We discuss the theoretical bases that underpin the automation of the computations of tree-level and next-to-leading order cross sections, of their matching to parton shower simulations, and of the merging of matched samples that differ by light-parton multiplicities. We present a computer program, MadGraph5 aMC@NLO, capable of handling all these computations — parton-level fixed order, shower-matched, merged — in a unified framework whose defining features are flexibility, high level of parallelisation, and human intervention limited to input physics quantities. We demonstrate the potential of the program by presenting selected phenomenological applications relevant to the LHC and to a 1-TeV e + e − collider. While next-to-leading order results are restricted to QCD corrections to SM processes in the first public version, we show that from the user viewpoint no changes have to be expected in the case of corrections due to any given renormalisable Lagrangian, and that the implementation of these are well under way.

/pdf/the-automated-computation-of-tree-level-and-next-to-leading-4etm0g6w46.pdf

The automated computation of tree-level and next-to-leading order differential cross sections, and their matching to parton shower simulations

The aim of this work is to describe in detail the POWHEG method, first suggested by one of the authors, for interfacing parton-shower generators with NLO QCD computations. We describe the method in its full generality, and then specify its features in two subtraction frameworks for NLO calculations: the Catani-Seymour and the Frixione-Kunszt-Signer approach. Two examples are discussed in detail in both approaches: the production of hadrons in e+e− collisions, and the Drell-Yan vector-boson production in hadronic collisions.

Matching NLO QCD computations with Parton Shower simulations: the POWHEG method

In this work we illustrate the POWHEG BOX, a general computer code framework for implementing NLO calculations in shower Monte Carlo programs according to the POWHEG method. Aim of this work is to provide an illustration of the needed theoretical ingredients, a view of how the code is organized and a description of what a user should provide in order to use it.

/pdf/a-general-framework-for-implementing-nlo-calculations-in-33rdilxwli.pdf

A general framework for implementing NLO calculations in shower Monte Carlo programs: the POWHEG BOX

https://cds.cern.ch/record/303326/files/arXiv:hep-ph_9605323.pdf

A general algorithm for calculating jet cross sections in NLO QCD

We discuss the theoretical bases that underpin the automation of the computations of tree-level and next-to-leading order cross sections, of their matching to parton shower simulations, and of the merging of matched samples that differ by light-parton multiplicities. We present a computer program, MadGraph5_aMC@NLO, capable of handling all these computations -- parton-level fixed order, shower-matched, merged -- in a unified framework whose defining features are flexibility, high level of parallelisation, and human intervention limited to input physics quantities. We demonstrate the potential of the program by presenting selected phenomenological applications relevant to the LHC and to a 1-TeV $e^+e^-$ collider. While next-to-leading order results are restricted to QCD corrections to SM processes in the first public version, we show that from the user viewpoint no changes have to be expected in the case of corrections due to any given renormalisable Lagrangian, and that the implementation of these are well under way.

/pdf/the-automated-computation-of-tree-level-and-next-to-leading-ug7t6p602g.pdf

Three-jet cross sections to next-to-leading order

One- and two-jet inclusive quantities in hadron collisions have already been calculated to next-to-leading order accuracy, using both the subtraction and the cone method Since the one-loop corrections have recently been obtained for all five-parton amplitudes, three-jet inclusive quantities can also be predicted to next-to-leading order The subtraction method presented in the literature is based on a systematic use of boost-invariant kinematical variables, and therefore its application to three-jet production is quite cumbersome In this paper we re-analyze the subtraction method and point out the advantage of using angle and energy variables This leads to simpler results and it has complete generality, extending its validity to $n$-jet production The formalism is also applicable to $n$-jet production in $e^+e^-$ annihilation and in photon-hadron collisions All the analytical results necessary to construct an efficient numerical program for next-to-leading order three-jet inclusive quantities in hadroproduction are given explicitly As new analytical result, we also report the collinear limits of all the two-to-four processes

tendees were early career researchers (graduate students or postdoctoral researchers, and the majority of participants (>90%) attended in-person. While observing the COVID-19 safety protocols on-site at LBNL, the overwhelming feeling of the week was excitement to be back at a conference again, face to face. The outdoor tent (with excellent ventilation) for meals and breaks was constantly occupied, with small groups of collaborators discussing their upcoming work, new collaborations forming, and much coffee being consumed. We were thrilled to have the opportunity to host NS2022, and thankful for support from our vendor sponsors Berkeley Nucleonics Corp., CAEN Technologies Inc., Mirion Technologies, Ortec/Ametek, PHDS, SkuTek, and XIA. We also have to thank the LBNL operations and security teams for logistical support, and the team within NSD for all of their work. The COVID-19 pandemic presented an unusual challenge, but one NS2022 overcame readily. Additional information about the NS2022 conference is available at https://conferences.lbl.gov/event/212/. The next installment of the Nuclear Structure series is planned for 2024, to be hosted by Argonne National Laboratory.

PSI2022: Physics of Fundamental Symmetries and Interactions at the Paul Scherrer Institut

Lange galt das Myon als Exot, heute wird es als hochsensitive Sonde genutzt, etwa für die Suche nach Neuer Physik.

Who ordered that?

Radiative corrections are crucial for modern high-precision physics experiments, and are an area of active research in the experimental and theoretical community. Here we provide an overview of the state of the field of radiative corrections with a focus on several topics: lepton-proton scattering, QED corrections in deep-inelastic scattering, and in radiative light-hadron decays. Particular emphasis is placed on the two-photon exchange, believed to be responsible for the proton form-factor discrepancy, and associated Monte-Carlo codes. We encourage the community to continue developing theoretical techniques to treat radiative corrections, and perform experimental tests of these corrections.

A. Signer

Papers

Three-jet cross sections to next-to-leading order

Three-jet cross sections to next-to-leading order

PSI2022: Physics of Fundamental Symmetries and Interactions at the Paul Scherrer Institut

Who ordered that?

Radiative Corrections: From Medium to High Energy Experiments