hoppetv2 release note Alexander Karlberg, Paolo Nason, Gavin Salam, Giulia Zanderighi, Frédéric Dreyer European Physical Journal C, 2026 We document the three main new features in the v2 release series of the hoppet parton distribution function evolution code, specifically support for N $$^3$$ 3 LO QCD evolution in the variable flavour number scheme, for the determination of hadronic structure functions for massless quarks up to N $$^3$$ 3 LO, and for QED evolution to an accuracy phenomenologically equivalent to NNLO QCD. Additionally we describe a new Python interface, CMake build option, functionality to save a hoppet table as an LHAPDF grid and update our performance benchmarks, including optimisations in interpolating PDF tables.
Logarithmically-accurate and positive-definite NLO shower matching Melissa van Beekveld, Silvia Ferrario Ravasio, Jack Helliwell, Alexander Karlberg, Gavin P. Salam, Ludovic Scyboz, Alba Soto-Ontoso, Gregory Soyez, Silvia Zanoli Journal of High Energy Physics, 2025 We present methods to achieve NLL+NLO accurate parton showering for processes with two coloured legs: neutral- and charged-current Drell-Yan, and Higgs production in pp collisions, as well as DIS and e + e − to jets. The methods include adaptations of existing approaches, as well as a new NLO matching scheme, ESME, that is positive-definite by construction. Our implementations of the methods within the PanScales framework yield highly competitive NLO event generation speeds. We validate the fixed-order and combined resummation accuracy with tests in the limit of small QCD coupling and briefly touch on phenomenological comparisons to standard NLO results and to Drell-Yan data. The progress reported here is an essential step towards showers with logarithmic accuracy beyond NLL for processes with incoming hadrons.
An event generator for neutrino-induced deep inelastic scattering and applications to neutrino astronomy Silvia Ferrario Ravasio, Rhorry Gauld, Barbara Jäger, Alexander Karlberg, Giulia Zanderighi European Physical Journal C, 2025 We extend the recently presented, fully exclusive, next-to-leading-order accurate event generator for the simulation of massless neutral- and charged-current deep inelastic scattering (DIS) to the case of incoming neutrinos. The generator can be used to study neutrino-nucleon interactions at (ultra) high energies, and is relevant for a range of fixed-target collider experiments and large-volume neutrino detectors, investigating atmospheric and astrophysical neutrinos. The matching with multi-purpose event generators such as is performed with the method, and accounts for parton showering and non-perturbative effects such as hadronization. This makes it possible to investigate higher-order perturbative corrections to realistic observables, such as the distribution of charged particles. To illustrate the capabilities of the code we provide predictions for several differential distributions in fixed-target collisions for neutrino energies up to $$1~\\textrm{PeV} $$ 1 PeV .
Precision tools for the simulation of double-Higgs production via vector-boson fusion Barbara Jäger, Alexander Karlberg, Simon Reinhardt Journal of High Energy Physics, 2025 We present two precision tools for the simulation of Higgs-pair production via vector-boson fusion in the kappa framework for the parameterization of non-standard Higgs couplings. A new implementation of the process is developed in the framework of the POWHEG BOX program that can be used to provide predictions at the next-to-leading order (NLO) of QCD matched to parton showers (PS). In addition, the existing proVBFHH program for the computation of next-to-next-to-leading order (NNLO) QCD and next-to-next-to-next-to-leading order QCD corrections is extended to account for values of the Higgs couplings different from the expectation of the Standard Model. We systematically compare and analyse predictions obtained with the two programs and find that the NLO+PS predictions provide a good approximation of the NNLO results for observables of the tagging jets and Higgs bosons. The results turn out to be very sensitive to the values of the modified Higgs couplings. Finally we study the non-factorizable NNLO QCD corrections to the process in the presence of anomalous couplings. We find that the size of the non-factorizable corrections is very sensitive to the anomalous couplings.
