We report evidence for the simultaneous production of $J/\psi$ and $\mathrm{\Upsilon }$ mesons in $8.1{\mathrm{fb}}^{-1}$ of data collected at $\sqrt{s}=1.96\mathrm{TeV}$ by the D0 experiment at the Fermilab $p\overline{p}$ Tevatron Collider. Events with these characteristics are expected to be produced predominantly by gluon-gluon interactions. In this analysis, we extract the effective cross section characterizing the initial parton spatial distribution, ${\sigma }_{\mathrm{eff}}=2.2\pm 0.7(\mathrm{stat})\pm 0.9(\mathrm{syst})\mathrm{mb}$.

• Received 9 November 2015

DOI:https://doi.org/10.1103/PhysRevLett.116.082002

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Published by the American Physical Society