We present a systematic decomposition of QCD splitting functions into scalar dipole radiators and pure splitting remainders up to second order in the strong coupling. The individual components contain terms that are formally subleading in soft or collinear scaling parameters, but well understood and universal due to their origin in scalar QCD. The multipole radiator functions which we derive share essential features of the known double-soft and one-loop soft gluon currents, and are not based on kinematical approximations.

United States

John M. Campbell

Stefan Höche

Max Knobbe

Germany

Christian T. Preuss

CERN

Daniel Reichelt

QCD splitting functions beyond kinematical limits

We present state-of-the-art hadron-level predictions for the deep-inelastic scattering process at next-to-leading-order precision for several multiplicities, consistently merged in one sample. For the first time at this level of accuracy, we consider both neutral and charged current deep-inelastic scattering at the Electron-Ion Collider and present the first application of consistent next-to-leading-order merging to charged current deep-inelastic scattering in general. We critically examine inclusive predictions using multileg merging techniques, contrasting perturbative and nonperturbative uncertainties. Further, we study typical kinematic deep-inelastic scattering observables as well as jet measurements and 1-jettiness with realistic cuts implied by expected and past detector resolution. On the perturbative side, we see large corrections toward small virtualities and Bjorken-<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>x</mi></math>, which can be captured by higher-multiplicity matrix elements and the merging procedure. Nonperturbative effects, while negligible in most jet observables, can reach similar size as the perturbative uncertainties around the peak of the 1-jettiness distributions especially at low values of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>Q</mi><mn>2</mn></msup></math>.

Switzerland

Peter Meinzinger

United Kingdom

Federico Silvetti

Event generation at MEPS@NLO accuracy in neutral and charged current DIS at the EIC

The accurate identification of heavy-flavour jets — those which originate from bottom or charm quarks — is crucial for precision studies of the Standard Model and searches for new physics. However, assigning flavour to jets presents significant challenges, primarily due to issues with infrared and collinear (IRC) safety. This paper aims to address these challenges by evaluating recently-proposed jet algorithms designed to be IRC-safe and applicable in high-precision measurements. We compare these algorithms across benchmark heavy-flavour production processes and kinematic regimes that are relevant for LHC phenomenology. Exploiting both fixed-order calculations in QCD as well as parton shower simulations, we analyse the infrared sensitivity of these new algorithms at different stages of the event evolution and compare to flavour labelling strategies currently adopted by LHC collaborations. The results highlight that, while all algorithms lead to more robust flavour assignments compared to current techniques, they vary in performance depending on the observable and energy regime. The study lays groundwork for robust, flavour-aware jet analyses in current and future collider experiments to maximise the physics potential of experimental data by reducing discrepancies between theoretical and experimental methods.

Arnd Behring

Simone Caletti

Italy

Francesco Giuli

Radosław Grabarczyk

Andreas Hinzmann

Alexander Huss

Joey Huston

Ezra Lesser

Simone Marzani

Davide Napoletano

Poland

Rene Poncelet

Alberto Rescia

Gavin Salam

Australia

Ludovic Scyboz

Federico Sforza

Andrzej Siódmok

Giovanni Stagnitto

James Whitehead

Ruide Xu

Flavoured jet algorithms: a comparative study

We introduce the alaric parton shower for simulating quantum chromodynamics (QCD) radiation at hadron colliders and present numerical results from an implementation in the event generator sherpa. alaric provides a consistent framework to quantify certain systematic uncertainties which cannot be eliminated by comparing the parton shower with analytic resummation. In particular, it allows us to study recoil effects away from the soft and collinear limits without the need to change the evolution variable or the splitting functions. We assess the performance of alaric in Drell-Yan lepton pair and QCD jet production, and present the first multijet merging for the new algorithm.

Frank Krauss

alaric parton shower for hadron colliders

Sherpa is a general-purpose Monte Carlo event generator for the simulation of particle collisions in high-energy collider experiments. We summarise new developments, essential features, and ongoing improvements within the Sherpa 3 release series. Physics improvements include higher-order electroweak corrections, simulations of photoproduction and hard diffraction at NLO QCD, heavy-flavour matching in NLO multijet merging, spin-polarised cross section calculations, and a new model of colour reconnections. In addition, the modelling of hadronisation, the underlying event and QED effects in both production and decay has been improved, and the overall event generation efficiency has been enhanced.

Enrico Bothmann

Lois Flower

Christian Gütschow

Mareen Hoppe

Joshua Isaacson

Alan Price

Marek Schönherr

Steffen Schumann

Frank Siegert

Event generation with Sherpa 3

We investigate the impact of electroweak corrections and effective field theory operators on <math><msup><mi>W</mi><mo>+</mo></msup><msup><mi>W</mi><mo>−</mo></msup></math> production at the Large Hadron Collider (LHC). Utilizing the Standard Model effective-field theory (SMEFT) framework, we extend the Standard Model by incorporating higher-dimensional operators to encapsulate potential new physics effects. These operators allow for a model-independent approach to data interpretation, essential for probing beyond the Standard Model physics. We generate pseudodata at the next-to-leading order in quantum chromodynamics and include approximate electroweak corrections. Our analysis focuses on the interplay between these corrections and SMEFT operators at leading order. The inclusion of electroweak corrections is crucial as they can counteract the effects predicted by SMEFT operators, necessitating precise theoretical and experimental handling. By examining <math><mi>p</mi><mi>p</mi><mo>→</mo><msup><mi>W</mi><mo>+</mo></msup><msup><mi>W</mi><mo>−</mo></msup></math> production, a process sensitive to the electroweak symmetry-breaking mechanism, we demonstrate the importance of these corrections in isolating and interpreting new physics signatures. Our results highlight the significant role of electroweak corrections in enhancing the interpretative power of LHC data and in obtaining reliable constraints on new physics interactions.

