CMS and LHCb experiments reveal new rare particle decay
In an article published in Nature, the CMS and LHCb collaborations describe the first observation of the very rare decay of the B0s particle into two muon particles. The Standard Model, the theory that best describes the world of particles, predicts that this rare subatomic process happens about four times out of a billion decays, but it has never been seen before. These decays are studied as they could open a window to theories beyond the Standard Model, such as supersymmetry. The analysis is based on data taken at the Large Hadron Collider (LHC) in 2011 and 2012. These data also contain early hints of a similar, but even more rare decay into two muons of the B0, a cousin of the B0s. This is the first time that CMS and LHCb have analysed their data together.
The Helsinki Institute of Physics is actively involved in the study of B0s mesons in the CMS experiment. The study is currently concentrating on the properties of the decay B0s → J/ψ φ. This decay is particularly interesting, because the decay is affected by a phenomenon, which is connected to the asymmetry between matter and antimatter in the Universe. Even though the effect is weak, it can be predicted precisely by the Standard Model, thus enabling us to test the Standard Model and the mystery of matter-antimatter symmetry.