F. Abe et al., DOUBLE PARTON SCATTERING IN (P)OVER-BAR-P COLLISIONS AT ROOT-S=1.8 TEV, Physical review. D. Particles and fields, 56(7), 1997, pp. 3811-3832
A strong signal for double parton (DP) scattering is observed in a 16
pb(-1) sample of <(p)over bar p> --> gamma/pi(0) + 3 jets + X data fro
m the CDF experiment at the Fermilab Tevatron. In DP events, two separ
ate hard scatterings take place in a single <(p)over bar p> collision.
We isolate a large sample of data (similar to 14 000 events) of which
53% are found to be DP. The process-independent parameter of double p
arton scattering, sigma(eff), is obtained without reference to theoret
ical calculations by comparing observed DP events to events with hard
scatterings in separate <(p)over bar p> collisions. The result sigma(e
ff) = (14.5 +/- 1.7(-2.3)(+1.7)) mb represents a significant improveme
nt over previous measurements, and is used to constrain simple models
of parton spatial density. The Feynman x dependence of sigma(eff) is i
nvestigated and none is apparent. Further, no evidence is found for ki
nematic correlations between the two scatterings in DP events.