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Parton Showers and Resummation 2025

14–18 Jul 2025
CERN
Europe/Zurich timezone

TH workshop secretariat

Contribution List

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  1. 30. Welcome
    Alba Soto Ontoso (Universidad de Granada (ES)), Alexander Karlberg (CERN), Daniel Reichelt, Luca Buonocore (CERN), Pier Francesco Monni (CERN)
    14/07/2025, 13:15
  2. 26. Current limitations of event generators in experimental analyses at the LHC
    Jennifer Roloff (Brown University (US))
    14/07/2025, 13:25
  3. 37. Conceptual and technical challenges in the matching of parton showers to higher-order calculations
    Peter Skands (Monash University (AU))
    14/07/2025, 14:20
  4. 11. LHC phenomenology with KrkNLO matching
    Andrzej Konrad Siodmok (Jagiellonian University (PL))
    14/07/2025, 15:00

    The systematic combination of perturbative QCD with parton-shower resummation is achieved at NLO by a small, but growing, number of 'NLO matching' methods.

    Among them, the KrkNLO method is unique in exploiting a modification of the PDF factorisation scheme, from the conventional $\overline{\mathrm{MS}}$ scheme, to a scheme (the 'Krk' scheme) in which the NLO corrections can be applied as a...

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  5. 39. Current status of NNLOPS simulations at LHC
    Luca Rottoli (Universita & INFN, Milano-Bicocca (IT))
    14/07/2025, 16:00
  6. 38. Logarithmically-accurate and positive-definite NLO shower matching with ESME
    Alexander Karlberg (CERN)
    14/07/2025, 16:40
  7. 6. NNLO matching in VINCIA
    Basem El-Menoufi
    14/07/2025, 17:20

    Fixed-order matching of Monte Carlo showers remains a critical ingredient to push forward the precision frontier of collider phenomenology. Beyond the conceptually simple leading-order matching, the past two decades have seen multiple techniques to achieve next-to-leading order (NLO) matching which have further been fully automated and made available in public codes. This pushed the precision...

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  8. 15. Final-state NLO matching in Alaric
    Peter Meinzinger (Zürich University)
    14/07/2025, 17:50

    In this talk, we present steps towards automated matching of the Alaric parton shower to NLO QCD matrix elements for lepton collisions in Sherpa. We validate our implementation against jet production in $e^+e^- \to$ jets for up to five jets. We show numerical tests of the subtraction in the infrared limit, benchmarking against the Catani-Seymour subtraction. We then present first hadron-level...

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  9. 32. The Alaric project
    Stefan Hoeche (Fermilab)
    15/07/2025, 09:00
  10. 31. PanScales efforts towards NNLL showers
    Gregory Soyez (IPhT, CEA Saclay)
    15/07/2025, 09:40
  11. 52. Status of NLL-Accurate Parton Showers in Herwig
    Siddharth Sule (The University of Manchester (GB))
    15/07/2025, 10:20
  12. 48. Recent progress in subleading-colour effects and amplitude-level evolution
    Simon Platzer (University of Graz (AT))
    15/07/2025, 11:20
  13. 43. Hadronization models with NLL-accurate showers in Herwig
    Andre Hoang (Austrian Academy of Sciences (AT))
    15/07/2025, 12:00
  14. 44. Anomalous scaling of linear power corrections
    Silvia Zanoli (University of Oxford)
    15/07/2025, 14:00
  15. 47. Merging non-perturbative corrections in the two- and three-jet region
    Andrea Banfi (University of Sussex)
    15/07/2025, 14:40
  16. 24. A Precise Determination of $\alpha_s$ from Heavy Jet Mass
    Arindam Bhattacharya
    15/07/2025, 15:10

    A global fit for $\alpha_s(m_Z)$ is performed on available $e^+e^-$ data for the heavy jet mass distribution. The state-of-the-art theory prediction includes $\mathcal{O}(\alpha_s^3)$ fixed-order results, N$^3$LL$^\prime$ dijet resummation, N$^2$LL Sudakov shoulder resummation, and a first-principles treatment of power corrections in the dijet region. Theoretical correlations are incorporated...

