Central Rapidity Gaps in Events with a Leading Antiproton at CDF
Mary Convery
The Rockefeller University
QCD calculations of hard diffractive processes, such as jet-gap-jet
production rates, are hampered by the so-called gap survival
probability, which is due to non-perturbative effects that suppress
rapidity gap formation. Eliminating the gap survival probability
experimentally would allow measurements to be compared directly to QCD
calculations. This can be done by using events with multiple gaps, since
if in a given event a single gap survives, additional gaps would also be
expected to survive.
This idea was tested in the soft diffraction sector. From a sample of
single-diffractive (SD) events collected by CDF in Run I by triggering
on a leading antiproton (which already have a forward rapidity gap), we
measure the fraction of events with an additional gap (SDD) to be
0.246 ± 0.001(stat) ± 0.042(syst)
[0.184 ± 0.001(stat) ± 0.043(syst)] at sqrt(s)=1800 [630] GeV.
These results are compared with gap fractions which we previously
measured in minimum-bias pbar-p collisions. The ratio of (2-gap/1-gap)
to (1-gap/0-gap) fractions gives a suppression in gap rates due to
non-perturbative effects of a factor of approximately 2.5.
The renormalized gap-model of Goulianos predicts the fraction of SDD/SD
rates to be approximately kappa = g(t)/beta(0) = 0.17 ± 0.02, where g(0)
and beta(0) are the Pomeron-proton and proton-proton couplings,
respectively. This prediction is consistent with our results.