Observation of $J/\ddot{I}ˆ$ pair production in pp collisions at $\sqrt{s}=7TeV$

Abstract

The production of $J/\ddot{I}ˆ$ pairs in proton-proton collisions at a centre-of-mass energy of 7 TeV has been observed using an integrated luminosity of $37.5p{b}^{-1}$ collected with the LHCb detector. The production cross-section for pairs with both \jpsi in the rapidity range $2<y^{J/\ddot{I}ˆ}<4.5$ and transverse momentum $p_T^{J/\ddot{I}ˆ}<10GeV/c$ is $$\ddot{I}{ƒ}^{J/\ddot{I}ˆJ/\ddot{I}ˆ}=5.1\pm 1.0\pm 1.1nb,$$ where the first uncertainty is statistical and the second systematic.

10 pages, 3 figures