The formula: pi- -> e- + electron antineutrino is in error. The correct formula is: pi- + tachyon -> e- + electron antineutrino and this conserves parity. This way there is a cause to the decay. The way to test this is: do a pi-minus creating event and put a periodic phenomenon close by, with the control: a pi-minus creating event without the periodic phenomenon. And measure the decay lifetime.