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  17. 23. Decomposition of QCD splitting functions into scalar radiators and pure remainders
    Max Knobbe (University of Göttingen)
    15/07/2025, 16:00

    In this talk, I will present a new decomposition of QCD splitting functions, carried out systematically up to second order in the strong coupling. The core idea is to separate the splitting functions into two components: scalar dipole radiator functions and pure remainders. Unlike conventional approaches, our construction does not rely on any soft or collinear approximations. The splitting...

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  18. 9. Four-top production at the LHC: improving predictions with invariant-mass threshold resummation.
    Tommaso Saracco (Nikhef)
    15/07/2025, 16:00

    We present new results for the invariant-mass distribution and total cross section for four-top production, incorporating the resummation of soft-gluon corrections at improved next-to-leading logarithmic accuracy, including non-logarithmic $\mathcal{O}(\alpha_s)$ terms (NLL’ accuracy). After discussing the challenges of invariant-mass threshold resummation in processes with six coloured legs,...

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  19. 17. A novel algorithm for spin correlations in parton evolution
    Diana Mareen Hoppe (Technische Universitaet Dresden (DE))
    15/07/2025, 16:30

    Spin correlations between QCD emissions have so far been neglected in most of the parton shower algorithms commonly used for LHC predictions. However, their inclusion is crucial to achieve NLL accuracy or to include NLO contributions in these algorithms.
    In this talk, we present a new algorithm for incorporating spin correlations into parton shower algorithms. Instead of using spin density...

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  20. 4. Factorization and Resummation in Threshold PDFs
    Marvin Schnubel (BNL)
    15/07/2025, 16:30

    We study factorization at next-to-leading power (NLP) in deep inelastic scattering (DIS) in the endpoint region $x\to1$ within the framework of soft-collinear effective theory (SCET). The full QCD process is matched onto two SCET currents, whose matrix elements factorize into individual component functions. By employing endpoint reshuffling theorems that relate these component functions at...

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  21. 54. Parton shower recoil with jets
    Jack Helliwell (Monash University (AU))
    15/07/2025, 17:00
  22. 8. Threshold resummation for VV pair production to NNLO+NNLL at the LHC (Zoom)
    Vaibhav Pandey (Indian Institute of Technology Guwahati)
    15/07/2025, 17:00

    We perform the threshold resummation for massive vector boson pair production processes ($ZZ$ and $W^{+}W^{-}$) in hadron collisions to Next to Next Leading Log accuracy. The resummed cross-sections are then matched with NNLO fixed order results, which are obtained using the MATRIX code. We present our results for the invariant mass distribution to NNLO+NNLL accuracy in QCD for the current LHC...

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  23. 12. Large-x Resummation for Transverse Momentum Distributions
    Óscar del Río García (Complutense University of Madrid)
    15/07/2025, 17:30

    In this talk, I discuss the resummation of leading logarithmic contributions to the collinear matching coefficients of Transverse Momentum Dependent distributions (TMDs) in the large-$x$ regime. Resummation is performed directly at the level of TMDs, preserving their process-independence and, for the first time, covering distributions that match onto twist‑three collinear Parton Distribution...

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  24. 3. Towards two-loop EW corrections at NLL in OpenLoops
    Lorenzo Mai (University of Genova)
    15/07/2025, 17:30

    At energies above the Electroweak (EW) scale, higher-order EW corrections exhibit a logarithmic enhancement which is driven by the ratio of the typical scattering energy to the gauge-boson mass. At next-to-leading order (NLO) these corrections lead to factors amounting to several tens of percent in tails of kinematic distributions of crucial LHC processes, and still contribute a few percent at...

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  25. 5. Small-x Resummed Gluon Densities from HELL and Applications with JETHAD (Zoom)
    Dr Francesco Giovanni Celiberto (UAH Madrid)
    15/07/2025, 18:00

    We review the state of the art in applying the small-x resummation to parton distribution functions in the proton, with particular emphasis on the gluon content. In the first part, we briefly discuss small-x resummed 1D collinear distributions, highlighting their connections with the 3D transverse-momentum dependent counterparts at both small and moderate x, including the effects of...

