(N)NLO+NLL’ accurate predictions for plain and groomed 1-jettiness in neutral current DIS

The possibility to reanalyse data taken by the HERA experiments offers the chance to study modern QCD jet and event-shape observables in deep-inelastic scattering. To address this, we compute resummed and matched predictions for the 1-jettiness distribution in neutral current DIS with and without grooming the hadronic final state using the soft-drop technique. Our theoretical predictions also account for non-perturbative corrections from hadronisation through parton-to-hadron level transfer matrices extracted from dedicated Monte Carlo simulations with Sherpa. To estimate parameter uncertainties in particular for the beam-fragmentation modelling we derive a family of replica tunes to data from the HERA experiments. While NNLO QCD normalisation corrections to the NLO+NLL’ prediction are numerically small, hadronisation corrections turn out to be quite sizeable. However, soft-drop grooming significantly reduces the impact of non-perturbative contributions. We supplement our study with hadron-level predictions from Sherpa based on the matching of NLO QCD matrix elements with the parton shower. Good agreement between the predictions from the two calculational methods is observed

Measuring Hadronic Higgs Boson Branching Ratios at Future Lepton Colliders

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 $5\,\text{ab}^{-1}$, we obtain $68\%$ confidence level limits of $\mu_{gg}=1 \pm 0.08$ and $\mu_{q\bar{q}}<2.3$.Comment: 12 pages, 6 figures, 2 table

Measuring hadronic Higgs boson branching ratios at future lepton colliders

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 5ab-1, we obtain 68% confidence level limits of μgg=1±0.05 and μqq¯<21

A Portable Parton-Level Event Generator for the High-Luminosity LHC

Parton-level event generators are one of the most computationally demanding parts of the simulation chain for the Large Hadron Collider. The rapid deployment of computing hardware different from the traditional CPU+RAM model in data centers around the world mandates a change in event generator design. These changes are required in order to provide economically and ecologically sustainable simulations for the high-luminosity era of the LHC. We present the first complete leading-order parton-level event generation framework capable of utilizing most modern hardware. Furthermore, we discuss its performance in the standard candle processes of vector boson and top-quark pair production with up to five additional jets.Comment: Submission to SciPost, 23 pages, 7 figures, 2 table

Efficient precision simulation of processes with many-jet final states at the LHC

We present a scalable technique for the simulation of collider events with multi-jet final states, based on an improved parton-level event file format. The method is implemented for both leading- and next-to-leading order QCD calculations. We perform a comprehensive analysis of the I/O performance and validate our new framework using Higgs-boson plus multi-jet production with up to seven jets. We make the resulting code base available for public use.Comment: 14 pages, 7 figures, 2 table

Efficient phase-space generation for hadron collider event simulation

We present a simple yet efficient algorithm for phase-space integration at hadron colliders. Individual mappings consist of a single t-channel combined with any number of s-channel decays, and are constructed using diagrammatic information. The factorial growth in the number of channels is tamed by providing an option to limit the number of s-channel topologies. We provide a publicly available, parallelized code in C++ and test its performance in typical LHC scenarios.Comment: 11 pages, 3 figure

Accelerating LHC event generation with simplified pilot runs and fast PDFs

Poor computing efficiency of precision event generators for LHC physics has become a bottleneck for Monte-Carlo event simulation campaigns. We provide solutions to this problem by focusing on two major components of general-purpose event generators: The PDF evaluator and the matrix-element generator. For a typical production setup in the ATLAS experiment, we show that the two can consume about 80% of the total runtime. Using NLO simulations of pp→ℓ+ℓ-+jets and pp→tt¯+jets as an example, we demonstrate that the computing footprint of Lhapdf and Sherpa can be reduced by factors of order 10, while maintaining the formal accuracy of the event sample. The improved codes are made publicly available

(N)NLO+NLL’ accurate predictions for plain and groomed 1-jettiness in neutral current DIS

Abstract The possibility to reanalyse data taken by the HERA experiments offers the chance to study modern QCD jet and event-shape observables in deep-inelastic scattering. To address this, we compute resummed and matched predictions for the 1-jettiness distribution in neutral current DIS with and without grooming the hadronic final state using the soft-drop technique. Our theoretical predictions also account for non-perturbative corrections from hadronisation through parton-to-hadron level transfer matrices extracted from dedicated Monte Carlo simulations with Sherpa. To estimate parameter uncertainties in particular for the beam-fragmentation modelling we derive a family of replica tunes to data from the HERA experiments. While NNLO QCD normalisation corrections to the NLO+NLL’ prediction are numerically small, hadronisation corrections turn out to be quite sizeable. However, soft-drop grooming significantly reduces the impact of non-perturbative contributions. We supplement our study with hadron-level predictions from Sherpa based on the matching of NLO QCD matrix elements with the parton shower. Good agreement between the predictions from the two calculational methods is observed