The ground state of bottomonium.
η b is the name of the particle recently discovered by the physicists working on the BaBar experiment.This ground state of ‘bottomonium’, a collection of particles formed from a bottom quark and an anti-bottom quark, has been sought for over thirty years. It has now been identified in the disintegration products of the Y(3S) particle, an excited state of bottomonium, using the latest data taken in 2008 by the BaBar experiment.