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  26. 34. Recent developments in jet substructure calculations
    Simone Marzani (Università di Genova and INFN Sezione di Genova)
    16/07/2025, 09:00
  27. 35. Recent theoretical advancements in the description of energy correlations
    Huaxing Zhu (ZJU - Zhejiang University (CN))
    16/07/2025, 09:40
  28. 58. From Correlation Functions to Collider Observables: Unlocking Precision for Charge Dynamics in QCD
    Gherardo Vita
    16/07/2025, 11:20
  29. 42. Non-perturbative corrections to the projected N-point energy correlators
    Aditya Pathak (DESY)
    16/07/2025, 12:00
  30. 36. TH colloquium: The Strong Interaction at 50 Years: less Puzzling, more Rich, and still Mysterious
    Iain Stewart
    16/07/2025, 14:00

    https://indico.cern.ch/event/1513473/

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  31. 46. Thrust distribution in electron-positron annihilation at full NNNLL+NNLO (and beyond) in QCD
    Giancarlo Ferrera (Università degli Studi e INFN Milano (IT))
    16/07/2025, 15:45
  32. 22. On Determining $\alpha_s(m_Z)$ from Dijets in $e^+e^-$ Thrust
    Miguel Benitez (University of Salamanca)
    16/07/2025, 16:25

    We update a previous N$^3$LL$^\prime$+${\cal O}(\alpha_s^3)$ determination of the strong coupling from a global fit to thrust data. Detailed discussions are provided concerning the stability of the results under variations of the fit range and the importance of summing up higher-order logarithmic terms for convergence and stability. We also demonstrate that a number of additional effects...

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  33. 45. Non-perturbative power corrections to $e^+e^-$ event shapes in the three-jet region and strong coupling fits
    Paolo Nason
    16/07/2025, 17:05
  34. 40. High-energy limit of QCD
    Einan Gardi
    17/07/2025, 09:00
  35. 41. All Orders Regge Factorization for Diffraction
    Iain Stewart
    17/07/2025, 09:40
  36. 7. Vector boson+dijets at large mjj
    Jeppe Andersen (IPPP, University of Durham)
    17/07/2025, 10:20

    We present the first calculation of high-energy corrections to the
    process of photon+dijet production. The high-energy corrections stabilise
    the fixed-order perturbative behaviour and lead to a significant
    improvement in the description of data.

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  37. 59. Jet veto in $Q\bar{Q}X$ production at the LHC
    Luca Buonocore (CERN)
    17/07/2025, 11:20
  38. 20. Super-leading logarithms from effective field theory
    Thomas Georg Becher (Universitaet Bern (CH))
    17/07/2025, 12:00

    Factorization theorems for non-global observables at hadron colliders can be used to resum super-leading logarithms (SLLs) and we present a phenomenological analysis of their numerical impact in pp -> 2 jets.

    SLLs are closely related to collinear factorization breaking and are driven by a double-logarithmic evolution equation in an effective field theory. The compatibility of this...

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  39. 2. Differential threshold resummation for hadronic and SIDIS processes
    Stefano Forte (Università degli Studi e INFN Milano (IT))
    17/07/2025, 14:00

    Using renormalization group arguments in dQCD, I derive an analytic resummation formula for the threshold resummation of differential distributions with fixed longitudinal partonic kinematics. By matching to existing fixed-order NNLO computations I obtain NLL resummation for the Drell-Yan rapidity distribution with fixed partonic rapidity and for semi-inclusive deep-inelastic scattering. For...

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  40. 61. NNLO predictions with nonlocal subtractions and fiducial power corrections
    Alessandro Broggio
    17/07/2025, 14:30
  41. 53. Towards a Quantum Information Theory of Hadronization
    Johannes Michel (Nikhef/University of Amsterdam)
    17/07/2025, 14:30
  42. 14. Renomalon analysis of SCET-II observables in the large-$\beta_0$ approximation
    Kevin Brune
    17/07/2025, 15:00

    We present a derivation of nonperturbative corrections to SCET-II-type observables in the large-$\beta_0$ approximation based on the bubble-sum approximation within the SCET framework. We demonstrate how to obtain the leading-power nonperturbative corrections using the collinear anomaly approach and further discuss their impact on the corresponding partonic cross sections.

