Contribution of two particle-two hole final states to the nuclear response

TL;DR

This paper investigates the role of two particle-two hole final states in neutrino-nucleus scattering, providing detailed calculations of nuclear responses and introducing a new method for handling complex amplitudes.

Contribution

It presents a novel approach for consistently treating one- and two-nucleon currents in nuclear response calculations beyond the non-relativistic limit.

Findings

Two particle-two hole states significantly contribute to the nuclear response.

The new method improves the accuracy of amplitude calculations in relativistic regimes.

Results help explain the excess cross section observed in experiments.

Abstract

The excitation of two particle-two hole final states in neutrino-nucleus scattering has been advocated by many authors as the source of the excess cross section observed by the MiniBooNE Collaboration in the quasi elastic sector. We analyse the mechanisms leading to the appearance of these final states, and illustrate their significance through the results of accurate calculations of the nuclear electromagnetic response in the transverse channel. A novel approach, allowing for a consistent treatment of the amplitudes involving one- and two-nucleon currents in the kinematical region in which the non relativistic approximation breaks down, is outlined.