Two-to-three processes

Higher orders for higher multiplicity cross-sections

Contributions to three jet production through NNLO QCD

Multi-jet and photon production are a staple of Standard Model phenomenology, at the Large Hadron Collider. As more and more data is collected at the Large Hadron Collider and experimental analysis techniques improve, it is possible to measure processes with higher precision. This is also true for higher multiplicity processes with many produced particles or jets, for example three-jet production. Indeed, the experimental precision for many processes with three or more identified objects is already much higher than how precise the current 'industry standard', NLO QCD predictions, can currently calculate what data to expect for the Standard Model. The next level of precision are NNLO QCD predictions. They are often needed to reach similar precision as experimental data and to describe this data accurately and theoretically. These processes offer many phenomenological applications, such as extracting, and thus being able to look at, specific relevant values or process functions within these calculations, such as the strong coupling constant, or functions of photon fragmentation. They also improve estimates of how much background noise is captured alongside data.

The additional corrections at higher-order that differentiate NNLO from NLO QCD are an enormous challenge to compute. It is one of the edges of precision phenomenology. The demands on the efficiency and stability of the numerical computations are high. We use the STRIPPER framework for this. It uses a mathematical knack and sophisticated implementation to strip away parts of the calculations that can create computation problems, without compromising the reliability of the results. It has been used to compute several production processes found at the LHC where from two particles, three particles or jets are created. These are all the ones where any particles are photons, which have no mass. Jets, though they are many particles, can be surprisingly well described by an approximation without mass. All of the described processes are thus massless two-to-three productions.

  • Three-photon
  • Photon-pair plus jet
  • Photon plus jet pair
  • Three-jet
We work on constantly improving the STRIPPER framework to further increase computational efficiency. We also work to compute the necessary two-loop amplitudes, which are the defining step in the additional corrections at NNLO.

Multi-jet and photon production are a staple of Standard Model phenomenology at the Large Hadron Collider. As more and more data is collected at the Large Hadron Collider and experimental analysis techniques improve, measuring higher multiplicity processes, for example, three-jet production, with higher precision, is possible. Indeed, the experimental precision for many processes with three or more identified objects is already much higher than that of NLO QCD predictions, which are the 'industry standard'. NNLO QCD predictions are often needed to reach experimental precision and to describe the data accurately and theoretically. These processes offer many phenomenological applications, such as extracting the strong coupling constant, improving background estimates, and extracting photon fragmentation functions.

Computing the higher-order corrections for these processes is an enormous challenge and one of the edges of precision phenomenology. The demands on the efficiency and stability of the numerical computations are high. The STRIPPER framework has been used to compute all massless two-to-three production processes at the LHC:

  • Three-photon
  • Photon-pair plus jet
  • Photon plus jet pair
  • Three-jet
We work on computing the necessary two-loop amplitudes and constantly improving the STRIPPER framework to further increase computational efficiency.

Related publications

2023

  1. Isolated photon production in association with a jet pair through next-to-next-to-leading order in QCD
    Simon Badger ,  Michał Czakon ,  Heribertus Bayu Hartanto ,  Ryan Moodie ,  Tiziano Peraro ,  Rene Poncelet ,  and  Simone Zoia
    JHEP 10 071, 2023
    Arxiv:2304.06682

2023

  1. NNLO QCD corrections to event shapes at the LHC
    Manuel Alvarez ,  Josu Cantero ,  Michal Czakon ,  Javier Llorente ,  Alexander Mitov ,  and  Rene Poncelet
    JHEP 03 129, 2023
    Arxiv:2301.01086

2022

  1. Flavour anti-k_\textT algorithm applied to Wb\barb production at the LHC
    Heribertus Bayu Hartanto ,  Rene Poncelet ,  Andrei Popescu ,  and  Simone Zoia
    Sep 2022
    Arxiv:2209.03280

2022

  1. Next-to-next-to-leading order QCD corrections to Wbb\textasciimacron production at the LHC
    Heribertus Bayu Hartanto ,  Rene Poncelet ,  Andrei Popescu ,  and  Simone Zoia
    Phys. Rev. D 106 7 074016, 2022
    Arxiv:2205.01687

2021

  1. Next-to-Next-to-Leading Order Study of Three-Jet Production at the LHC
    Michal Czakon ,  Alexander Mitov ,  and  Rene Poncelet
    Phys. Rev. Lett. 127 15 152001, 2021
    [Erratum: Phys.Rev.Lett. 129, 119901 (2022), Erratum: Phys.Rev.Lett. 129, 119901 (2022)]
    Arxiv:2106.05331

2021

  1. NNLO QCD corrections to diphoton production with an additional jet at the LHC
    Herschel A. Chawdhry ,  Michal Czakon ,  Alexander Mitov ,  and  Rene Poncelet
    JHEP 09 093, 2021
    Arxiv:2105.06940

2021

  1. Two-loop leading-colour QCD helicity amplitudes for two-photon plus jet production at the LHC
    Herschel A. Chawdhry ,  Michal Czakon ,  Alexander Mitov ,  and  Rene Poncelet
    JHEP 07 164, 2021
    Arxiv:2103.04319

2021

  1. Two-loop leading-color helicity amplitudes for three-photon production at the LHC
    Herschel A. Chawdhry ,  Michal Czakon ,  Alexander Mitov ,  and  Rene Poncelet
    JHEP 06 150, 2021
    Arxiv:2012.13553

2020

  1. NNLO QCD corrections to three-photon production at the LHC
    Herschel A. Chawdhry ,  Micha L. Czakon ,  Alexander Mitov ,  and  Rene Poncelet
    JHEP 02 057, 2020
    Arxiv:1911.00479