Welcome to NJet project wiki

NJet is a library for multi-parton matrix elements up to two loops in massless QCD. NJet is based on the generalized unitarity program NGluon and uses QCDLoop/FF for scalar integrals and libqd for extended precision arithmetic. The two-loop finite remainders use PentagonFunctions++ for the integrals and Eigen for algebra.

1. About NJet
2. Getting started
3. Event generation with NJet+Sherpa
4. Physics results

News

• 15.9.2023 Version 3.1.2 is a small bug patch for 2L 3g2A.

• 15.1.2022 Version 3.1.1 is a patch to improve compatibility on macOS systems.

• 16.03.2022 Version 3.1.0 adds analytic two-loop leading-colour finite remainders for all five parton amplitudes. There have also been some changes to dependencies: QD is now strictly an external dependency, with versions >=2.3.23 supported. The required Eigen version is now >=3.4, and the required PentagonFunctions version is >=2.0.

• 21.06.2021 Version 3.0.1 fixes some bugs with the installation of the two-loop processes.

• 14.06.2021 Version 3.0.0 released, featuring two-loop matrix elements. Changes include: two-loop finite remainders provided for five gluons (leading colour) and gluon fusion to diphoton and gluon (full colour); analytic one-loop diphoton amplitudes added (2g2A, 3g2A); library of QCD infrared limit functions added; OneL0op one-loop scalar integral library supported, providing extended precision for one-loop integrals; and configure interface overhaul for faster builds. Version 3 is tracked on the njet3 branch, while master remains version 2. This release is available in the downloads section.

• 14.07.2020 Version 2.1.1 released, fixing a bug in setting Nf via the BLHA interface. Note that the order file parameter NJetNf of v2.0.0 has been replaced with SetParameter qcd(Nf).

• 16.06.2020 Version 2.1.0 released, adding support for Python 3. Now njet.py is compatible with Python >=3.2, while maintaining backwards compatibility with Python 2.7. Various other internal improvements of the Python code were also included.

• 05.05.2014 NJet version 2.0.0 with more processes has been released and is now available in the downloads section. It provides jets, W+jets, Z+jets, A+jets, AA+jets virtual matrix elements via BLHA2 interface. As well as leading/subleading colour, desymmetrized amplitudes, colour and spin-correlated trees. It also features significant speed improvement for 2- and 3-jet processes by utilizing analytic expressions for a selection of amplitudes.