  The simplest three-level system exhibiting electromagnetically induced
transparency (EIT) exhibits an effective conjugation symmetry as well as a
permutation symmetry. Breaking conjugation symmetry leads to a distinct chirp
asymmetry; the differential response to a frequency increase versus a frequency
decrease. Hanle-Zeeman EIT resonance is an ideal platform for testing the
theory of chirp asymmetry because so many optical parameters of the system can
be changed experimentally. We describe the theory and compare it to an
experiment using 87Rb in a buffer gas cell. In contrast with earlier
multi-photon chirp asymmetry work this present effort explores the asymmetry at
nearly one billionth the earlier chirp rate, yet displays its universal
features. Chirp asymmetry may have metrological consequences for understanding
systematic dependence on modulation/demodulation parameters.
