arXiv subjects

Marius Wiesemann

Publications and source records attributed to Marius Wiesemann.

At least 19 recordsLinked to original sources

arXiv2026

The production of bottom-flavoured jets at the LHC through bottom-quark pair production at NNLO+PS

We consider the dominant production mechanism of bottom-flavoured jets at the LHC, which proceeds through bottom-quark pair production. We compute next-to-next-to- leading-order (NNLO) QCD corrections retaining full bottom-quark mass effects and match them with a parton shower (NNLO+PS). Our predictions provide a realistic description of events with one and two bottom-flavoured jets at both the partonic and hadronic level. We compare different jet-flavour definitions and confirm that the dominant numerical differences between the jet algorithms result from the treatment of jets that contain two bottom quarks originating from $g\to b\bar b$ splittings. We compare our predictions, using the experimental bottom-flavour tagging prescription, with measurements by ATLAS, CMS, and LHCb at 7 and 13 TeV, finding good agreement for the distributions presented by ATLAS and CMS and a good description of the shapes of the LHCb data. We also discuss the impact of various physics effects on the considered distributions: power corrections in the bottom-quark mass, the implications of symmetric/asymmetric jet-selection cuts, as well as contributions from multi-parton interactions.

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arXiv2026

Next-to-next-to-leading order event generation for $t\bar{t}H$ production with approximate two-loop amplitude

We study Higgs-boson production in association with a top-quark pair ($t\bar{t}H$) at hadron colliders and present the first matching of next-to-next-to-leading order (NNLO) QCD corrections to parton showers using the MiNNLOPS method. For the two-loop amplitude, we employ two established approximations, based on the soft Higgs-boson and high-energy limits, respectively. For the first time, we also construct the latter in full colour and propose a pointwise combination of the two approximations across phase space. By assigning a conservative uncertainty estimate, which remains well below the perturbative uncertainties, we ensure robust and reliable differential predictions, explicitly validated at the one-loop level. Apart from the two-loop amplitude, all remaining ingredients of the MiNNLOPS calculation are included exactly. After thorough validation, we present a series of phenomenological results illustrating the impact of NNLO corrections and parton-shower effects. We consider fiducial predictions for the Higgs-boson decay into photons and include off-shell top-quark decays with tree-level spin correlations in both the dilepton and semileptonic channels. Our $t\bar{t}H$ MiNNLOPS generator is publicly available within the POWHEG framework.

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arXiv2026

Matrix element method at NLO: A fine proof of concept in POWHEG

The matrix element method (MEM) provides a fully probabilistic approach to confront experimental events with theory, retaining all correlations in the scattering matrix element. While leading-order MEM is widely used and automated, extending it to next-to-leading order (NLO) in QCD is challenging due to infrared divergences, negative weights, extra final-state partons, and multi-dimensional phase-space integration. We demonstrate that the POWHEG method offers a practical path to MEM at NLO accuracy. By projecting real-emission events onto Born kinematics via the mappings inherited from the $\tilde{B} (Φ)$ function, our method consistently includes the hardest QCD radiation while preserving the NLO-accurate normalization. As a proof of concept, we apply it to fully leptonic $W^+ W^-$ production in the Standard Model (SM) effective field theory, focusing on a CP-even dimension-six triple-gauge-boson operator. Our NLO MEM implementation acts as a near-optimal classifier, exploiting spin- and polarization-dependent correlations among the final-state leptons to efficiently distinguish beyond-the-SM (BSM) from SM events. This demonstrates the potential of MEM at NLO for precision studies of electroweak processes and subtle BSM effects.

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arXiv2026

NNLO+PS Higgs-pair production in MiNNLOPS

We consider Higgs-boson pair production in gluon fusion at hadron colliders and match next-to-next-to-leading-order (NNLO) QCD corrections to parton showers within the MiNNLO$_{PS}$ framework. Since the full top-quark mass dependence at this order is not available, finite top-quark mass effects are incorporated through approximations based on the exact NLO QCD result, using the available two-loop amplitude in the full theory. Specifically, the Born, single-virtual, single-real and double-real contributions are included exactly, while the real--virtual and double-virtual corrections are approximated. We consider different approximations for the latter to assess the associated uncertainties. We validate our predictions against fixed-order NNLO QCD results and compare with existing NNLO calculations matched to parton shower from GENEVA, where in some cases we find noticeable differences. Finally, we present phenomenological results for different Higgs-decay channels and variations of the trilinear Higgs coupling. Our MiNNLO$_{PS}$ generator for Higgs-boson pair production is available within the POWHEG-BOX-RES framework.

