文摘
The first observation of the decay using pp data collected by the LHCb detector at a centre-of-mass energy of 7 TeV, corresponding to an integrated luminosity of , is reported. A signal of events is obtained and the absence of signal is rejected with a statistical significance of more than nine standard deviations. The branching fraction is measured relative to that of : , where the first uncertainty is statistical, the second systematic and the third is due to the uncertainty on the ratio of the and hadronisation fractions.