  Forthcoming fixed-target coherent elastic neutrino-nucleus scattering
experiments aim at measurements with $\cal{O}(\text{tonne})$-scale detectors
and substantially reduced systematic and statistical uncertainties. With such
high quality data, the extraction of point-neutron distributions mean-square
radii requires a better understanding of possible theoretical uncertainties. We
quantify the impact of single-nucleon electromagnetic mean-square radii on the
weak-charge form factor and compare results from weak-charge form factor
parametrizations and weak-charge form factor decompositions in terms of elastic
vector proton and neutron form factors, including nucleon form factors
$Q$-dependent terms up to order $Q^2$. We assess as well the differences
arising from results derived using weak-charge form factor decompositions in
terms of elastic vector proton and neutron form factors and a model-independent
approach based solely on the assumption of spherically symmetric nuclear ground
state. We demonstrate the impact of the main effects by assuming pseudo-data
from a one-tonne LAr detector and find that, among the effects and under the
assumptions considered in this paper, weak-charge form factor parametrizations
and weak-charge form factor decompositions in terms of elastic vector proton
and neutron form factors enable the extraction of the $^{40}\text{Ar}$
point-neutron distribution mean-square radius with a $\sim 15\%$ accuracy. With
a substantial reduction of the beam-related neutron and steady-state
backgrounds a $\sim 1\%$ precision extraction seems feasible, using either of
the two approaches.

High Energy Physics - Phenomenology;High Energy Physics - Experiment;Nuclear Experiment;Nuclear Theory