Power corrections to event shapes with mass-dependent operators
Author(s)Thaler, Jesse; Barreda, Vicent Mateu; Stewart, Iain W
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We introduce an operator depending on the “transverse velocity” r that describes the effect of hadron masses on the leading 1/Q power correction to event-shape observables. Here, Q is the scale of the hard collision. This work builds on earlier studies of mass effects by Salam and Wicke [ J. High Energy Phys. 2001 061 ()] and of operators by Lee and Sterman [ Phys. Rev. D 75 014022 (2007)]. Despite the fact that different event shapes have different hadron mass dependence, we provide a simple method to identify universality classes of event shapes whose power corrections depend on a common nonperturbative parameter. We also develop an operator basis to show that at a fixed value of Q, the power corrections for many classic observables can be determined by two independent nonperturbative matrix elements at the 10% level. We compute the anomalous dimension of the transverse velocity operator, which is multiplicative in r and causes the power correction to exhibit nontrivial dependence on Q. The existence of universality classes and the relevance of anomalous dimensions are reproduced by the hadronization models in Pythia 8 and Herwig++, though the two programs differ in the values of their low-energy matrix elements.
DepartmentMassachusetts Institute of Technology. Department of Physics; Massachusetts Institute of Technology. Laboratory for Nuclear Science
Physical Review D
American Physical Society
Mateu, Vicent, Iain W. Stewart, and Jesse Thaler. “Power Corrections to Event Shapes with Mass-dependent Operators.” Physical Review D 87.1 (2013).
Final published version