SLIDE 1
POWER CORRECTIONS
FROM MILAN TO LHC
Gavin P . Salam, CERN Giuseppe Marchesini Memorial Meeting GGI, Florence, 19 May 2017
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A PIVOTAL ARTICLE
set out systematics of power corrections for almost any QCD observable “Wise Dispersive Method”
ELSEVIER Nuclear Physics B 469 (1996) 93-142
NUCLEAR PHYSICS B
Dispersive approach to power-behaved
- -k
contributions in QCD hard processes
Yu.L. Dokshitzer a,1, G. Marchesini b B.R. Webber c
a Theory Division, CERN, CIt-121! Geneva 23, Switzerland b Dipartimento di Fisica, Universit~ di Milano, and INFN, Sezione di Milano, haly c Cavendish Laboratory, University of Cambridge, UK Received 25 January 1996; accepted 18 March 1996
Abstract We consider power-behaved contributions to hard processes in QCD arising from non-pertur- bative effects at low scales which can be described by introducing the notion of an infrared- finite effective coupling. Our method is based on a dispersive treatment which embodies running coupling effects in all orders. The resulting power behaviour is consistent with expectations based
- n the operator product expansion, but our approach is more widely applicable. The dispersively
generated power contributions to different observables are given by (log-)moment integrals of a universal low-scale effective coupling, with process-dependent powers and coefficients. We analyze a wide variety of quark-dominated processes and observables, and show bow the power contributions are specified in lowest order by the behavioar of one-loop Feynman diagrams containing a gluon of small virtual mass. We discuss both collinearosafe observables (such as the e+e - total cross section and z hadronic width, DIS sum rules, e+e - event shape variables and the Drell-Yan K-factor) and collinear divergent quantities (such as DIS structure functions, e+e - fragmentation functions and the Drell-Yan cross section).
- 1. Introduction
Power-behaved contributions to hard collision observables are by now widely rec-
- gnized both as a serious difficulty in improving the precision of tests of perturbative
* Research supported in part by the UK Particle Physics and Astronomy Research Council and by the EC Programme "Human Capital and Mobility", Network "Physics at High Energy Colliders", contract CHRX- CT93-0357 (DG 12 COMA). E On leave from St. Petersburg Nuclear Physics Institute, Gatchina, St. Petersburg 188350, Russia. Elsevier Science B.V. PH S0550-3213(96)00155- 1
with process-dependent powers and coefficients. We analyse a wide variety of quark-dominated processes and observables, and show how the power contri- butions are specified in lowest order by the behaviour of one-loop Feynman diagrams containing a gluon of small virtual mass. We discuss both collinear safe observables (such as the e+e− total cross section and τ hadronic width, DIS sum rules, e+e− event shape variables and the Drell-Yan K-factor) and collinear divergent quantities (such as DIS structure functions, e+e− fragmen- tation functions and the Drell-Yan cross section).
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