India

Shankha Banerjee

Michael Spannowsky

Electroweak corrections and EFT operators in <math><mrow><msup><mrow><mi>W</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>W</mi></mrow><mrow><mo>−</mo></mrow></msup></mrow></math> production at the LHC

We study jet angularities for dijet production at the Relativistic Heavy Ion Collider (RHIC) in proton-proton (pp) and nucleus-nucleus (AA) collisions at 200 GeV nucleon-nucleon center-of-mass collision energy. In particular, we provide NLL resummed predictions for angularity observables of groomed and ungroomed jets produced in pp collisions matched to next-to-leading order QCD calculations resulting in NLO + NLL ′  accuracy. Our parton-level predictions are corrected for non-perturbative effects, such as hadronization and underlying event, using parton-to-hadron level transfer matrices obtained with the Sherpa event generator. Furthermore, we use the Q-Pythia and Jewel generators to estimate the impact of the interaction between quarks and gluons produced by the parton shower with the dense medium formed in heavy-ion collisions on the considered jet angularities.

Yang-Ting Chien

Oleh Fedkevych

Jet angularities in dijet production in proton-proton and heavy-ion collisions at RHIC

We present resummed predictions at next-to-leading logarithmic accuracy matched to the exact next-to-leading order results for a set of classical event-shape observables in hadronic Higgs decays, i.e., for the channels H → gg and H → <math> <mi>b</mi> <mover> <mi>b</mi> <mo>¯</mo> </mover> </math> $$ b\overline{b} $$ . We furthermore consider soft-drop grooming of the hadronic final states and derive corresponding NLO+NLL′ predictions for the groomed thrust observable. Differences in the QCD radiation pattern of gluon- and quark-initiated final states are imprinted in the event-shape distributions, offering separation power for the two decay channels. In particular, we show that ungroomed event shapes in H → gg decays develop a considerably harder spectrum than in H → <math> <mi>b</mi> <mover> <mi>b</mi> <mo>¯</mo> </mover> </math> $$ b\overline{b} $$ decays. We highlight that soft-drop grooming can substantially alter this behaviour, unless rather inclusive grooming parameters are chosen.

Aude Gehrmann-De Ridder

Christian Preuss

NLO+NLL′ accurate predictions for three-jet event shapes in hadronic Higgs decays

We present a novel strategy for the simultaneous measurement of Higgs-boson branching ratios into gluons and light quarks at a future lepton collider operating in the Higgs-factory mode. Our method is based on template fits to global event-shape observables, and in particular fractional energy correlations, thereby exploiting differences in the QCD radiation patterns of quarks and gluons. In a constrained fit of the deviations of the light-flavour hadronic Higgs-boson branching ratios from their Standard Model expectations, based on an integrated luminosity of $$5\,\text {ab}^{-1}$$ <math> <mrow> <mn>5</mn> <mspace width="0.166667em"></mspace> <msup> <mtext>ab</mtext> <mrow> <mo>-</mo> <mn>1</mn> </mrow> </msup> </mrow> </math> , we obtain $$68\%$$ <math> <mrow> <mn>68</mn> <mo>%</mo> </mrow> </math> confidence level limits of $$\mu _{gg}=1 \pm 0.05$$ <math> <mrow> <msub> <mi>μ</mi> <mrow> <mi>gg</mi> </mrow> </msub> <mo>=</mo> <mn>1</mn> <mo>±</mo> <mn>0.05</mn> </mrow> </math> and $$\mu _{q\bar{q}}&lt;21$$ <math> <mrow> <msub> <mi>μ</mi> <mrow> <mi>q</mi> <mover> <mrow> <mi>q</mi> </mrow> <mrow> <mo>¯</mo> </mrow> </mover> </mrow> </msub> <mo>&lt;</mo> <mn>21</mn> </mrow> </math> .

Measuring hadronic Higgs boson branching ratios at future lepton colliders

We present a simple parton-shower model that replaces the explicit angular ordering of the coherent branching formalism with a differentially accurate simulation of soft-gluon radiation by means of a non-trivial dependence of the splitting functions on azimuthal angles. We introduce a global kinematics mapping and provide an analytic proof that it satisfies the criteria for next-to leading logarithmic accuracy. In the new algorithm, initial and final state evolution are treated on the same footing. We provide an implementation for final-state evolution in the numerical code A and present a first comparison to experimental data.

Florian Herren

A new approach to color-coherent parton evolution