Double parton scattering in $p\bar p$ interactions at $\sqrt{s} = 1.96$ TeV

Abstract

We present the observation of doubly produced $$J / \psi$$ mesons as an example of processes containing a substantial fraction of double parton scattering. Measurements of the production cross sections for singly and doubly-produced $$J/\psi$$ mesons were done with the D0 detector at Fermilab in $$p\bar{p}$$ collisions at $$\sqrt{s}$$ = 1.96 TeV with an integrated luminosity of 8.1 fb$$^{-1}$$. For the first time, the double $$J / \psi$$ production cross section is separated into two parts: contributions from both single and double parton scattering. Lastly, this separation allowed us to determine the effective cross section σ eff, a parameter related to the parton spatial density inside the hadron.