New Standard for the Logarithmic Accuracy of Parton Showers Melissa van Beekveld, Mrinal Dasgupta, Basem Kamal El-Menoufi, Silvia Ferrario Ravasio, Keith Hamilton, Jack Helliwell, Alexander Karlberg, Pier Francesco Monni, Gavin P. Salam, Ludovic Scyboz, Alba Soto-Ontoso, Gregory Soyez Physical Review Letters, 2025 We report on a major milestone in the construction of logarithmically accurate final-state parton showers, achieving next-to-next-to-leading-logarithmic (NNLL) accuracy for the wide class of observables known as event shapes. The key to this advance lies in the identification of the relation between critical NNLL analytic resummation ingredients and their parton-shower counterparts. Our analytic discussion is supplemented with numerical tests of the logarithmic accuracy of three shower variants for more than a dozen distinct event-shape observables in Z→qq¯ and Higgs→gg decays. The NNLL terms are phenomenologically sizeable, as illustrated in comparisons to data. Published by the American Physical Society 2025
Benchmark of deep-inelastic-scattering structure functions at Oαs3 Valerio Bertone, Alexander Karlberg European Physical Journal C, 2024 We present a benchmark comparison of the massless inclusive deep-inelastic-scattering (DIS) structure functions up to $$\\mathcal {O}(\\alpha _s ^3)$$ O ( α s 3 ) in perturbative QCD. The comparison is performed using the codes apfel++ and hoppet within the framework of the variable-flavour-number scheme and over a broad kinematic range relevant to the extraction of parton distribution functions. We provide results for both the single structure functions and the reduced cross sections in both neutral- and charged-current DIS. Look-up tables for future reference are included, and we also release the code used for the benchmark.
Two-loop anomalous dimensions for small-R jet versus hadronic fragmentation functions Melissa van Beekveld, Mrinal Dasgupta, Basem Kamal El-Menoufi, Jack Helliwell, Alexander Karlberg, Pier Francesco Monni Journal of High Energy Physics, 2024 We study the collinear fragmentation of highly energetic jets defined with a small jet radius. In particular, we investigate how the corresponding fragmentation functions differ from their hadronic counterpart defined in the common $$ \\overline{\\textrm{MS}} $$ MS ¯ scheme. We find that the anomalous dimensions governing the perturbative evolution of the two fragmentation functions differ starting at the two loop order. We compute for the first time the new anomalous dimensions at two loops and confirm our predictions by comparing the inclusive small-R jet spectrum against a fixed order perturbative calculation at $$ \\mathcal{O} $$ O ($$ {\\alpha}_s^2 $$ α s 2 ). To investigate the dependence of the anomalous dimension on the kinematic cutoff variable, we study the fragmentation functions of Cambridge jets defined with a transverse momentum cutoff as opposed to an angular cutoff R. We further study the evolution of the small-R fragmentation function with an alternative cutoff scale, proportional to zR, representing the maximum possible transverse momentum of emissions within a jet. In these cases we find that the two-loop anomalous dimensions coincide with the $$ \\overline{\\textrm{MS}} $$ MS ¯ DGLAP ones, highlighting a correspondence between the $$ \\overline{\\textrm{MS}} $$ MS ¯ scheme and a transverse-momentum cutoff.
QCD effects in electroweak WZjj production at current and future hadron colliders B. Jäger, A. Karlberg, S. Reinhardt European Physical Journal C, 2024 We present an update of an existing implementation of WZjj production via vector-boson scattering in the framework of the program. In particular, previously unavailable semi-leptonic and fully hadronic decay modes of the intermediate vector bosons are provided, and operators of dimension six in an effective-field theory approach to account for physics beyond the Standard Model in the electroweak sector are included. For selected applications phenomenological results are provided to illustrate the capabilities of the new program. The impact of the considered dimension-six operators on experimentally accessible distributions is found to be small for current LHC energies, but enhanced in the kinematic reach of a potential future hadron collider with an energy of 100 TeV. The relevance of fully accounting for spin correlations and off-shell effects in the decay system is explored by a comparison with results obtained with the tool that are based on an approximate treatment of the leptonic final state resulting from vector boson scattering processes. For selected semi-leptonic and hadronic decay modes we demonstrate the sensitivity of realistic signal selection procedures on QCD corrections and parton-shower effects.
