Jet shapes with the broadening axis

Self Cite

109

166

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.

Section: Numerical Results and Comparison With Monte Carlomentioning

confidence: 99%

“…Throughout this section, all jets are defined using the e + e − anti-k T clustering metric [93,99] with the Winner-Take-All (WTA) recombination scheme [72,100]. To focus on the aspects of the factorization relevant to the jet substructure, we will present the factorization theorems for the specific case of e + e − → qq.…”

Section: Jhep05(2016)117mentioning

confidence: 99%

Analytic boosted boson discrimination

Larkoski

Moult

Neill

2016

Self Cite

109

166

“…Inter-jet radiation and in particular its response to the presence of a jet veto has also received a lot of attention both from the theoretical [53][54][55][56][57][58][59] and experimental [60][61][62][63] communities, primarily in the context of Higgs-boson studies [64][65][66][67][68][69][70]. All-order analytical calculations have been performed recently for an increasing number of jet-substructure observables, including jet masses [71][72][73][74], other jet shapes [75][76][77][78][79], sub-jet multiplicity [80] and grooming algorithms [81][82][83]. Recently, there has also been substantial progress towards achieving NNLL accuracy in threshold resummation for dijet production [84,85].…”

Section: Jhep02(2015)106mentioning

confidence: 99%

Soft evolution of multi-jet final states

Gerwick

Schumann

Höche

et al. 2015

We present a new framework for computing resummed and matched distributions in processes with many hard QCD jets. The intricate color structure of soft gluon emission at large angles renders resummed calculations highly non-trivial in this case. We automate all ingredients necessary for the color evolution of the soft function at next-toleading-logarithmic accuracy, namely the selection of the color bases and the projections of color operators and Born amplitudes onto those bases. Explicit results for all QCD processes with up to 2 → 5 partons are given. We also devise a new tree-level matching scheme for resummed calculations which exploits a quasi-local subtraction based on the Catani-Seymour dipole formalism. We implement both resummation and matching in the Sherpa event generator. As a proof of concept, we compute the resummed and matched transverse-thrust distribution for hadronic collisions.

“…One of the recently studied jet shape observable is the two-point energy correlation function C (β) 1 [27,45], which can be defined in the rest frame of a parton pair as…”

Section: Emission Propertymentioning

confidence: 99%

Evolution variable dependence of jet substructure

Sakaki

2015

Studies on jet substructure have evolved significantly in recent years. Jet substructure is essentially determined by QCD radiations and non-perturbative effects. Predictions of jet substructure are usually different among Monte Carlo event generators, and are governed by the parton shower algorithm implemented. For leading logarithmic parton shower, even though one of the core variables is the evolution variable, its choice is not unique. We examine evolution variable dependence of the jet substructure by developing a parton shower generator that interpolates between different evolution variables using a parameter α. Jet shape variables and associated jet rates for quark and gluon jets are used to demonstrate the α-dependence of the jet substructure. We find angular ordered shower predicts wider jets, while relative transverse momentum (p ⊥ ) ordered shower predicts narrower jets. This is qualitatively in agreement with the missing phase space of p ⊥ ordered showers. Such difference can be reduced by tuning other parameters of the showering algorithm, especially in the low energy region, while the difference tends to increase for high energy jets.