Phenomenology of jet angularities at the LHC

Abstract

We compute resummed and matched predictions for jet angularities in hadronic dijet and Z+jet events with and without grooming the candidate jets using the SoftDrop technique. Our theoretical predictions also account for nonperturbative corrections from the underlying event and hadronisation through parton-to-hadron level transfer matrices extracted from dedicated Monte Carlo simulations with SHERPA. Thanks to this approach we can account for nonperturbative migration effects in both the angularities and the jet transverse momentum. We compare our predictions against recent measurements from the CMS experiment. This allows us to test the description of quark-and gluon-jet enriched phase-space regions separately. We supplement our study with SHERPA results based on the matching of NLO QCD matrix elements with the parton shower. Both theoretical predictions offer a good description of the data, within the experimental and theoretical uncertainties. The latter are however sizeable, motivating higher-accuracy calculations.

Event Generators for High-Energy Physics Experiments

“…RECOLA has been interfaced to several public Monte Carlo generators. In SHERPA [640], the interface [641] is fully general for NLO QCD and EW corrections and was used for several NLO computations [642][643][644][645][646][647][648]. A public interface to WHIZARD 2.4.1 exists [649], while an interface to HERWIG exists but is not yet public [650].…”

“…It allows the resummation of the recursive IRC safe observables of the original CAESAR formalism, as well as of event shapes including soft drop grooming in various settings [835,836]. The latest addition are (groomed) jet substructure observables, in particular jet angularities, in hadronic production processes [646,647]. The resummation of soft gluons around complicated color structures is automated using an interface to the matrix element generator COMIX [31].…”

“…Ref. [647] avoided this problem in the context of calculations of jet substructure observables by iterative re-clustering the constituents of an anti-k t jet with the BSZ algorithm, thus defining its flavor in an IR safe manner. This can contribute to the topic of quark-gluon discrimination that is of more general interest, see for example [592,596,[841][842][843][844][845][846], beyond the technical developments of event generators and resummation tools.…”

“…Resummed predictions can on the other hand largely benefit from event generator based studies of non-perturbative corrections. In [647], such a study was used to derive transition matrices, describing non-perturbative shifts simultaneously in the transverse momentum of a jet and in a jet substructure observable. For the Les Houches angularity [592,850,851], there is a major contribution in adding shifts in the angularity bins to the perturbative distribution, and a minor but significant effect of adding contributions from neighboring p T bins, which saturates when adding contributions from regions further away in p T .…”

Identification of b-jets using QCD-inspired observables

“…In particular, we use jet angularities [16][17][18] and the primary Lund Plane (pLP) [19] as inputs to train ML algorithms. These observables have been the target of recent measurements campaigns at the LHC [20][21][22][23] as well as of detailed theoretical investigation [24][25][26][27][28][29][30]. Therefore, jet angularities and pLP provide us with the opportunity to construct taggers that are, at the same time, efficient and robust.…”