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arXiv2026

Modelling $b\bar b H$ production for the LHC at 13.6 TeV

We present new state-of-the-art predictions for Standard Model Higgs boson production in association with a bottom-quark pair ($b\bar bH$). Updated cross sections are computed in accordance with the recommendations of the LHC Higgs Working Group, including the use of the PDF4LHC21 set of parton distribution functions, with a center-of-mass energy of 13.6 TeV. For the total inclusive cross section, we provide matched predictions of the massless five-flavour scheme and the massive four-flavour scheme at the fixed-order level. We further present recently obtained simulations matched to parton showers in both flavour schemes within the Standard Model, and also discuss them in the context of potential Beyond-the-Standard-Model scenarios. In the massless scheme, we compare different next-to-next-to-leading order predictions matched to parton showers obtained through the MiNNLOPS and GENEVA generators. In addition, the role of four-flavour scheme predictions is studied as a background to $HH$ searches, considering both the top-quark and bottom-quark Yukawa contributions to $b\bar bH$ production. Finally, we analyse the sensitivity of the Higgs transverse momentum spectrum to light-quark Yukawa couplings in the diphoton decay channel based on MiNNLOPS simulations.

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arXiv2025

Higgs boson production in association with massive bottom quarks at NNLO+PS

We study the production of a Higgs boson in association with a bottom-quark pair ($b \bar b H$) at hadron colliders. Our calculation is performed in the four-flavour scheme with massive bottom quarks. This work presents the first computation of next-to-next-to-leading-order (NNLO) QCD corrections to this process, and we combine them with all-order radiative corrections from a parton shower simulation (NNLO+PS). The calculation is exact, except for the two-loop amplitude, which is evaluated in the small quark mass expansion, which is an excellent approximation for bottom quarks at LHC energies. For the NNLO+PS matching, we employ the MiNNLO$_{\rm PS}$ method for heavy-quark plus colour-singlet production within the POWHEG framework. We present an extensive phenomenological analysis both at the inclusive level and considering bottom jets using flavour-tagging algorithms. By comparing four-flavour and five-flavour scheme predictions at NNLO+PS, we find that the NNLO corrections in the four-flavour scheme resolve the long-standing tension between the two schemes. Finally, we show that our NNLO+PS predictions also have important implications on modelling the $b\bar b H$ background in Higgs-pair measurements.

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arXiv2024

Higgs-boson production in the full theory at NNLO+PS

We consider the production of a Standard-Model (SM) Higgs boson in gluon fusion in hadronic collisions and compute the QCD corrections up to next-to-next-to-leading order (NNLO) and match them to parton showers (NNLO+PS). The complete dependence on the top-quark mass is taken into account without making any approximations to the top quark loops mediating the coupling between the gluons and the Higgs boson. To this end, we have included the $gg\to H$ amplitudes up to three loops and the $pp\to H$+jet amplitudes up to two loops in the full SM theory. This is the first fully differential calculation of the top-quark mass effects up to NNLO in QCD, and we study their impact on relevant observables for the LHC.

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arXiv2024

NNLO+PS predictions for Higgs production through bottom-quark fusion

We present next-to-next-to-leading-order (NNLO) QCD corrections for Higgs production through bottom-quark annihilation (\bbH{}) matched to parton showers (NNLO+PS) using the \minnlo{} technique. The \minnlo{} method is adapted for the extra scale dependence due to the Yukawa coupling renormalized in the $\overline{\rm MS}$ scheme. The computation has been carried out in the five flavour scheme (5FS) neglecting the bottom mass. Results are compared against fixed-order predictions at NNLO and resummed predictions at next-to-next-to-leading-logarithmic (NNLL) accuracy. We also present preliminary results within the four-flavour scheme (4FS) setup, reaching a new level of precision in the massive scheme.

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arXiv2024

Next-to-next-to-leading order event generation for Z-boson production in association with a bottom-quark pair

We consider the production of a Z boson decaying to leptons in association with a bottom-quark pair in hadronic collisions. For the first time, we compute predictions at next-to-next-to-leading order (NNLO) in QCD, and we combine them with the all-orders radiative corrections from a parton-shower simulation (NNLO+PS). Our method represents the first approach to NNLO+PS event generation applicable to processes featuring a colour singlet and a heavy-quark pair in the final state. The novel two-loop corrections are computed for massless bottom quarks, and the leading mass corrections are restored through a small-mass expansion. The calculation is carried out in the four-flavour scheme, and we find that the sizeable NNLO QCD corrections lift the long-standing tension between lower-order predictions in four- and five-flavour schemes. Our predictions are compared to a CMS measurement for Z boson plus b-jet production, achieving an excellent description of the data.

