Spectral functions of argon and calcium

TL;DR

This paper presents approximate spectral functions for argon and calcium nuclei, validated against electron-scattering data, and shows their impact on neutrino cross section predictions, highlighting deviations from simpler models.

Contribution

It introduces improved spectral functions for argon and calcium and demonstrates their application in more accurate neutrino cross section calculations.

Findings

Spectral functions for argon and calcium are developed and validated.

Calculated neutrino cross sections differ significantly from Fermi gas model predictions.

Validation against electron-scattering data supports the approach's accuracy.

Abstract

Precise knowledge of the cross sections for neutrino interactions with nuclei is important not only for existing experiments but also for development of future detectors. When momentum transferred to the nucleus by the probe is high enough, the impulse approximation is valid, i.e. the nucleus can be described as composed of independent nucleons and the interaction happens between neutrino and a single bound nucleon. The cross section of the nucleus is then expressed as an integral of the free cross section (modified by the off-shell effect) folded with the so-called spectral function, describing the distribution of nucleon momenta and energies. I present results obtained for the approximate spectral functions of argon and calcium. The accuracy of the approach is verified by comparison with a broad spectrum of precise electron-scattering data for the calcium target. Some of these data lie in the kinematical region corresponding to neutrino interactions what indirectly shows that a similar level of accuracy is achieved for neutrinos. The calculated Ar(nu_mu,mu) cross section is significantly lower than the one predicted within the Fermi gas model.