During the Electroweak era, the Higgs mechanism had not yet distinguished particles such as electrons and muons by mass. Is there a conceivable experiment, or a hypothetical cosmological observation we could make today, that could have identified electrons and muons as distinct particles during that era? Alternatively, might there be features in the Cosmic Microwave Background or the distribution of matter in the early Universe that could reflect the distinction between the electron and muon fields prior to the onset of the Higgs mechanism?
