A General Algorithm for Calculating Jet Cross Sections in NLO QCD
Stefano Catani (Firenze) and Michael H. Seymour (CERN)
Abstract
We present a new general algorithm for calculating arbitrary jet cross
sections in arbitrary scattering processes to next-to-leading accuracy in
perturbative QCD. The algorithm is based on the subtraction method. The key
ingredients are new factorization formulae, called dipole formulae, which
implement in a Lorentz covariant way both the usual soft and collinear
approximations, smoothly interpolating the two. The corresponding dipole
phase space obeys exact factorization, so that the dipole contributions to
the cross section can be exactly integrated analytically over the whole of
phase space. We obtain explicit analytic results for any jet observable in
any scattering or fragmentation process in lepton, lepton-hadron or
hadron-hadron collisions. All the analytical formulae necessary to construct
a numerical program for next-to-leading order QCD calculations are provided.
The algorithm is straightforwardly implementable in general purpose Monte
Carlo programs.
Eventually I am planning to set up quite a few different formats of this
paper. So far I have:
Postscript.
Since submitting the original version, we have found several minor misprints.
To save reprinting the whole postscript file, here is a
list of them. We also added a
note to the end of the paper.
Since the publication of the paper, we have found an error in the definition
of the Lorentz boosts employed for cross sections with 2 or more identified
partons (sections 5.5 and 5.6). As a result, we have submitted an
erratum to Nuclear Physics.
The version above is corrected accordingly.
At one time we had the idea that Appendix C could act as a sort of index,
by numbering the equations according to the numbering in the main text.
Although we didn't do that for the final version, it could be useful for
anyone making a numerical implementation using our method. So there is
a copy here for anyone who wants it.
There is also a shorter description of the algorithm in
Letter form.
You might also be interested in the
programs
that are based on it.
Mike Seymour