Two-Pion Exchange Currents in Photodisintegration of the Deuteron

TL;DR

This paper investigates the role of two-pion exchange currents derived from chiral effective field theory in deuteron photodisintegration, comparing theoretical predictions with experimental data to assess their significance and uncertainties.

Contribution

It introduces parameter-free two-pion exchange current operators at next-to-leading order in chiral EFT and applies them to deuteron photodisintegration analysis.

Findings

Two-pion exchange currents significantly affect certain observables.

Predictions closely match experimental data for some observables.

Theoretical uncertainties are estimated using multiple chiral potentials.

Abstract

Chiral effective field theory (ChEFT) is a modern framework to analyze the properties of few-nucleon systems at low energies. It is based on the most general effective Lagrangian for pions and nucleons consistent with the chiral symmetry of QCD. For energies below the pion-production threshold it is possible to eliminate the pionic degrees of freedom and derive nuclear potentials and nuclear current operators solely in terms of the nucleonic degrees of freedom. This is very important because, despite a lot of experience gained in the past, the consistency between two-nucleon forces, many-nucleon forces and the corresponding current operators has not been achieved yet. In this presentation we consider the recently derived long-range two-pion exchange (TPE) contributions to the nuclear current operator which appear at next-to leading order of the chiral expansion. These operators do not contain any free parameters. We study their role in the deuteron photodisintegration reaction and compare our predictions with experimental data. The bound and scattering states are calculated using five different chiral N2LO nucleon-nucleon (NN) potentials which allows to estimate the theoretical uncertainty at a given order in the chiral expansion. For some observables the results are very close to the reference predictions based on the AV18 NN potential and the current operator (partly) consistent with this force.