Event generators for high-energy physics experiments J. M. Campbell, M. Diefenthaler, T. J. Hobbs, Stefan Höche, Joshua Isaacson, Felix Kling, Stephen Mrenna, J. Reuter, S. Alioli, J. R. Andersen, C. Andreopoulos, A. M. Ankowski, Elke Caroline Aschenauer, A. Ashkenazi, M. D. Baker, Joshua L. Barrow, Melissa van Beekveld, Gavin Bewick, S. Bhattacharya, Christian Bierlich, Enrico Bothmann, P. Bredt, A. Broggio, Andy Buckley, A. Butter, Jonathan Mark Butterworth, E. P. Byrne, Carlo Carloni-Calame, Smita Chakraborty, X. Chen, M. Chiesa, J. T. Childers, J. Cruz-Martinez, J. Currie, N. Darvishi, M. Dasgupta, A. Denner, F. A. Dreyer, S. Dytman, Basem Kamal El-Menoufi, Tim Engel, Silvia Ferrario Ravasio, Daniel Figueroa, L. Flower, J. R. Forshaw, Rikkert Frederix, Alex Friedland, Stefano Frixione, H. Gallagher, K. Gallmeister, Simon Gardiner, Rhorry Gauld, Jonathan Gaunt, A. Gavardi, T. Gehrmann, Aude Gehrmann-De Ridder, Leif Gellersen, Walter Giele, Stefan Gieseke, Francesco Giuli, E. W. N. Glover, Massimiliano Grazzini, A. Grohsjean, Christian Gütschow, Keith Hamilton, T. Han, R. Hatcher, G. Heinrich, Ilkka Helenius, O. Hen, Valentin Hirschi, M. Höfer, J. Holguin, Alexander Huss, Philip Ilten, Stanislaw Jadach, A. Jentsch, S. P. Jones, W. Ju, Stefan Kallweit, Alexander Karlberg, T. Katori, Matthias Kerner, C. Kilian, M. M. Kirchgaeßer, S. Klein, Max Knobbe, Claudius Krause, Frank Krauss, J. Lang, J.-N Lang, G. Lee, S. W. Li, M. A. Lim, J. M. Lindert, D. Lombardi, Leif Lönnblad, M. Löschner, N. Lurkin, Y. Ma, P. Machado, Vitaly Magerya, A. Maier, I. Majer, Fabio Maltoni, M. Marcoli, G. Marinelli, M. R. Masouminia, Pierpaolo Mastrolia, Olivier Mattelaer, J. Mazzitelli, Josh McFayden, Rok Medves, P. Meinzinger, J. Mo, Pier Francesco Monni, Guido Montagna, T. Morgan, U. Mosel, Benjamin Nachman, Pavel Nadolsky, R. Nagar, Zoltan Nagy, Davide Napoletano, Paolo Nason, Tobias Neumann, L. J. Nevay, Oreste Nicrosini, J. Niehues, K. Niewczas, Thorsten Ohl, Giovanni Ossola, V. Pandey, A. Papadopoulou, Andreas Papaefstathiou, Gil Paz, Mathieu Pellen, Giovanni Pelliccioli, T. Peraro, Fluvio Piccinini, L. Pickering, J. Pires, Wieslaw Placzek, Simon Plätzer, Tilman Plehn, Stefano Pozzorini, Stefan Prestel, Christian Tobias Preuss, A. C. Price, Seth Quackenbush, Emanuele Re, Daniel Reichelt, Laura Reina, Christian Reuschle, Peter Richardson, M. Rocco, N. Rocco, M. Roda, A. Rodriguez Garcia, Stefan Roiser, Juan Rojo, Luca Rottoli, Gavin P. Salam, Marek Schönherr, S. Schuchmann, Steffen Schumann, Robin Schürmann, Ludovic Scyboz, Michael H. Seymour, Frank Siegert, Adrian Signer, Gurpreet Singh Chahal, Andrzej Siódmok, Torbjörn Sjöstrand, Peter Skands, Jennifer M. Smillie, J. T. Sobczyk, Dennis Soldin, D. E. Soper, Alba Soto-Ontoso, Gregory Soyez, Giovanni Stagnitto, J. Tena-Vidal, O. Tomalak, Francesco Tramontano, Sebastian Trojanowski, Z. Tu, Sandro Uccirati, T. Ullrich, Yannick Ulrich, Marius Utheim, A. Valassi, Andrii Verbytskyi, Rob Verheyen, M. Wagman, D. Walker, B. R. Webber, L. Weinstein, O. White, James Whitehead, Marius Wiesemann, C. Wilkinson, C. Williams, Ramon Winterhalder, C. Wret, K. Xie, T.-Z. Yang, E. Yazgan, Giulia Zanderighi, S. Zanoli, Korinna Zapp Scipost Physics, 2024 We provide an overview of the status of Monte-Carlo event generators for high-energy particle physics. Guided by the experimental needs and requirements, we highlight areas of active development, and opportunities for future improvements. Particular emphasis is given to physics models and algorithms that are employed across a variety of experiments. These common themes in event generator development lead to a more comprehensive understanding of physics at the highest energies and intensities, and allow models to be tested against a wealth of data that have been accumulated over the past decades. A cohesive approach to event generator development will allow these models to be further improved and systematic uncertainties to be reduced, directly contributing to future experimental success. Event generators are part of a much larger ecosystem of computational tools. They typically involve a number of unknown model parameters that must be tuned to experimental data, while maintaining the integrity of the underlying physics models. Making both these data, and the analyses with which they have been obtained accessible to future users is an essential aspect of open science and data preservation. It ensures the consistency of physics models across a variety of experiments.
