Were the meson travelling faster than c, then there would be a standing wave (bow shock) in the ether (detectable, anyway.) This is analogous to the sonic boom emitted from a plane (or car) moving faster than the speed of sound.
Cerenkov radiation is an example.
Cerenkov radiation, the glow coming off a pile, our own 'black rock', is something that might make one wonder whether the idea of the speed of light being a limiting speed is right. After all, there are particles travelling faster than light in a medium other than pure vacuum where the index of refraction is 1.0000 . . .. There they are, not much doubt. Light travels slower in a medium, can even be brought to a crawl if the index of refraction is high enough. There is also the phenomenon where the index of refraction is less than one, mainly seen in some experiments with electronic devices such as special antennas. There is wiggle room. I don't know there would be a bow wave in the vacuum, that would imply a gradual loss of energy, but energy is given off all at once at some point when the particle decays.