arXiv subjects

Jürgen Reuter

Publications and source records attributed to Jürgen Reuter.

At least 37 records · Page 2Linked to original sources

arXiv2022

Precision test of the muon-Higgs coupling at a high-energy muon collider

We explore the sensitivity of directly testing the muon-Higgs coupling at a high-energy muon collider. This is strongly motivated if there exists new physics that is not aligned with the Standard Model Yukawa interactions which are responsible for the fermion mass generation. We illustrate a few such examples for physics beyond the Standard Model. With the accidentally small value of the muon Yukawa coupling and its subtle role in the high-energy production of multiple (vector and Higgs) bosons, we show that it is possible to measure the muon-Higgs coupling to an accuracy of ten percent for a 10 TeV muon collider and a few percent for a 30 TeV machine by utilizing the three boson production, potentially sensitive to a new physics scale about $Λ\sim$ 30-100 TeV.

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arXiv2022

Report of the Topical Group on Electroweak Precision Physics and Constraining New Physics for Snowmass 2021

The precise measurement of physics observables and the test of their consistency within the standard model (SM) are an invaluable approach, complemented by direct searches for new particles, to determine the existence of physics beyond the standard model (BSM). Studies of massive electroweak gauge bosons (W and Z bosons) are a promising target for indirect BSM searches, since the interactions of photons and gluons are strongly constrained by the unbroken gauge symmetries. They can be divided into two categories: (a) Fermion scattering processes mediated by s- or t-channel W/Z bosons, also known as electroweak precision measurements; and (b) multi-boson processes, which include production of two or more vector bosons in fermion-antifermion annihilation, as well as vector boson scattering (VBS) processes. The latter categories can test modifications of gauge-boson self-interactions, and the sensitivity is typically improved with increased collision energy. This report evaluates the achievable precision of a range of future experiments, which depend on the statistics of the collected data sample, the experimental and theoretical systematic uncertainties, and their correlations. In addition it presents a combined interpretation of these results, together with similar studies in the Higgs and top sector, in the Standard Model effective field theory (SMEFT) framework. This framework provides a model-independent prescription to put generic constraints on new physics and to study and combine large sets of experimental observables, assuming that the new physics scales are significantly higher than the EW scale.

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arXiv2022

Automated NLO SM corrections for all colliders

We summarize the status of automated NLO SM corrections for hadron and lepton collider processes in the multi-purpose event generator WHIZARD. The focus will be on NLO EW and QCD-EW mixed corrections at the LHC. Also, recent progress on the inclusion of EW corrections in future lepton collider processes and on the POWHEG-matched event generation in the NLO automated setup will be discussed.

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arXiv2022

NLO Electroweak Corrections to Multi-Boson Processes at a Muon Collider

We present results on NLO electroweak (EW) corrections to multiple massive boson production processes at a future muon collider. Inclusive cross sections with $\mathcal{O}(α)$ corrections for processes for up to four bosons in the final state as well as differential distributions for $HZ$ production are computed for $\sqrt{s}=3$, $10$ and $14$ TeV by using FKS subtraction in the NLO EW automated Monte-Carlo framework WHIZARD+RECOLA. Large logarithmic effects due to collinear ISR and EW virtual correction factors as well as the impacts of an energy cut on hard photons are discussed with an emphasis on the properties of Higgsstrahlung. The potential of a proposed muon collider for studying physics of the EW sector is underlined by the EW corrections significantly affecting observables for processes at high energies and boson multiplicities.

