Event shape–energy flow correlations

Abstract

We introduce a set of correlations between energy flow and event shapes that are sensitive to the flow of color at short distances in jet events. These correlations are formulated for a general set of event shapes, which includes jet broadening and thrust as special cases. We illustrate the method for e + e − dijet events, and calculate the correlation at leading logarithm in the energy flow and at next-to-leading-logarithm in the event shape.

Event shapes in e+e annihilation and deep inelastic scattering

“…These are referred to as non-global observables and NLL resummed predictions for them require that one account for coherent ensembles of energy-ordered large-angle gluons. This has so far been done only in the large-N C limit [33,53,65,[74][75][76] (for reviews see [77]), though progress is being made in extending this to finite N C [78]. To illustrate the impact of resummations we show in figure 1 the LO, NLO and resummed results for the thrust distribution.…”

“…Tests with Monte Carlo event generators which may indicate that any 'non-factorisation' is small [93] are not reliable, because the event generator used almost certainly does not contain the full 1-photon, 1-gluon matrix element. It is also to be noted that the isolation cuts on the photon will bias the distribution of the event shapes, in some cases [89,93] similarly to an event-shape energy-flow correlation [65,76]. Therefore we would argue that before relying on these data, one should at the very least compare the factorisation approximation with exact LO calculations, which can be straightforwardly obtained using packages such as Grace [111], CompHEP [112] or Amegic++ [113].…”

Jet mass spectra in Higgs boson plus one jet at next-to-next-to-leading logarithmic order

“…The first calculations were carried out for event shapes in e + e − → jets using hemisphere jet masses. Here factorization theorems are well established and calculations exist up to N 3 LL [15,19,21,[34][35][36][37][38]. In Refs.…”

Quark and Gluon Tagging at the LHC

“…The second, more continuous, category of observables includes jet mass, jet broadening [17], and the family of radial moments like girth [18], angularities [19], and the optimal moment which are described below. These tend to perform better at lower jet p T and for achieving high quark purity through harsh cuts.…”

“…Angularities [19,21] are one such example, where the p T and r are usually replaced by energy and angle. Angularities are often normalized by the jet mass rather than the jet p T , and we considered both normalizations.…”