Neutral particle oscillation

In particle physics, neutral particle oscillation is the transmutation of a particle with zero electric charge into another neutral particle due to a change of a non-zero internal quantum number via an interaction that does not conserve that quantum number. For example, a neutron cannot transmute into an antineutron as that would violate the conservation of baryon number.

Such oscillations can be classified into two types:

In case the particles decay to some final product, then the system is not purely oscillatory, and an interference between oscillation and decay is observed.

After the striking evidence for parity violation provided by Wu et al. in 1957, it was assumed that CP (charge conjugation-parity) is the quantity which is conserved. However, in 1964 Cronin and Fitch reported CP violation in the neutral Kaon system. They observed the long-lived K₂ (CP = −1) undergoing two pion decays (CP = (−1)(−1) = +1), thereby violating CP conservation.

In 2001, CP violation in the
B0
–
B0
system was confirmed by the BaBar and the Belle experiments. Direct CP violation in the
B0
–
B0
system was reported by both the labs by 2005.

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