B–Bbar oscillation

The observation of the B–B mixing phenomena led physicists to propose the construction of the so-named "B factories" in the early 1990s.

They realized that a precise B–B oscillation measure could pin down the unitarity triangle and perhaps explain the excess of matter over antimatter in the universe.

To this end construction began on two "B factories" in the late nineties, one at the Stanford Linear Accelerator Center (SLAC) in California and one at KEK in Japan.

These B factories, BaBar and Belle, were set at the ϒ(4S) resonance which is just above the threshold for decay into two B mesons.

[1] However, more recent results at LHCb in 2011, 2012, and 2021 with larger data samples have demonstrated no significant deviation from the Standard Model prediction of very nearly zero asymmetry.

B-bar oscillations detected via their respective D meson and Pion decays as seen by the LHCb in 2021. stands for the oscillation process .
The oscillations are mediated by the W boson and the top quark ; being heavier than the
B
s –
B
s mesons, they act as short lived virtual particles