B–Bbar oscillation
Neutral B meson oscillations (or B–B oscillations) is one of the manifestations of the neutral particle oscillation, a fundamental prediction of the Standard Model of particle physics. It is the phenomenon of B mesons changing (or oscillating) between their matter and antimatter forms before their decay. The B
s meson can exist as either a bound state of a strange antiquark and a bottom quark, or a strange quark and bottom antiquark. The oscillations in the neutral B sector are analogous to the phenomena that produces long and short-lived neutral kaons.
B
s–B
s mixing was observed by the CDF experiment at Fermilab in 2006 and by LHCb at CERN in 2011.
Excess of matter over antimatter
The Standard Model predicts that regular matter B
s mesons are slightly favored in these oscillations over their antimatter counterpart, making strange B mesons of especial interest to particle physicists. The observation of the B–B mixing phenomena led physicists to propose the construction of 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.
On 14 May 2010, physicists at the Fermi National Accelerator Laboratory reported that the oscillations decayed into matter 1% more often than into antimatter, which may help explain the abundance of matter over antimatter in the observed Universe.[1] However, more recent results at LHCb in 2011 and 2012 with larger data samples have demonstrated no significant deviation from the Standard Model prediction of very nearly zero asymmetry.[2][3]
See also
- Kaon
- Strange B meson
- Baryogenesis
- CP Violation
References
- Paper describing the discovery of B-meson mixing by the ARGUS Collaboration
- Fermilab press release from April 2006
- September 2006 press release regarding 5 sigma discovery