Observation of double charm production involving open charm in pp collisions at $\sqrt{s}$=7 TeV

Understand

The production of $J/\psi$ mesons accompanied by open charm, and of pairs of open charm hadrons are observed in pp collisions at a centre-of-mass energy of 7 TeV using an integrated luminosity of $355pb^{-1}$ collected with the LHCb detector.

• Model independent measurements of absolute cross-sections are given together with ratios to the measured $J/\psi$ and open charm cross-sections.
• The properties of these events are studied and compared to theoretical predictions.