  We consider a ballistic Mach-Zehnder interferometer for electrons propagating
chirally in one dimension (such as in an integer Quantum Hall effect edge
channel). In such a system, dephasing occurs when the finite range of the
interaction potential is taken into account. Using the tools of bosonization,
we discuss the decay of coherence as a function of propagation distance and
energy. We supplement the exact solution by a semiclassical approach that is
physically transparent and is exact at high energies. In particular, we study
in more detail the recently predicted universal power-law decay of the
coherence at high energies, where the exponent does not depend on the
interaction strength. In addition, we compare against Keldysh perturbation
theory, which works well for small interaction strength at short propagation
distances.
