Hard Colour Singlet Exchange at the Tevatron
Brian Cox, Jeff Forshaw, Leif Lonnblad
TL;DR
This paper tackles the QCD description of diffractive gaps-between-jets via hard colour-singlet exchange by applying a leading-logarithmic BFKL framework to the hard subprocess while treating the strong coupling as a fixed parameter. It incorporates the gap-survival probability through a Pythia-based model of multiple parton interactions to account for underlying-event effects, and compares predictions to Tevatron data (DØ, 630 and 1800 GeV) as well as HERA results. The main finding is that the Tevatron data are broadly consistent with LO BFKL when $\alpha_s \approx 0.17$ is used and when the jet-energy correction and gap-survival factors are applied; the inferred gap-survival factors are $S_{1800}=0.22$, $S_{630}=0.35$, and $S_{\text{HERA}}=0.67$. The study highlights large hadronisation/showering corrections and significant normalization uncertainties tied to scale choices, and notes tensions with CDF data at large $\Delta\eta$, arguing for higher-order BFKL, non-zero-$t$ effects, and improved underlying-event modeling in future work.
Abstract
We have performed a detailed phenomenological investigation of the hard colour singlet exchange process which is observed at the Tevatron in events which have a large rapidity gap between outgoing jets. We include the effects of multiple interactions to obtain a prediction for the gap survival factor. Comparing the data on the fraction of gap events with the prediction from BFKL pomeron exchange we find agreement provided that a constant value of alpha_s is used in the BFKL calculation. Moreover, the value of alpha_s is in line with that extracted from measurements made at HERA.