Analytic boosted boson discrimination

Abstract

Observables which discriminate boosted topologies from massive QCD jets are of great importance for the success of the jet substructure program at the Large Hadron Collider. Such observables, while both widely and successfully used, have been studied almost exclusively with Monte Carlo simulations. In this paper we present the first all-orders factorization theorem for a two-prong discriminant based on a jet shape variable, D 2 , valid for both signal and background jets. Our factorization theorem simultaneously describes the production of both collinear and soft subjets, and we introduce a novel zero-bin procedure to correctly describe the transition region between these limits. By proving an all orders factorization theorem, we enable a systematically improvable description, and allow for precision comparisons between data, Monte Carlo, and first principles QCD calculations for jet substructure observables. Using our factorization theorem, we present numerical results for the discrimination of a boosted Z boson from massive QCD background jets. We compare our results with Monte Carlo predictions which allows for a detailed understanding of the extent to which these generators accurately describe the formation of two-prong QCD jets, and informs their usage in substructure analyses. Our calculation also provides considerable insight into the discrimination power and calculability of jet substructure observables in general.

A complete basis of helicity operators for subleading factorization

“…In addition to collinear and soft modes, these effective field theories typically contain (multiple) collinear-soft modes, which exhibit both a collinear, and a soft scaling. Such effective field theories have been used, for example, for the calculation [101] of the D 2 [102] jet substructure observable. While subleading power corrections to SCET + theories have not been studied, we wish to emphasize that our helicity operator approach extends also straightforwardly to such theories.…”

Improved jet substructure methods: Y-splitter and variants with grooming

“…[8,12]. Analytical calculations have also been performed for the SoftDrop method [13][14][15] and for radiation constraining jet shapes [16,17] based on the N-subjettiness class of variables [18] and energy correlation functions (ECFs) [19]. These calculations have enabled a much more detailed and robust understanding of jet substructure methods than was possible with purely numerical studies from Monte Carlo event generators.…”

“…However it is crucial to impose the Y-splitter constraint on the plain jet instead of the groomed jet, otherwise one only gets a much smaller Sudakov suppression of the QCD background. 16 We should however stress that subleading corrections sometimes come with several transition points in the mass distribution, which can be an issue for practical applications in an experimental context.…”

Threshold and Jet Radius Joint Resummation for Single-Inclusive Jet Production

“…Because of the fact that the softcollinear radiation can resolve the splitting details of the collinear radiation inside the signal jet, one has to perform an infinite sum over the collinear splitting history inside the jet and keep the angular correlations between the jet and softcollinear radiation which account for the nonglobal logarithms (NGLs) [40], as addressed in Refs. [34,[41][42][43]. We note that the signal-jet and the soft-collinear functions can be viewed as the threshold limit of the semi-inclusive jet function [10,13].…”