Sudakov Safety in Perturbative QCD

By A. Larkoski, S. Marzani, Jesse Thaler. 2015

163 citations recorded by the source corpus.

Traditional calculations in perturbative quantum chromodynamics (pQCD) are based on an order-by-order expansion in the strong coupling ${\ensuremath{\alpha}}_{s}$. Observables that are calculable in this way are known as ``safe.'' Recently, a class of unsafe observables was discovered that do not have a valid ${\ensuremath{\alpha}}_{s}$ expansion but are nevertheless calculable in pQCD using all-orders resummation. These observables are called ``Sudakov safe'' since singularities at each ${\ensuremath{\alpha}}_{s}$ order are regulated by an all-orders Sudakov form factor. In this paper, we give a concrete definition of Sudakov safety based on conditional probability distributions, and we study a one-parameter family of momentum sharing observables that interpolate between the safe and unsafe regimes. The boundary between these regimes is particularly interesting, as the resulting distribution can be understood as the ultraviolet fixed point of a generalized fragmentation function, yielding a leading behavior that is independent of ${\ensuremath{\alpha}}_{s}$.

Subfields: Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/5510d1ceb8e6886a51d42c98588ec7965aafd385

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In Nuclear and High Energy Physics

Citations in the corpus

Energy flow networks: deep sets for particle jets (2018, background): “Ratios of IRC-safe observables are not necessarily IRC safe [99, 100] since division is discontinuous at zero.”
Energy flow polynomials: a complete linear basis for jet substructure (2017, background): “For the N -subjettiness ratios, the regression performance depends on whether the observable is IRC safe or only Sudakov safe [82, 83].”
Les Houches 2017: Physics at TeV Colliders Standard Model Working Group Report (2017, background): “For β ≥ 0, this observable is Sudakov safe [823,824] on QCD jets.”
Analytic boosted boson discrimination (2015, methodology): “This property is referred to as Sudakov safety [70, 73].”
Jet substructure at the Large Hadron Collider: A review of recent advances in theory and machine learning (2017, methodology): “The study of Sudakov safe observables has, to this point, relied on the use of a formulation in terms of standard IRC safe observables to which the theoretical techniques discussed above do apply [135].”
Medium response in JEWEL and its impact on jet shape observables in heavy ion collisions (2017, methodology): “J H E P 0 7 ( 2 0 1 7 ) 1 4 1 related to the Altarelli-Parisi splitting function [49].”