  We study the full counting statistics of interferometers for chiral Majorana
fermions with two incoming and two outgoing Dirac fermion channels. In the
absence of interactions, the FCS can be obtained from the $4\times4$ scattering
matrix $S$ that relates the outgoing Dirac fermions to the incoming Dirac
fermions. After presenting explicit expressions for the higher-order current
correlations for a modified Hanbury Brown-Twiss interferometer, we note that
the cumulant-generating function can be interpreted such that unit-charge
transfer processes correspond to two independent half-charge transfer
processes, or alternatively, to two independent electron-hole conversion
processes. By a combination of analytical and numerical approaches, we verify
that this factorization property holds for a general $SO(4)$ scattering matrix,
i.e. for a general interferometer geometry.
