On QCD resummation with kt clustering

TL;DR

The paper analyzes how the kt clustering jet algorithm affects QCD resummation of energy flow into gaps between jets. It provides an analytic treatment of the primary emission component under clustering, revealing explicit R^3, R^5, and R^6 clustering corrections and an all-orders structure (up to R^6) for the Sudakov-like term, while noting a substantial suppression of the non-global component. The authors show that clustering modifies the real-virtual cancellations, derive multi-gluon contributions (2, 3, 4 gluons) to the primary term, and present an exponentiated form that can be used in phenomenology, including improved agreement with ZEUS photoproduction data. These results sharpen predictive control over jet-gap observables and inform resummations for a broader class of jet-based observables in experimental analyses.

Abstract

We revisit the impact of the jet algorithm on predictions of energy flow into gaps between hard jets, defined using the kt clustering procedure. The resulting prediction has two distinct components: a primary emission piece that is related to independent emission of soft gluons by the hard jets and a correlated emission (non-global) piece known only in the large N_c limit. We analytically compute the dependence of the primary emission term on the jet algorithm, which gives significantly more insight than our previous numerical study of the same. We also point out that the non-global component of the answer is reduced even more significantly by the clustering than suggested previously in the literature. Lastly we provide improved predictions for the latest ZEUS photoproduction data, assessing the impact of our latest findings.