27 f(-p1) + f(-p2) → W-(→ e-(p3) + ν(p4)) + f(p5) + f(p6)

27.1 W + 2 jets production, processes 22,27

This process represents the production of a W boson and 2 jets, where the W boson decays leptonically. The calculation may be performed up to NLO, as detailed below. Virtual amplitudes are taken from ref. [1]. For more details on this calculation, please see Refs. [2, 3].

For these processes (and also for Z + 2 jet production, nproc=44,46) the next-to-leading order matrix elements are particularly complex and may be divided into two groups. The division is according to the lowest order diagrams from which they originate:

  1. Diagrams involving two external quark lines and two external gluons, the “Gflag” contribution. The real diagrams in this case thus involve three external gluons.

  2. Diagrams where all four external lines are quarks, the “Qflag” contribution. The real diagrams in this case involve only one gluon.

By specifying Gflag and Qflag in the file input.ini one may select one of these options at a time. The full result may be obtained by straightforward addition of the two individual pieces, with no meaning attached to either piece separately. The default is that both of these are set to .true. simultaneously.

Virtual amplitudes are taken from ref. [1].

When removebr is true, the W boson does not decay.

27.2 Plotter

nplotter_Wjets.f is the default plotting routine.

27.3 Example input and output file(s)

input27.ini process27.out

References

[1]    Z. Bern, L.J. Dixon and D.A. Kosower, One loop amplitudes for e+ e- to four partons, Nucl. Phys. B513 (1998) 3 [hep-ph/9708239].

[2]    J.M. Campbell and R.K. Ellis, Next-to-Leading Order Corrections to W+ 2 jet and Z+ 2 Jet Production at Hadron Colliders, Phys. Rev. D 65 (2002) 113007 [hep-ph/0202176].

[3]    J.M. Campbell, R.K. Ellis and D.L. Rainwater, Next-to-leading order QCD predictions for W + 2 jet and Z + 2 jet production at the CERN LHC, Phys. Rev. D 68 (2003) 094021 [hep-ph/0308195].