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  43. 10. The Lund b-jet plane
    Andrea Ghira (Università degli studi di Genova)
    17/07/2025, 15:00

    In this talk, I will present our research on the substructure of jets containing heavy flavour. Our main goal is to better understand these jets from a theoretical perspective, using resummed perturbative techniques that are specially designed for jets coming from heavy quarks. In particular, we provide analytical predictions for several key jet substructure observables, including jet...

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  44. 56. Exponentiation of next-to-soft gluon and soft quark emissions from the replica trick
    Leonardo Vernazza (INFN, Torino)
    17/07/2025, 16:15
  45. 19. Super-leading logarithms and PDF factorization
    Dominik Schwienbacher
    17/07/2025, 16:15

    I analyze the low-energy dynamics of gap-between-jets cross sections at
    hadron colliders, for which phase factors in the hard amplitudes spoil
    collinear cancellations and lead to double (`super-leading') logarithmic
    behavior. Based on a method-of-regions analysis, I identify three-loop
    contributions from perturbative active-active Glauber-gluon exchanges with the correct structure to...

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  46. 55. NNLO soft function for 0-jettiness in tt production
    Sebastian Edelmann
    17/07/2025, 16:45
  47. 25. The perturbative structure of jet vetoes in azimuthal gaps
    Alexander Fraley (University of Manchester)
    17/07/2025, 16:45

    The distribution of transverse energy flow into an azimuthal strip presents novel theoretical features and accompanying challenges in its all-order description. Its resummation structure depends non-trivially on the axis definition, with the standard thrust axis breaking naive double-logarithmic exponentiation. Moreover it receives non-global logarithmic (NGL) enhancements that start with...

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  48. 57. SLLs in ttbar production
    UPALAPARNA BANERJEE (JGU Mainz)
    17/07/2025, 17:15
  49. 18. Three-loop jet function for boosted heavy quarks
    Alberto Martín Clavero
    17/07/2025, 17:15

    Previous studies have shown that certain observables at massless $e^+e^−$ colliders producing primary top quarks can be used to measure the top quark mass with an uncertainty smaller than $\Lambda_{\rm QCD}$. The maximal sensitivity to the top mass is attained in the peak of the distribution, where Effective Field Theories (EFTs) enable the factorization of the differential cross section...

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  50. 21. Partial N3LL + NNLO Resummed Predictions for the Drell-Yan Process in Rapidity Dependent Jet Veto Observables
    Thomas Clark
    17/07/2025, 17:45

    Jet vetoes are important tools that can be used to separate hard processes. A commonly used variable in which jets are identified and vetoed is the transverse momentum of a jet. It can also be useful to vary the tightness of such cuts depending on the rapidity of a jet depending on the focus on central or forward jets. This naturally leads to a class of such variables related to the leading...

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  51. 60. Soft anomalous dimensions with massive legs
    Zehao Zhu (University of Edinburg)
    17/07/2025, 17:45
  52. 28. Overview of jet physics in heavy-ion collisions
    Joao Lourenco Henriques Barata
    18/07/2025, 09:00
  53. 27. Theoretical understanding of QCD cascades in heavy-ion collisions
    Guilherme Milhano (LIP-Lisbon & CERN TH)
    18/07/2025, 09:40
  54. 13. KNO scaling in quark and gluon jets at the LHC
    Lin CHEN (Instituto Galego de Fisica de Altas Enerxias - IGFAE)
    18/07/2025, 10:20

    The Koba-Nielsen-Olesen (KNO) scaling of hadron multiplicity distributions, empirically confirmed to hold approximately in $e^+e^-$ collisions and Deep Inelastic Scattering, has been observed to be violated in hadron-hadron collisions. In this work, we show that the universality of KNO scaling can be extended to hadron-hadron collisions when restricted to QCD jets. We present a comprehensive...

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  55. 29. Recent developments in the calculation of higher-order matrix-element in heavy-ion collisions
    Peter Arnold (University of Virginia (US))
    18/07/2025, 11:20
  56. 51. Farewell
    Alba Soto Ontoso (Universidad de Granada (ES)), Alexander Karlberg (CERN), Daniel Reichelt, Luca Buonocore (CERN), Pier Francesco Monni (CERN)
    18/07/2025, 12:00