The NLO jet vertex in the small-cone approximation for kt and cone algorithms

TL;DR

This paper calculates the jet vertex for Mueller-Navelet and forward jets using the small-cone approximation for kt and cone algorithms, highlighting differences from previous calculations and assessing approximation errors.

Contribution

It provides a detailed analytic and numerical comparison of the small-cone jet vertex for specific algorithms, improving accuracy in jet phenomenology calculations.

Findings

Differences with previous jet vertex calculations are significant.

Small-cone approximation introduces about 5% error in cross sections for R=0.5.

Error reduces to less than 2% for distribution ratios like azimuthal decorrelation.

Abstract

We determine the jet vertex for Mueller-Navelet jets and forward jets in the small-cone approximation for two particular choices of jet algoritms: the kt algorithm and the cone algorithm. These choices are motivated by the extensive use of such algorithms in the phenomenology of jets. The differences with the original calculations of the small-cone jet vertex by Ivanov and Papa, which is found to be equivalent to a formerly algorithm proposed by Furman, are shown at both analytic and numerical level, and turn out to be sizeable. A detailed numerical study of the error introduced by the small-cone approximation is also presented, for various observables of phenomenological interest. For values of the jet "radius" R=0.5, the use of the small-cone approximation amounts to an error of about 5% at the level of cross section, while it reduces to less than 2% for ratios of distributions such as those involved in the measure of the azimuthal decorrelation of dijets.