Phenomenology of event shapes at hadron colliders

TL;DR

This paper advances the precision of theoretical predictions for dijet event shapes at hadron colliders by combining multiple levels of logarithmic accuracy and NLO calculations, enabling better constraints on QCD and new physics searches.

Contribution

First matching of NLL, NNLL, and NLO accuracies for hadronic event shapes at colliders, improving theoretical precision and comparison with Monte Carlo models.

Findings

Event shapes can constrain perturbative and non-perturbative QCD.

Differences in calculation methods reveal limits of scale variation for uncertainty estimates.

Event shapes are sensitive to multi-jet topologies relevant for New Physics.

Abstract

We present results for matched distributions of a range of dijet event shapes at hadron colliders, combining next-to-leading logarithmic (NLL) accuracy in the resummation exponent, next-to-next-to leading logarithmic (NNLL) accuracy in its expansion and next-to-leading order (NLO) accuracy in a pure alpha_s expansion. This is the first time that such a matching has been carried out for hadronic final-state observables at hadron colliders. We compare our results to Monte Carlo predictions, with and without matching to multi-parton tree-level fixed-order calculations. These studies suggest that hadron-collider event shapes have significant scope for constraining both perturbative and non-perturbative aspects of hadron-collider QCD. The differences between various calculational methods also highlight the limits of relying on simultaneous variations of renormalisation and factorisation scale in making reliable estimates of uncertainties in QCD predictions. We also discuss the sensitivity of event shapes to the topology of multi-jet events, which are expected to appear in many New Physics scenarios.