HJets++ is a dedicated Matchbox plugin providing amplitudes for the calculation of electroweak Higgs plus jets production at NLO QCD. This library has been used in the calculation reported in 1308.2932. It provides a full calculation of \(pp\to h + n\) jets at \({\cal O}(\alpha^3\alpha_s^{n-2})\) for \(n=2,3,4\) at leading, and \(n=2,3\) at next-to-leading order QCD. All relevant topologies of either VBF or Higgs-Strahlung type are taken into account along with all interferences.

HJets++ features a simple build system and can be configured via:

./configure --with-herwig=/path/to/herwig/7

After make and make install the matrix elements are available to Herwig and can be used for the above mentioned processes by uncommenting the line:

read Matchbox/HJets.in

in the default LHC-Matchbox.in input file.

HiggsPairOL and HiggsPair

The HiggsPair* packages offer production of Higgs boson pairs via gluon fusion. HiggsPair uses M. Spira’s HPAIR code whereas HiggsPairOL uses the OpenLoops one-loop generator for the matrix elements. When using the latter, Herwig should be compiled with the option –with-openloops=.


This model describes leading-order Higgs boson pair production, either in the standard model or in D=6 effective field theory. The input file LHC-HH.in describes all the relevant options.

This was initially described in 1310.6877.


The model describs SM Higgs boson pair production, with the additional option of adding Higgs-Higgs+1 jet matrix elements merged to the parton shower via the MLM method. See 1401.0007 for a detailed description. The subdirectory input contains input files for leading order + parton shower and merged to 1-jet + parton shower, and the subdirectory rivet provides a Rivet Monte Carlo analysis for Higgs boson pairs.