Electromagnetic and neutral-weak response functions of 4He and 12C

TL;DR

This paper presents ab initio calculations of electromagnetic and neutral-weak response functions for helium-4 and carbon-12, revealing the significant role of two-body currents in nuclear responses, challenging traditional single-nucleon models.

Contribution

First ab initio calculations of these response functions using Green's function Monte Carlo and maximum-entropy methods, incorporating realistic nuclear interactions and two-body currents.

Findings

Two-body currents generate excess transverse strength.

Results confirm experimental data for electromagnetic responses.

Challenges the single-nucleon knockout dominance in quasi-elastic scattering.

Abstract

Ab initio calculations of the quasi-elastic electromagnetic and neutral-weak response functions of 4He and 12C are carried out for the first time. They are based on a realistic approach to nuclear dynamics, in which the strong interactions are described by two- and three-nucleon potentials and the electroweak interactions with external fields include one- and two-body terms. The Green's function Monte Carlo method is used to calculate directly the Laplace transforms of the response functions, and maximum-entropy techniques are employed to invert the resulting imaginary-time correlation functions with associated statistical errors. The theoretical results, confirmed by experiment in the electromagnetic case, show that two-body currents generate excess transverse strength from threshold to the quasi-elastic to the dip region and beyond. These findings challenge the conventional picture of quasi-elastic inclusive scattering as being largely dominated by single-nucleon knockout processes.