Measurement of the exclusive Υ production cross-section in pp collisions at s = 7 √s=7 TeV and 8 TeV

A study is presented of central exclusive production of Υ(nS) states, where the Υ(nS) resonances decay to the μ + μ − final state, using pp collision data recorded by the LHCb experiment. The cross-section is measured in the rapidity range 2 < y(Υ) < 4.5 where the muons are reconstructed in the pseudorapidity range 2 < η(μ ±) < 4.5. The data sample corresponds to an integrated luminosity of 2.9 fb−1 and was collected at centre-of-mass energies of 7 TeV and 8 TeV. The measured Υ(1S) and Υ(2S) production cross-sections are $$ σ ( pp→ pY(1S)p)=9.0± 2.1± 1.70.5em pb0.5em and0.5em σ ( pp→ pY(2S)p)=1.3± 0.8± 0.30.5em pb, $$ where the first uncertainties are statistical and the second are systematic. The Υ(1S) crosssection is also measured as a function of rapidity and is found to be in good agreement with Standard Model predictions. An upper limit is set at 3.4 pb at the 95% confidence level for the exclusive Υ(3S) production cross-section, including possible contamination from χ b (3P ) → Υ(3S)γ decays.