Abstract:
A strong signal for double parton (DP) scattering is observed in a 16 pb-1 sample of p̄p→γ/π0 + 3 jets + X data from the CDF experiment at the Fermilab Tevatron. In DP events, two separate hard scatterings take place in a single p̄p collision. We isolate a large sample of data (≃ 14 000 events) of which 53% are found to be DP. The process-independent parameter of double parton scattering, σeff, is obtained without reference to theoretical calculations by comparing observed DP events to events with hard scatterings in separate p̄p collisions. The result σeff=(14.5±1.7+1.7-2.3) mb represents a significant improvement over previous measurements and is used to constrain simple models of parton spatial density. The Feynman x dependence of σeff is investigated and none is apparent. Further, no evidence is found for kinematic correlates between the two scatterings in DP events.