Song of the electroweak penguin

Abstract

An unexpected imbalance in how particles containing the heaviest quarks decay might reveal exotic influences — and perhaps help to explain why matter, rather than antimatter, dominates the Universe. The near disappearance of antimatter - predicted to have formed in equal quantities to matter in the Big Bang - is one of the reasons why life can even exist. A prerequisite for understanding the elimination of antimatter is the nonconservation of charge-parity (CP) symmetry. A paper from the Belle Collaboration, a large-scale experiment running at the 'B factory' electron-positron collider at the KEK high-energy physics laboratory in Japan, has tackled this thorny matter of fundamental physics by using 535 million B meson/anti-B meson pairs to measure CP-violating asymmetries. Previous work had suggested a difference in the decay of charged and neutral particles - an asymmetry in the decay rate of about +7% for charged B mesons and -10% for neutral B mesons. The new study reduces uncertainty on the charged particle decay rate asymmetry by a factor of 1.7, providing stronger evidence for a large deviation in direct CP violation between charged and neutral B meson decays.