  Understanding the structure of the nucleon (proton and neutron) is a critical
problem in physics. Especially challenging is to understand the spin structure
when the Strong Interaction becomes truly strong. At energy scales below the
nucleon mass (~1 GeV), the intense interactions of the quarks and gluons inside
the nucleon makes them highly correlated. Their coherent behavior causes the
emergence of effective hadronic degrees of freedom (hadrons are composite
particles made of quarks and gluons) which are necessary to understand the
nucleon properties. Theoretically studying this subject requires approaches
employing non-perturbative techniques or using hadronic degrees of freedom,
e.g. chiral effective field theory (chiEFT). Here, we present measurements
sensitive to the neutron's spin precession under electromagnetic fields. The
observables, the generalized spin-polarizabilities delta_LT and gamma_0, which
quantify the nucleon spin's precession, were measured at very low
energy-momentum transfer squared Q^2 corresponding to probing distances of the
size of the nucleon. Our Q^2 values match the domain where chiEFT calculations
are expected to be applicable. The calculations have been conducted to high
degrees of sophistication, including that of the so-called "gold-plated"
observable, delta_LT. Surprisingly however, our data show a strong discrepancy
with the chiEFT calculations. This presents a challenge to the current
description of the neutron's spin properties.
