Empty On The Inside

Given that $a_\psi$ exist in 3D space,

The particle is confined in a spherical shell of thickness $2x_z$ and radius $a_\psi$.  There is nothing in the center in the case of a photon.  The outer radius of this shell is given by,

$r_{outer}=a_\psi+x_z$

This is the measured size of the particle.