  Photons experience mirror asymmetry of macroscopic chiral media, as in
circular dichroism and polarization rotation, since left and right handed
circular polarizations differently couple with matter handedness. Conversely,
free relativistic electrons with vanishing orbital angular momentum have no
handedness so the question arises whether they could sense chirality of
geometrically symmetric macroscopic samples. In this Letter, we show that
matter chirality breaks mirror symmetry of the scattered electrons quantum
decoherence, even when the incident electron wave function and the sample shape
have a common reflection symmetry plane. This is physically possible since the
wave function transverse smearing triggers electron sensitivity to the spatial
asymmetry of the electromagnetic interaction with the sample, as results from
our non-perturbative analysis of the scattered electron reduced density matrix,
in the framework of macroscopic quantum electrodynamics. Furthermore, we prove
that mirror asymmetry also shows up in the distribution of the electron lateral
momentum, orthogonal to the geometric symmetry plane, whose non-vanishing mean
value reveals that the electron experiences a lateral mechanical interaction
entirely produced by matter chirality.