A POWHEG generator for deep inelastic scattering Andrea Banfi, Silvia Ferrario Ravasio, Barbara Jäger, Alexander Karlberg, Felix Reichenbach, Giulia Zanderighi Journal of High Energy Physics, 2024 We present a new event generator for the simulation of both neutral- and charged-current deep inelastic scattering (DIS) at next-to-leading order in QCD matched to parton showers using the POWHEG method. Our implementation builds on the existing POWHEG BOX framework originally designed for hadron-hadron collisions, supplemented by considerable extensions to account for the genuinely different kinematics inherent to lepton-hadron collisions. In particular, we present new momentum mappings that conserve the special kinematics found in DIS, which we use to modify the POWHEG BOX implementation of the Frixione-Kunszt-Signer subtraction mechanism. We compare our predictions to fixed-order and resummed predictions, as well as to data from the HERA ep collider. Finally we study a few representative distributions for the upcoming Electron Ion Collider.
Precise predictions for boosted Higgs production Kathrin Becker, Fabrizio Caola, Andrea Massironi, Bernhard Mistlberger, Pier Francesco Monni, Xuan Chen, Stefano Frixione, Thomas Gehrmann, Nigel Glover, Keith Hamilton, Alexander Huss, Stephen Jones, Alexander Karlberg, Matthias Kerner, Kirill Kudashkin, Jonas M. Lindert, Gionata Luisoni, Michelangelo Mangano, Stefano Pozzorini, Emanuele Re, Gavin P. Salam, Eleni Vryonidou, Christopher Wever Scipost Physics Core, 2024
Precise predictions for same-sign W-boson scattering at the LHC Alessandro Ballestrero, Benedikt Biedermann, Simon Brass, Ansgar Denner, Stefan Dittmaier, Rikkert Frederix, Pietro Govoni, Michele Grossi, Barbara Jäger, Alexander Karlberg, Ezio Maina, Mathieu Pellen, Giovanni Pelliccioli, Simon Plätzer, Michael Rauch, Daniela Rebuzzi, Jürgen Reuter, Vincent Rothe, Christopher Schwan, Hua-Sheng Shao, Pascal Stienemeier, Giulia Zanderighi, Marco Zaro, Dieter Zeppenfeld European Physical Journal C, 2018
Precision studies of observables in pp→ W→ lνl and pp→ γ, Z→ l+l- processes at the LHC S. Alioli, A. B. Arbuzov, D. Yu. Bardin, L. Barzè, C. Bernaciak, S. G. Bondarenko, C. M. Carloni Calame, M. Chiesa, S. Dittmaier, G. Ferrera, D. de Florian, M. Grazzini, S. Höche, A. Huss, S. Jadach, L. V. Kalinovskaya, A. Karlberg, F. Krauss, Y. Li, H. Martinez, G. Montagna, A. Mück, P. Nason, O. Nicrosini, F. Petriello, F. Piccinini, W. Płaczek, S. Prestel, E. Re, A. A. Sapronov, M. Schönherr, C. Schwinn, A. Vicini, D. Wackeroth, Z. Was, G. Zanderighi European Physical Journal C, 2017
Electroweak Higgs boson pair production: Updated inclusive cross sections R Gröber, A Karlberg, M Pellen, G Sacchi, M Spira arXiv preprint arXiv:2603.02764 , 2026 2026
hoppet v2 release note A Karlberg, P Nason, G Salam, G Zanderighi, F Dreyer The European Physical Journal C 86 (2), 157 , 2026 2026 Citations: 6
Electroweak Higgs pair production:\\Updated inclusive cross sections R Groeber, M Spira, G Sacchi, A Karlberg, M Pellen 2026 Citations: 2
State-of-the-art electroweak Higgs boson pair production in association with two jets at the LHC in the Standard Model and beyond J Braun, P Bredt, G Heinrich, M Höfer, B Jäger, A Karlberg, S Reinhardt arXiv preprint arXiv:2511.02488 , 2025 2025