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arXiv2022

Precision Test of the Muon-Higgs Coupling at a High-energy Muon Collider

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arXiv2022

Heavy neutrinos at future linear e$^+$e$^-$ colliders

Neutrinos are among the most mysterious particles in nature. Their mass hierarchy and oscillations, as well as their antiparticle properties, are being intensively studied in experiments around the world. Moreover, in many models of physics beyond the Standard Model, the baryon asymmetry or the dark matter density in the Universe are explained by introducing new species of neutrinos. Among others, heavy neutrinos of Dirac or Majorana nature were proposed to solve open questions in High Energy Physics. Such neutrinos with masses above the EW scale could be produced at future linear e$^+$e$^-$ colliders, like the Compact LInear Collider (CLIC) or the International Linear Collider (ILC). We studied the possibility of observing decays of heavy Dirac and Majorana neutrinos in the $qq\ell$ final state with ILC running at 500 GeV and 1 TeV, and CLIC at 3 TeV. The analysis is based on the Whizard event generation and fast simulation of detector response with Delphes. Neutrinos with masses from 200 GeV to 3.2 TeV were considered. We estimated the limits on the production cross sections, interpreted them in terms of the neutrino-lepton coupling parameter $V_{\ell N}^{2}$ (effectively the neutrino mixing angle) and compared them with current limits coming from the LHC running at 13 TeV, as well as the expected limits from future hadron colliders. The limits for the future lepton colliders, extending down to the coupling values of $10^{-7} - 10^{-6}$, are stricter than any other limit estimates published so far.

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arXiv2022

Muon Collider Physics Summary

The perspective of designing muon colliders with high energy and luminosity, which is being investigated by the International Muon Collider Collaboration, has triggered a growing interest in their physics reach. We present a concise summary of the muon colliders potential to explore new physics, leveraging on the unique possibility of combining high available energy with very precise measurements.

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arXiv2022

The physics case of a 3 TeV muon collider stage

In the path towards a muon collider with center of mass energy of 10 TeV or more, a stage at 3 TeV emerges as an appealing option. Reviewing the physics potential of such muon collider is the main purpose of this document. In order to outline the progression of the physics performances across the stages, a few sensitivity projections for higher energy are also presented. There are many opportunities for probing new physics at a 3 TeV muon collider. Some of them are in common with the extensively documented physics case of the CLIC 3 TeV energy stage, and include measuring the Higgs trilinear coupling and testing the possible composite nature of the Higgs boson and of the top quark at the 20 TeV scale. Other opportunities are unique of a 3 TeV muon collider, and stem from the fact that muons are collided rather than electrons. This is exemplified by studying the potential to explore the microscopic origin of the current $g$-2 and $B$-physics anomalies, which are both related with muons.

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arXiv2022

Vector Boson Scattering Processes: Status and Prospects

Insight into the electroweak (EW) and Higgs sectors can be achieved through measurements of vector boson scattering (VBS) processes. The scattering of EW bosons are rare processes that are precisely predicted in the Standard Model (SM) and are closely related to the Higgs mechanism. Modifications to VBS processes are also predicted in models of physics beyond the SM (BSM), for example through changes to the Higgs boson couplings to gauge bosons and the resonant production of new particles. In this review, experimental results and theoretical developments of VBS at the Large Hadron Collider, its high luminosity upgrade, and future colliders are presented.

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arXiv2021

Theory requirements for SM Higgs and EW precision physics at the FCC-ee

High precision experimental measurements of the properties of the Higgs boson at $\sim$ 125 GeV as well as electroweak precision observables such as the W -boson mass or the effective weak leptonic mixing angle are expected at future $e^+e^-$ colliders such as the FCC-ee. This high anticipated precision has to be matched with theory predictions for the measured quantities at the same level of accuracy. We briefly summarize the status of these predictions within the Standard Model (SM) and of the tools that are used for their determination. We outline how the theory predictions will have to be improved in order to reach the required accuracy, and also comment on the simulation frameworks for the Higgs and EW precision program.

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arXiv2021

WHIZARD 3.0: Status and News

This article summarizes the talk given at the LCWS 2021 conference on the status and news of the WHIZARD Monte Carlo event generator. We presented its features relevant for the physics program of future lepton and especially linear colliders as well as recent developments towards including NLO perturbative corrections and a UFO interface to study models beyond the Standard Model. It takes as reference the version 3.0.0$β$ released in August 2020 and additionally discusses the developments that will be included in the next major version 3.0.0 to be released in April 2021.

