1998/07/20 by ZEUS Collaboration · 1 citation
Physics and Astronomy · #hep-ex
paper · pdf · doi:10.1016/s0370-2693(98)01081-8
published as Phys.Lett.B437:432-444,1998 · 13 pages including 3 figures
arxiv created 1998/07/20 · arxiv updated 2012/08/27
The photoproduction reaction gamma p -> mu+ mu- p has been studied in ep interactions using the ZEUS detector at HERA. The data sample corresponds to an integrated luminosity of 43.2 pb-1. The Upsilon meson has been observed in photoproduction for the first time. The sum of the products of the elastic Upsilon(1S), Upsilon(2S), Upsilon(3S) photoproduction cross sections with their respective branching ratios is determined to be 13.3 +- 6.0(stat.)+2.7-2.3(syst.) pb at a mean photon-proton centre of mass energy of 120 GeV. The cross section is above the prediction of a perturbative QCD model.