Measurement of Double Parton Scattering inp¯pCollisions ats}=1.8TeV

A strong signal for double parton scattering (DP) is observed in a 16 pb{sup {minus}1} sample of {bar p}p{r_arrow}{gamma}+3 jets+X data from the CDF experiment at the Fermilab Tevatron. The process-independent DP parameter, {sigma}{sub eff}, is obtained without reference to theoretical calculations by comparing observed DP events to events with hard scatterings at separate {bar p}p collisions. The result, {sigma}{sub eff}=(14.5{plus_minus}1.7{sup +1 .7}{sub {minus}2.3}) mb , represents a significant improvement over previous measurements. For the first time, the Feynman x dependence of the {sigma}{sub eff} parameter is investigated, and no dependence is seen. {copyright} {ital 1997} {ital The American Physical Society}