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arXiv2020

Beyond the Standard Model in Vector Boson Scattering Signatures

The high-energy scattering of massive electroweak bosons, known as vector boson scattering (VBS), is a sensitive probe of new physics. VBS signatures will be thoroughly and systematically investigated at the LHC with the large data samples available and those that will be collected in the near future. Searches for deviations from Standard Model (SM) expectations in VBS facilitate tests of the Electroweak Symmetry Breaking (EWSB) mechanism. Current state-of-the-art tools and theory developments, together with the latest experimental results, and the studies foreseen for the near future are summarized. A review of the existing Beyond the SM (BSM) models that could be tested with such studies as well as data analysis strategies to understand the interplay between models and the effective field theory paradigm for interpreting experimental results are discussed. This document is a summary of the EU COST network "VBScan" workshop on the sensitivity of VBS processes for BSM frameworks that took place December 4-5, 2019 at the LIP facilities in Lisbon, Portugal. In this manuscript we outline the scope of the workshop, summarize the different contributions from theory and experiment, and discuss the relevant findings.

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arXiv2020

Status of the WHIZARD generator for linear colliders

This summarizes the talk given at the LCWS 2019 conference in Sendai, Japan, on the progress of the WHIZARD event generator in terms of new physics features and technical improvements relevant for the physics programme of future lepton and especially linear colliders. It takes as a reference the version 2.8.2 released in October 2019, and also takes into account the development until version 2.8.3 to be released in February 2020.

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arXiv2019

Proposal for the validation of Monte Carlo implementations of the standard model effective field theory

We propose a procedure to cross-validate Monte Carlo implementations of the standard model effective field theory. It is based on the numerical comparison of squared amplitudes computed at specific phase-space and parameter points in pairs of implementations. Interactions are fully linearised in the effective field theory expansion. The squares of linear effective field theory amplitudes and their interference with standard-model contributions are compared separately. Such pairwise comparisons are primarily performed at tree level and a possible extension to the one-loop level is also briefly considered. We list the current standard model effective field theory implementations and the comparisons performed to date.

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arXiv2019

VBSCan Thessaloniki 2018 Workshop Summary

This document reports the first year of activity of the VBSCan COST Action network, as summarised by the talks and discussions happened during the VBSCan Thessaloniki 2018 workshop. The VBSCan COST action is aiming at a consistent and coordinated study of vector-boson scattering from the phenomenological and experimental point of view, for the best exploitation of the data that will be delivered by existing and future particle colliders.

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arXiv2018

Parallel Adaptive Monte Carlo Integration with the Event Generator WHIZARD

We describe a new parallel approach to the evaluation of phase space for Monte-Carlo event generation, implemented within the framework of the WHIZARD package. The program realizes a twofold self-adaptive multi-channel parameterization of phase space and makes use of the standard OpenMP and MPI protocols for parallelization. The modern MPI3 feature of asynchronous communication is an essential ingredient of the computing model. Parallel numerical evaluation applies both to phase-space integration and to event generation, thus covering the most computing-intensive parts of physics simulation for a realistic collider environment.

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arXiv2018

The Role of Positron Polarization for the initial 250 GeV stage of the ILC

The International Linear Collider is now proposed with a staged machine design, with the first stage at $\sqrt{s}=250$ GeV and an integrated luminosity goal of 2 ab${}^{-1}$. One of the questions for the machine design is the importance of positron polarization. In this report, we review the impact of positron polarization on the physics goals of the 250 GeV stage of the ILC and demonstrate that positron polarization has distinct advantages.

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arXiv2018

Exclusive Top Threshold Matching at Lepton Colliders

The threshold scan at future lepton colliders is the most precise known method to determine the top quark mass (well below 100 MeV), a fundamental parameter of the Standard Model that co-determines the stability properties of the electroweak vacuum. We present a new method to match the continuum next-to-leading order QCD corrections with the next-to-leading logarithmic resummation of the Coulomb singularities of the quasi-toponium bound state at threshold where fixed-order perturbation theory is invalid. This matching is performed at the level of the fully exclusive $W^+bW^-\bar{b}$ final state. It allows to study all kinds of differential distributions at or close to threshold. The top mass dependence of these distributions opens up new possibilities for the top mass determination that might be competitive with the inclusive threshold scan.

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