title: Precision jet substructure from boosted event shapes.
abstract: Jet substructure has emerged as a critical tool for LHC searches, but studies so far have relied heavily on shower Monte Carlo simulations, which formally approximate QCD at the leading-log level. We demonstrate that systematic higher-order QCD computations of jet substructure can be carried out by boosting global event shapes by a large momentum Q and accounting for effects due to finite jet size, initial-state radiation (ISR), and the underlying event (UE) as 1/Q corrections. In particular, we compute the 2-subjettiness substructure distribution for boosted Z→qq[over ¯] events at the LHC at next-to-next-to-next-to-leading-log order. The calculation is greatly simplified by recycling known results for the thrust distribution in e(+)e(-) collisions. The 2-subjettiness distribution quickly saturates, becoming Q independent for Q > or approximately equal to 400 GeV. Crucially, the effects of jet contamination from ISR/UE can be subtracted out analytically at large Q without knowing their detailed form. Amusingly, the Q=∞ and Q=0 distributions are related by a scaling by e up to next-to-leading-log order.
authors.affiliation: Center for the Fundamental Laws of Nature, Harvard University, Cambridge, Massachusetts 02138, USA.
authors.forename: Ilya
authors.initials: I
authors.lastname: Feige
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Schwartz
authors.forename: Iain W
authors.initials: IW
authors.lastname: Stewart
authors.forename: Jesse
authors.initials: J
authors.lastname: Thaler