arXiv: HOPPET v2. 0.0 release note A Karlberg, P Nason, F Dreyer, G Zanderighi, G Salam 2025
HOPPET v2. 0.0 release note A Karlberg, P Nason, G Salam, G Zanderighi, F Dreyer arXiv e-prints, arXiv: 2510.09310 , 2025 2025 Citations: 6
Logarithmically-accurate and positive-definite NLO shower matching M van Beekveld, S Ferrario Ravasio, J Helliwell, A Karlberg, GP Salam, ... Journal of High Energy Physics 2025 (10), 1-58 , 2025 2025 Citations: 17
State-of-the-art electroweak Higgs-pair production in association with two jets at the LHC in the Standard Model and beyond J Braun, B Jäger, S Reinhardt, GM Heinrich, A Karlberg, M Höfer 2025 Citations: 2
An event generator for neutrino-induced deep inelastic scattering and applications to neutrino astronomy SF Ravasio, R Gauld, B Jäger, A Karlberg, G Zanderighi The European Physical Journal C 85 (8), 888 , 2025 2025 Citations: 18
Precision tools for the simulation of double-Higgs production via vector-boson fusion B Jäger, A Karlberg, S Reinhardt Journal of High Energy Physics 2025 (6), 1-21 , 2025 2025 Citations: 17
arXiv: Logarithmically-accurate and positive-definite NLO shower matching M van Beekveld, J Helliwell, A Soto-Ontoso, S Zanoli, L Scyboz, ... 2025
arXiv: Precision tools for the simulation of double-Higgs production via vector-boson fusion B Jäger, S Reinhardt, A Karlberg 2025
New standard for the logarithmic accuracy of parton showers M Van Beekveld, M Dasgupta, BK El-Menoufi, S Ferrario Ravasio, ... Physical Review Letters 134 (1), 011901 , 2025 2025 Citations: 46
Higgs production via vector-boson fusion at the LHC G Barone, J Chen, S Cooperstein, N Dolganov, S Ferrario Ravasio, ... SciPost physics community reports 13, 1-33 , 2025 2025 Citations: 2
Benchmark of deep-inelastic-scattering structure functions at O α s 3 V Bertone, A Karlberg The European Physical Journal C 84 (8), 774 , 2024 2024 Citations: 9
Codebase release r1. 0 for disorder A Karlberg SciPost Physics Codebases, 032 , 2024 2024
disorder: Deep inelastic scattering at high orders A Karlberg SciPost Physics Codebases, 032 , 2024 2024 Citations: 4
arXiv: An event generator for neutrino-induced Deep Inelastic Scattering and applications to neutrino astronomy S Ferrario Ravasio, B Jäger, G Zanderighi, A Karlberg, R Gauld 2024
Two-loop anomalous dimensions for small-R jet versus hadronic fragmentation functions M van Beekveld, M Dasgupta, BK El-Menoufi, J Helliwell, A Karlberg, ... Journal of High Energy Physics 2024 (7), 1-28 , 2024 2024 Citations: 11
Codebase release r0. 1 for PanScales M van Beekveld, M Dasgupta, BK El-Menoufi, S Ferrario Ravasio, ... SciPost Physics Codebases, 031 , 2024 2024
MOST CITED SCHOLAR PUBLICATIONS
CERN Yellow Reports: Monographs, Vol 2 (2017): Handbook of LHC Higgs cross sections: 4. Deciphering the nature of the Higgs sector D de Florian, C Grojean, F Maltoni, C Mariotti, A Nikitenko, M Pieri, ... CERN Yellow Reports: Monographs 2 , 2017 2017 Citations: 3272
Higgs physics at the HL-LHC and HE-LHC M Cepeda, S Gori, P Ilten, M Kado, F Riva, RA Khalek, A Aboubrahim, ... arXiv preprint arXiv:1902.00134 , 2019 2019 Citations: 1008
