Average CsI neutron density distribution from COHERENT data

TL;DR

This paper uses COHERENT experiment data to measure the average neutron radius of cesium-133 and iodine-127 nuclei, providing a model-independent estimate and evidence of nuclear structure effects on coherence.

Contribution

First determination of the neutron rms radius for $^{133}$Cs and $^{127}$I using coherent neutrino scattering data with minimal model dependence.

Findings

Neutron rms radius $ R_{n} = 5.5^{+0.9}_{-1.1}$ fm for cesium-133 and iodine-127.

Evidence of nuclear structure suppression of coherence at 2.3 sigma.

Model-independent extraction using symmetrized Fermi and Helm form factors.

Abstract

Using the coherent elastic neutrino-nucleus scattering data of the COHERENT experiment, we determine for the first time the average neutron rms radius of $^{133}\text{Cs}$ and $^{127}\text{I}$. We obtain the practically model-independent value $ R_{n} = 5.5 {}^{+0.9}_{-1.1} \, \text{fm} $ using the symmetrized Fermi and Helm form factors. We also point out that the COHERENT data show a $2.3\sigma$ evidence of the nuclear structure suppression of the full coherence.