UC Davis

The yield of simultaneous uncorrelated production of Upsilon+J/psi mesons in Pb+Pb collisions at sqrt(sNN) = 5.02 TeV is measured for the first time using data collected by the CMS experiment. Reconstructed Upsilon and J/psi candidates are paired together to make a two-dimensional invariant mass distribution, which is fitted with a four-component model that accounts for total signal of correlated+uncorrelated Upsilon+J/psi, single-quarkonia Upsilon+mumu and J/psi+mumu, and pure background mumu+mumu. The total signal of correlated+uncorrelated Ups+J/psi directly from the fit is consistent with zero. A new method is devised to calculate the uncorrelated Upsilon+J/psi yield alone from the three other fit components, thereby reducing the statistical uncertainty. Using this method, the yield of uncorrelated Upsilon+J/psi in the kinematic range (pt_mumu<30 GeV, y_mumu<2.4) is measured to be 1325 +/- 378 (stat.) +/- 437 (sys.), which is a statistically significant signal of over 3 sigma. We compare our result to theoretical predictions from a model of correlated and uncorrelated production based on double-parton scattering, and to Glauber Monte Carlo simulations. We find that the model and simulations are consistent with our result within systematic uncertainties. The methods used in this first measurement of Upsilon+J/psi in heavy-ion collisions may be useful for future analyses with greater quantities of data.