Measurement of the production cross-section in collisions at

Using a data sample corresponding to an integrated luminosity of 2.0 , collected by the LHCb experiment, the production of the state in proton–proton collisions at a centre-of-mass energy of is studied in the rapidity range and in the transverse momentum range . The cross-section for prompt production of mesons relative to that of the meson is measured using the decay mode and is found to be . The quoted uncertainties are, in order, statistical, systematic and due to uncertainties on the branching fractions of the and decays. The prompt production cross-section is determined to be , where the last uncertainty includes that on the meson cross-section. The ratio of the branching fractions of -hadron decays to the and states is measured to be , where the last uncertainty is due to those on the branching fractions of the and decays. The difference between the and masses is also determined to be , which is the most precise single measurement of this quantity to date.