cross sections, enhancing the modeling of nuclear responses.

Findings

Excellent agreement with experimental cross sections across various kinematics

Effective incorporation of relativistic effects improves theoretical predictions

Method facilitates better analysis for neutrino-oscillation experiments

Abstract

The electromagnetic responses obtained from Green's function Monte Carlo (GFMC) calculations are based on realistic treatments of nuclear interactions and currents. The main limitations of this method comes from its nonrelativistic nature and its computational cost, the latter hampering the direct evaluation of the inclusive cross sections as measured by experiments. We extend the applicability of GFMC in the quasielastic region to intermediate momentum transfers by performing the calculations in a reference frame that minimizes nucleon momenta. Additional relativistic effects in the kinematics are accounted for employing the two-fragment model. In addition, we developed a novel algorithm, based on the concept of first-kind scaling, to compute the inclusive electromagnetic cross section of $^4$He through an accurate and reliable interpolation of the response functions. A very good agreement is obtained between theoretical and experimental cross sections for a variety of kinematical setups. This offers a promising prospect for the data analysis of neutrino-oscillation experiments that requires an accurate description of nuclear dynamics in which relativistic effects are fully accounted for.