Introduction to Soft-Collinear Effective Theory

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: Jhep05(2016)117mentioning

confidence: 99%

Analytic boosted boson discrimination

Larkoski

Moult

Neill

2016

109

166

“…However, due to the mechanism of dynamical threshold enhancement [15,31], it is often the case that also observables sensitive to other regions of phase space receive their dominant contributions 1 See [16] for a first introduction to SCET.…”

Section: Jhep03(2016)124mentioning

confidence: 99%

Associated production of a top pair and a Higgs boson beyond NLO

Broggio

Ferroglia

Pecjak³

et al. 2016

Self Cite

118

We consider soft gluon emission corrections to the production of a top-antitop pair in association with a Higgs boson at hadron colliders. In particular, we present a softgluon resummation formula for this production process and gather all elements needed to evaluate it at next-to-next-to-leading logarithmic order. We employ these results to obtain approximate next-to-next-to-leading order (NNLO) formulas, and implement them in a bespoke parton-level Monte Carlo program which can be used to calculate the total cross section along with arbitrary differential distributions. We use this tool to study the phenomenological impact of the approximate NNLO corrections, finding that they increase the total cross section and the differential distributions which we evaluated in this work.

“…In order to verify it to NNLO, we first define expansion coefficients of the bare and renormalized functions as 8) and similarly for the component functions H S m and S m . Our definitions are such that bare coupling constant in d-dimensions is written as α 0μ 2 , whereμ 2 = µ 2 e γ E /(4π) is chosen to obtain results in the MS scheme.…”

Section: Jhep12(2016)018mentioning

confidence: 99%

Factorization for the light-jet mass and hemisphere soft function

Becher

Pecjak

Shao

2016

Self Cite

Many collider observables suffer from non-global logarithms not captured by standard resummation techniques. Classic examples are the light-jet mass event shape in the limit of small mass and the related hemisphere soft function. We derive factorization formulas for both of these and explicitly demonstrate that they capture all logarithms present at NNLO. These formulas achieve full scale separation and provide the basis for all-order resummations. A characteristic feature of non-global observables is that the soft radiation is driven by multi-Wilson-line operators, and the ones arising here map onto those relevant for the case of narrow-cone jet cross sections. Numerically, the contributions of non-global logarithms to resummed hemisphere-mass event shapes are sizeable.