This plugin implements an inclusive, spherically-invariant
generalised-kt jet algorithm for Deep Inelastic Scattering, defined in
the Breit frame.  This family of jet algorithms was introduced in
[arXiv:XXXX.YYYY](https://arxiv.org/abs/XXXX.YYYY) ("A generalised-kt
jet algorithm for Deep Inelastic Scattering", Melissa van Beekveld,
Silvia Ferrario Ravasio, Alexander Karlberg, Darcy Peake), with the
angular-ordered variant presented already in
[arXiv:2305.08645](https://arxiv.org/abs/2305.08645)
("Next-to-leading-logarithmic PanScales showers for Deep Inelastic
Scattering and Vector Boson Fusion", Melissa van Beekveld, Silvia
Ferrario Ravasio)

The family of algorithms is governed by a parameter $p>=0$.  The
distance between two pseudo-jets is given by $d_{ij} = 2
\min(E_i^{2p},E_j^{2p})(1-\cos(\theta_{ij}))$, while the distance with
a pseudo-jet and a beam is given by $d_{iB} = 2
E_i^{2p}(1-\cos(\theta_{iB}))$. 

The FJcontrib also implements a function called `sorted_by_zjet` that
orders the jets maximising the light-cone component along the original
struck quark momentum in the Breit frame.

The jet algorithm is invoked in a similar way to native FastJet
algorithms. We refer the user to [`example.cc`](example.cc) for a detailed example.

For bug reports, comments, or questions please send the authors an
email (see [`AUTHORS.md`](AUTHORS.md)).
