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We present differential cross sections for the production of top-quark pairs in conjunction with up to two jets, computed at next-to leading order in perturbative QCD and consistently merged with a parton shower in the Sherpa+OpenLoops…

High Energy Physics - Phenomenology · Physics 2015-07-01 Stefan Höche , Frank Krauss , Philipp Maierhoefer , Stefano Pozzorini , Marek Schonherr , Frank Siegert

A Monte-Carlo event-generator has been developed which is dedicated to simulate electron-positron annihilations. Especially a new approach for the combination of matrix elements and parton showers ensures the independence of the…

High Energy Physics - Phenomenology · Physics 2017-08-23 R. Kuhn , A. Schaelicke , F. Krauss , G. Soff

We develop a forward branching phase-space generator for use in next-to-leading order parton level event generators. By performing 2 -> 3 branchings from a fixed jet phase-space point, all bremsstrahlung events contributing to the given jet…

High Energy Physics - Phenomenology · Physics 2011-06-27 Walter T. Giele , Gerben C. Stavenga , Jan-Christopher Winter

We study the logarithmic accuracy of angular-ordered parton showers by considering the singular limits of multiple emission matrix elements. This allows us to consider different choices for the evolution variable and propose a new choice…

High Energy Physics - Phenomenology · Physics 2020-03-27 Gavin Bewick , Silvia Ferrario Ravasio , Peter Richardson , Michael H. Seymour

We investigate the effects of combining next-to-leading order QCD results with parton-shower effects in $W^+W^-jj$ production via vector-boson fusion including leptonic decays. Using the Herwig 7 framework interfaced to VBFNLO 3, we compare…

High Energy Physics - Phenomenology · Physics 2016-07-04 Michael Rauch , Simon Plätzer

We compare different procedures for combining fixed-order tree-level matrix-element generators with parton showers. We use the case of W-production at the Tevatron and the LHC to compare different implementations of the so-called CKKW and…

We propose a new way to impose four-momentum conservation on timelike parton-shower branchings, allowing for recoil to be imparted not only to individual partons but also to groups of partons, "jets". In this work we present an explicit…

High Energy Physics - Phenomenology · Physics 2025-12-09 Jack Helliwell , Ludovic Scyboz , Peter Skands

We consider a model of transverse momentum production in which non-perturbative smearing takes place throughout the perturbative evolution, by a simple modification to an initial state parton shower algorithm. Using this as the important…

High Energy Physics - Phenomenology · Physics 2009-02-18 Stefan Gieseke , Michael H. Seymour , Andrzej Siodmok

We compare different procedures for combining fixed-order tree-level matrix element generators with parton showers. We use the case of W-production at the Tevatron and the LHC to compare different implementations of the so-called CKKW…

High Energy Physics - Phenomenology · Physics 2007-05-23 Stefan Hoeche , Frank Krauss , Nils Lavesson , Leif Lonnblad , Michelangelo Mangano , Andreas Schaelicke , Steffen Schumann

We formulate PanScales parton showers for hadron collisions so as to achieve next-to-leading logarithmic (NLL) accuracy across a broad set of observables. We do so specifically for colour singlet production. Relative to the existing…

High Energy Physics - Phenomenology · Physics 2022-11-23 Melissa van Beekveld , Silvia Ferrario Ravasio , Gavin P. Salam , Alba Soto-Ontoso , Gregory Soyez , Rob Verheyen

The second-order QCD matrix elements give a very good agreement with experimental data on the angular distributions of the four-jet events in e+e- collisions at the Z0 resonance energy. Unfortunately the description of the sub-jet structure…

High Energy Physics - Phenomenology · Physics 2007-05-23 Johan André

One of the most important developments in Monte Carlo simulation of collider events for the LHC has been the arrival of schemes and codes for matching of parton showers to matrix elements calculated at next-to-leading order in the QCD…

High Energy Physics - Phenomenology · Physics 2017-12-21 Andy Buckley , Debottam Bakshi Gupta

We present a full-fledged antenna shower for hadron collisions in the Vincia framework and focus on initial state radiation. The current version of the shower is limited to massless QCD partons and colourless resonances. As a…

High Energy Physics - Phenomenology · Physics 2016-04-20 Nadine Fischer , Peter Skands

We study in this paper the production, in hadronic collisions, of final states with W gauge bosons, heavy quark pairs and n extra jets (with n up to 4). The complete partonic tree-level QCD matrix elements are evaluated using the ALPHA…

High Energy Physics - Phenomenology · Physics 2008-11-26 Michelangelo L. Mangano , Mauro Moretti , Roberto Pittau

We formulate some first fundamental elements of an approach for assessing the logarithmic accuracy of parton-shower algorithms based on two broad criteria: their ability to reproduce the singularity structure of multi-parton matrix…

High Energy Physics - Phenomenology · Physics 2020-02-27 Mrinal Dasgupta , Frédéric A. Dreyer , Keith Hamilton , Pier Francesco Monni , Gavin P. Salam

In recent times the algorithms for the simulation of hadronic collisions have been subject to two substantial improvements: the inclusion, within parton showering, of exact higher order tree level matrix elements (MEPS) and, separately,…

High Energy Physics - Phenomenology · Physics 2015-03-14 Keith Hamilton , Paolo Nason

We present a method for sampling singular functions defined on (nested) multi-particle phase spaces, based on a generalisation of parton-shower phase-space generation techniques. At the heart of the method are three key ingredients: 1) the…

High Energy Physics - Phenomenology · Physics 2025-08-12 Javira Altmann , Hai Tao Li , Ludovic Scyboz , Peter Skands

We apply for the first time the Flow Matching method to the problem of phase-space sampling for event generation in high-energy collider physics. By training the model to remap the random numbers used to generate the momenta and helicities…

High Energy Physics - Phenomenology · Physics 2025-06-25 Enrico Bothmann , Timo Janßen , Max Knobbe , Bernhard Schmitzer , Fabian Sinz

A particle method for reproducing the phase space of collisionless stellar systems is described. The key idea originates in Liouville's theorem which states that the distribution function (DF) at time t can be derived from tracing necessary…

Astrophysics · Physics 2009-10-30 Shunsuke Hozumi

The theoretical treatment of jet quenching lacks a full description of the interplay between vacuum-like emissions, usually formulated in momentum space, and medium induced ones that demand an interface with a space-time picture of the…

High Energy Physics - Phenomenology · Physics 2024-02-16 Carlota Andrés , Liliana Apolinário , Néstor Armesto , André Cordeiro , Fabio Dominguez , José Guilherme Milhano