B–Bbar oscillation

From Wikipedia, the free encyclopedia
  (Redirected from B-Bbar oscillation)
Jump to: navigation, search

Neutral B meson oscillations (or BB 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
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.

mixing was observed by the CDF experiment at Fermilab in 2006 and by LHCb at CERN in 2011.

Excess of matter over antimatter[edit]

Main article: B-factory

The Standard Model predicts that regular matter B
are slightly favored in these oscillations over their antimatter counterpart, making strange B mesons of especial interest to particle physicists. The observation of the BB mixing phenomena led physicists to propose the construction of B-factories in the early 1990s. They realized that a precise BB 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[edit]


External links[edit]