Eur. Phys. J. C (2006) 47: 113-124
https://doi.org/10.1140/epjc/s2006-02552-4

Theoretical Physics

Infrared-safe definition of jet flavour

¹ Centre for Mathematical Sciences, DAMTP, Cambridge, CB3 0WA, UK
² Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK
³ University of Milano–Bicocca and INFN Sezione di Milano, Milano, Italy
⁴ LPTHE: Université Pierre et Marie Curie – Paris 6; Université Denis Diderot – Paris 7; CNRS, 75252, Paris, France
⁵ Theory Group, Fermilab, P.O. Box 500, Batavia, IL, USA
⁶ Theory Division, Physics Department, CERN, 1211, Geneva 23, Switzerland

^* e-mail: andrea.banfi@mib.infn.it

Received: 19 January 2006
Revised: 10 March 2006
Published online: 19 May 2006

Abstract

It is common, in both theoretical and experimental studies, to separately discuss quark and gluon jets. However, even at parton level, widely-used jet algorithms fail to provide an infrared-safe way of making this distinction. We examine the origin of the problem and propose a solution in terms of a new “flavour-k_t” algorithm. As well as being of conceptual interest this can be a powerful tool when combining fixed-order calculations with multi-jet resummations and parton showers. It also has applications to studies of heavy-quark jets.