Fully differential vector-boson-fusion Higgs production at next-to-next-to-leading order M Cacciari, FA Dreyer, A Karlberg, GP Salam, G Zanderighi Physical review letters 115 (8), 082002 , 2015 2015 Citations: 486
Vector-boson fusion Higgs pair production at FA Dreyer, A Karlberg Physical Review D 98 (11), 114016 , 2018 2018 Citations: 316
Standard Model physics at the HL-LHC and HE-LHC P Azzi, S Farry, P Nason, A Tricoli, D Zeppenfeld, RA Khalek, J Alimena, ... arXiv preprint arXiv:1902.04070 , 2019 2019 Citations: 315
Vector-boson fusion Higgs production at three loops in QCD FA Dreyer, A Karlberg Physical Review Letters 117 (7), 072001 , 2016 2016 Citations: 266
Physics at a 100 TeV pp collider: Higgs and EW symmetry breaking studies R Contino, D Curtin, A Katz, ML Mangano, G Panico, MJ Ramsey-Musolf, ... arXiv preprint arXiv:1606.09408 , 2016 2016 Citations: 217
Precise predictions for same-sign W-boson scattering at the LHC A Ballestrero, B Biedermann, S Brass, A Denner, S Dittmaier, R Frederix, ... The European Physical Journal C 78 (8), 671 , 2018 2018 Citations: 194
Physics at a 100 TeV pp collider: Standard Model processes ML Mangano, G Zanderighi, JA Saavedra, S Alekhin, S Badger, ... arXiv preprint arXiv:1607.01831 , 2016 2016 Citations: 189
Event generators for high-energy physics experiments JM Campbell, M Diefenthaler, TJ Hobbs, S Höche, J Isaacson, F Kling, ... SciPost physics 16 (5), 130 , 2024 2024 Citations: 179
NNLOPS accurate Drell-Yan production A Karlberg, E Re, G Zanderighi Journal of High Energy Physics 2014 (9), 1-31 , 2014 2014 Citations: 166
Precision studies of observables in and processes at the LHC S Alioli, AB Arbuzov, DY Bardin, L Barzè, C Bernaciak, SG Bondarenko, ... The European Physical Journal C 77 (5), 280 , 2017 2017 Citations: 141
Fully differential vector-boson fusion Higgs pair production at next-to-next-to-leading order FA Dreyer, A Karlberg Physical Review D 99 (7), 074028 , 2019 2019 Citations: 112
Parton-shower effects in Higgs production via vector-boson fusion B Jäger, A Karlberg, S Plätzer, J Scheller, M Zaro The European Physical Journal C 80 (8), 756 , 2020 2020 Citations: 95
Spin correlations in final-state parton showers and jet observables A Karlberg, GP Salam, L Scyboz, R Verheyen The European Physical Journal C 81 (8), 681 , 2021 2021 Citations: 80
Les Houches 2017: physics at TeV colliders standard model working group report J Bendavid, F Caola, V Ciulli, R Harlander, G Heinrich, J Huston, ... arXiv preprint arXiv:1803.07977 , 2018 2018 Citations: 76
Parton showering with higher logarithmic accuracy for soft emissions S Ferrario Ravasio, K Hamilton, A Karlberg, GP Salam, L Scyboz, ... Physical Review Letters 131 (16), 161906 , 2023 2023 Citations: 72
Precise predictions for boosted Higgs production K Becker, F Caola, A Massironi, B Mistlberger, PF Monni, X Chen, ... SciPost Physics Core 7 (1), 001 , 2024 2024 Citations: 66
Soft spin correlations in final-state parton showers K Hamilton, A Karlberg, GP Salam, L Scyboz, R Verheyen Journal of High Energy Physics 2022 (3), 193 , 2022 2022 Citations: 61
Electroweak ZZjj production in the Standard Model and beyond in the POWHEG-BOX V2 B Jäger, A Karlberg, G Zanderighi Journal of High Energy Physics 2014 (3), 1-19 , 2014 2014 Citations: 61