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arXiv2024

Ad interim recommendations for the Higgs boson production cross sections at $\sqrt{s} = 13.6$ TeV

This note documents predictions for the inclusive production cross sections of the Standard Model Higgs boson at the Large Hadron Collider at a centre of mass energy of 13.6 TeV. The predictions here are based on simple extrapolations of previously documented predictions published in the CERN Yellow Report "Deciphering the Nature of the Higgs Sector". The predictions documented in this note should serve as a reference while a more complete and update-to-date derivation of cross section predictions is in progress.

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arXiv2024

NNLO+PS predictions for Higgs production through bottom-quark annihilation with MINNLO$_{\text{PS}}$

We consider Higgs production through bottom-quark annihilation at hadron colliders and we calculate next-to-next-to-leading-order (NNLO) corrections in QCD perturbation theory matched to parton showers (NNLO+PS). To this end, we have adapted the MINNLO$_{\text{PS}}$ method to account for the extra scale dependence induced by an overall Yukawa coupling that is $\overline{\rm MS}$ renormalized. We compare our results against state-of-the-art fixed-order predictions at NNLO as well as resummed predictions at next-to-next-to-leading-logarithmic (NNLL) accuracy.

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arXiv2024

Jettiness formulation of the MINNLO$_{\text{PS}}$ method

We present a new formulation of the MINNLO method to match NNLO QCD calculations with parton showers by using jettiness as a resummation variable. The full derivation for colour-singlet processes is presented using $0$-jettiness starting from the NNLL$^\prime$ resummation formula. We show phenomenological results for Drell-Yan and Higgs-boson production at the LHC and compare our predictions to ATLAS and CMS data. Differences to the original MINNLO formulation using the transverse momentum of the colour singlet as resummation variable are discussed. We further present a comparison of MINNLO predictions with GENEVA. Finally, we extend the formulation of the MINNLO method to 1-jettiness which is applicable to processes with a colour singlet plus one jet in the final state.

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arXiv2023

Taming a leading theoretical uncertainty in HH measurements via accurate simulations for bbH production

We present a new simulation for Higgs boson production in association with bottom quarks ($b\bar{b}H$) at next-to-leading order (NLO) accuracy matched to parton showers in hadronic collisions. Both contributions, the standard one proportional to the bottom-quark Yukawa coupling and the loop-induced one proportional to the top-quark Yukawa coupling from the gluon-fusion process, are taken into account in a scheme with massive bottom quarks. Therefore, we provide the full simulation of the $b\bar{b}H$ final state in the Standard Model, which constitutes also a crucial background to measurements for Higgs-boson pair ($HH$) production at the Large Hadron Collider when at least one of the Higgs bosons decays to bottom quarks. So far, the modeling of the $b\bar{b}H$ final state induced one of the dominant theoretical uncertainties to $HH$ measurements, as the gluon-fusion component was described only at the leading order (LO) with uncertainties of $\mathcal{O}(100\%)$. Including NLO corrections in its simulation allows us to reduce the scale dependence to $\mathcal{O}(50\%)$ so that it becomes subdominant with respect to other systematic uncertainties. As a case study, we provide an in-depth analysis of the $b\bar{b}H$ background to $HH$ measurements with realistic selection cuts in the $2b2γ$ channel. We also compare our novel simulation with the currently-employed ones, discussing possible issues and shortcomings of a scheme with massless bottom quarks. Finally, we propagate the effect of the new $b\bar{b}H$ simulation to $HH$ searches in the $2b2γ$ and $2b2τ$ final states, and we find an improvement of up to 10% (20%) on the current (HL-LHC) limits on the $HH$ cross section.

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arXiv2023

B-hadron production at the LHC from bottom-quark pair production at NNLO+PS

The production of B hadrons is among the most abundant fundamental QCD processes measured at the LHC. We present for the first time predictions for this process accurate to next-to-next-to-leading order in QCD perturbation theory by simulating bottom-quark pair production at this accuracy matched to parton showers. Our novel results are in good agreement with experimental data for the production of different types of B hadrons from ATLAS, CMS and LHCb at 7 TeV and/or 13 TeV, including various fiducial cross sections as well as single- and double-differential distributions, and 13 TeV/7 TeV cross-section ratios.

