  In their 1997 paper, CDF measured sigma_effective, the normalization factor
that relates the cross section for double parton scattering to the product of
the inclusive cross sections of the two individual scatters, in a model in
which they are assumed to be independent. In his 2007 paper, Treleani pointed
out that CDF used a non-standard definition, in which the double parton
scattering cross section corresponds to exactly two scatters, rather than the
more conventional one in which it is the inclusive two-scatter cross section.
He also estimated the correction from one definition to the other, to give a
corrected value of sigma_effective. Treleani's form would be correct under the
assumption that CDF were able to uniquely identify and count the number of
scatters in an event, which is certainly not the case. In this publication we
consider CDF's event definition in more detail to provide an improved
correction.
