H → ZZ as a double-slit experiment

The decay $H\to ZZ\to 4\ell$, with $\ell =e,\mu$, can be used to test quantum interference in analogy to the famous double-slit experiment. The observations corresponding to ‘covering a slit’ can be extracted from data in the $ee\mu \mu$ channel, while the observations when both ‘slits’ are open, which include the interference, are measured in the $4e/4\mu$ channels. In this way, this process offers a unique opportunity to investigate identical-particle effects at high energies, and provides the first evidence of identical-particle behaviour for muons. Sensitivity at the 4σ level could be achieved at the high-luminosity upgrade of the Large Hadron Collider.