  It is shown that the Quark-Level Linear $\sigma$ Model (QLL$\sigma$M) leads
to a prediction for the diamagnetic term of the polarizabilities of the nucleon
which is in excellent agreement with the experimental data. The bare mass of
the $\sigma$ meson is predicted to be $m_\sigma=666$ MeV and the two-photon
width $\Gamma(\sigma\to\gamma\gamma)=(2.6\pm 0.3)$ keV. It is argued that the
mass predicted by the QLL$\sigma$M corresponds to the $\gamma\gamma\to\sigma\to
NN$ reaction, i.e. to a $t$-channel pole of the $\gamma N\to N\gamma$ reaction.
Large -angle Compton scattering experiments revealing effects of the $\sigma$
meson in the differential cross section are discussed. Arguments are presented
that these findings may be understood as an observation of the Higgs boson of
strong interaction while being part of the constituent quark.