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arXiv2022

$W^\pm Z$ production at NNLO QCD and NLO EW matched to parton showers with MiNNLO$_{\rm PS}$

We consider $W^\pm Z$ production in hadronic collisions and present high-precision predictions in QCD and electroweak (EW) perturbation theory matched to parton showers. To this end, we match next-to-next-to-leading order QCD corrections to parton showers using the MiNNLO$_{\rm PS}$ method and consistently combine them with next-to-leading order EW corrections matched to parton showers. This is the first time such accuracy in the event generation is achieved for any collider process, and we study in detail the impact of different choices in the combination of QCD and EW corrections as well as QCD and QED showers. Spin correlations, interferences and off-shell effects are retained by considering the full leptonic processes $pp \to \ell^+\ell^-\ell'^\pm ν_\ell'$ with $\ell'\neq\ell$ and $\ell'=\ell$ without approximations, and the matching to QED radiation is performed preserving the resonance structure of the process. We find that NNLO QCD predictions including QCD and QED shower effects provide a very good approximation in the bulk-region of the phase space, while EW effects become increasingly important in the high-energy tails of kinematic distributions. Our default predictions are in excellent agreement with recent ATLAS data.

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arXiv2022

Linear power corrections for two-body kinematics in the $q_T$ subtraction formalism

Transverse-momentum cuts on undistinguished particles in two-body final states induce an enhanced sensitivity to low momentum scales. This undesirable feature, which ultimately leads to an instability of the fixed-order series, poses additional challenges to non-local subtraction schemes. In this letter, we address this issue for general colour-singlet processes within the $q_T$-subtraction formalism, focussing on neutral-current Drell-Yan production. We present a simple procedure to reduce the dependence on the slicing parameter from linear to quadratic, by accounting for the linear power corrections through an appropriate recoil prescription. We observe a dramatical improvement of the numerical convergence and a reduction of the systematic uncertainties. We also discuss how a linear dependence in $q_T$ can be avoided for Drell-Yan production by using staggered cuts, which, to the best of our understanding, could be used in experimental analyses. We show that our approach can be successfully applied also to on-shell $ZZ$ production. We finally study diphoton production and verify that our approach is insufficient to capture the linear power corrections introduced by the isolation procedure. The recoil prescription is available in version 2.1 of MATRIX.

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arXiv2022

NNLO event generation for $\boldsymbol{pp \to Zh \to \ell^+\ell^- b \bar b}$ production in the SM effective field theory

We consider associated $Zh$ production with $Z \to \ell^+ \ell^-$ and $h \to b \bar b$ decays in hadronic collisions. In the framework of the Standard Model effective field theory (SMEFT) we calculate the QCD corrections to this process and achieve next-to-next-to-leading order plus parton shower (NNLO$+$PS) accuracy using the MiNNLO$_{\rm PS}$ method. This precision is obtained for a subset of six SMEFT operators, including the corrections from effective Yukawa- and chromomagnetic dipole-type interactions. Missing higher-order QCD effects associated with the considered dimension-six operators are estimated to have a relative numerical impact of less than a percent on the total rate once existing experimental limits on the relevant Wilson coefficients are taken into account. We provide a dedicated Monte Carlo (MC) code that evaluates the NNLO SMEFT corrections on-the-fly in the event generation. This MC generator is used to study the numerical impact of NNLO$+$PS corrections on the kinematic distributions in $pp \to Zh \to \ell^+ \ell^- b \bar b$ production employing simple SMEFT benchmark scenarios. We identify the invariant mass $m_{b \bar b}$ of the two $b$-tagged jets as well as the three-invariant jet mass $m_{b \bar b j}$ as particularly interesting observables to study SMEFT effects. These distributions receive contributions that change both their normalisation and shape with the latter modifications depending on the exact jet definition. To our knowledge SMEFT effects of this type have so far not been discussed in the literature. The presented MC generator can also serve as a starting point to obtain NNLO$+$PS accuracy for a suitable enlarged set of effective operators in the future.

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arXiv2022

Next-to-next-to-leading order event generation for $VH$ production with $H\to b\bar{b}$ decay

We consider the Higgsstrahlung process in hadronic collisions and present the computation of next-to-next-to-leading order predictions matched to parton showers for both production and $H\to b\bar{b}$ decay employing the MiNNLO$_{\rm PS}$ method. We present predictions for $ZH$ and $W^{\pm}H$ production including spin correlations and off-shell effects by calculating the full processes $pp \to \ell^+\ell^-H \to \ell^+\ell^-b\bar{b}$, $pp \to ν_\ell\barν_\ell H \to ν_\ell\barν_\ell b\bar{b}$ and $pp \to \ell^\pm ν_\ell H \to \ell^\pm ν_\ell b\bar{b}$ in the narrow-width approximation for the Higgs boson. For the $W^{\pm}H$ process, NNLO+PS accuracy in production and decay is achieved for the first time. Our calculations are validated against earlier simulations in the NNLOPS approach that includes NNLO corrections via multi-differential reweighting. The new MiNNLO$_{\rm PS}$ generators for these processes, which evaluate NNLO corrections on-the-fly in the event generation, will supersede those earlier calculations. Our predictions are in good agreement with recent measurements of the Higgsstrahlung cross sections.

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