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Andreas Hoecker

Publications and source records attributed to Andreas Hoecker.

At least 19 recordsLinked to original sources
arXiv2026

The Higgs boson through the lens of electroweak precision data

The global electroweak fit tests the quantum structure of the Standard Model by confronting precision measurements with high-order theoretical predictions. This paper presents an updated Gfitter analysis using the latest experimental inputs, notably the new world average of the $W$-boson mass, and state-of-the-art theoretical calculations. The fit yields indirect determinations of precision observables, including the $W$ and Higgs-boson masses, the top-quark mass, and the effective leptonic weak mixing angle, confirming the remarkable internal consistency of the Standard Model. The analysis is further extended to the Higgs sector by combining ATLAS and CMS signal-strength measurements with electroweak precision data in the $\kappa$ framework. The resulting electroweak constraints on the Higgs couplings to vector bosons allow a determination of the total Higgs-boson width with a precision of about 10\% or better within a leading-logarithmic oblique interpretation, and provide bounds on invisible and undetected Higgs-boson branching fractions without using direct searches for invisible Higgs decays. The paper also presents bounds on Wilson coefficients in the Standard Model Effective Field Theory together with projections for the precision of the global electroweak fit achievable at the FCC-ee.

hep-ph↗
arXiv2022

Status of the global electroweak fit with Gfitter in the light of new precision measurements

We present results from the global electroweak fit to precision measurements in the Standard Model (SM). The fit uses the latest theoretical calculations for observables on the $Z$ pole and the $W$ boson mass, yielding precise SM predictions for the effective weak mixing angle and the masses of the $W$ and Higgs bosons, as well as the top quark. We study the impact of the latest measurements on the fit and provide comparisons of the resulting predictions for individual observables with recent measurements.

hep-ph↗
arXiv2021

A continuous integration and web framework in support of the ATLAS Publication Process

The ATLAS collaboration defines methods, establishes procedures, and organises advisory groups to manage the publication processes of scientific papers, conference papers, and public notes. All stages are managed through web systems, computing programs, and tools that are designed and developed by the collaboration. A framework called FENCE is integrated into the CERN GitLab software repository, to automatically configure workspaces where each analysis can be documented by the analysis team and managed by the relevant coordinators. Continuous integration is used to guide the writers in applying consistent and correct formatting when preparing papers to be submitted to scientific journals. Additional software assures the correctness of other aspects of each paper, such as the lists of collaboration authors, funding agencies, and foundations. The framework and the workflow therein provide automatic and easy support to the researchers and facilitates each phase of the publication process, allowing authors to focus on the article contents. The framework and its integration with the most up to date and efficient tools has consequently provided a more professional and efficient automatized work environment to the whole collaboration.

cs.DL↗
arXiv2018

Update of the global electroweak fit and constraints on two-Higgs-doublet models

We present an update of the global fit of the Standard Model electroweak sector to latest experimental results. We include new kinematic top quark and $W$ boson mass measurements from the LHC, a $\sin^2θ^{\ell}_{\mathrm{eff}}$ result from the Tevatron, and a new evaluation of the hadronic contribution to $α(M_Z^2)$. We present tests of the internal consistency of the electroweak Standard Model and updated numerical predictions of key observables. The electroweak data combined with measurements of the Higgs boson coupling strengths and flavour physics observables are used to constrain parameters of two-Higgs-doublet models.

hep-ph↗
arXiv2017

Update of the ALEPH non-strange spectral functions from hadronic $τ$ decays

An update of the ALEPH non-strange spectral functions from hadronic $τ$ decays is presented. Compared to the 2005 ALEPH publication, the main improvement is related to the use of a new method to unfold the measured mass spectra from detector effects. This procedure also corrects a previous problem in the correlations between the unfolded mass bins. Results from QCD studies and for the evaluation of the hadronic vacuum polarisation contribution to the anomalous muon magnetic moment are derived using the new spectral functions. They are found in agreement with published results based on the previous set of spectral functions.

hep-ex↗
arXiv2017

Reevaluation of the hadronic vacuum polarisation contributions to the Standard Model predictions of the muon g-2 and alpha(mZ) using newest hadronic cross-section data

We reevaluate the hadronic vacuum polarisation contributions to the muon magnetic anomaly and to the running of the electromagnetic coupling constant at the Z-boson mass. We include newest e+e- to hadrons cross-section data (among others) from the BABAR and VEPP-2000 experiments. For the muon (g-2)/2 we find for the lowest-order hadronic contribution (693.1 +- 3.4) 10^-10, improving the precision of our previous evaluation by 21%. The full Standard Model prediction differs by 3.5 sigma from the experimental value. The five-quark hadronic contribution to alpha(mZ) is evaluated to be (276.0 +- 0.9) 10^-4.

hep-ph↗
arXiv2012

Charged-Lepton Flavour Physics

This writeup of a talk at the 2011 Lepton-Photon symposium in Mumbai, India, summarises recent results in the charged-lepton flavour sector. I review searches for charged-lepton flavour violation, lepton electric dipole moments and flavour-conserving CP violation. I also discuss recent progress in tau-lepton physics and in the Standard Model prediction of the muon anomalous magnetic moment.

hep-ph↗
arXiv2011

SVD-based unfolding: implementation and experience

With the first year of data taking at the LHC by the experiments, unfolding methods for measured spectra are reconsidered with much interest. Here, we present a novel ROOT-based implementation of the Singular Value Decomposition approach to data unfolding, and discuss concrete analysis experience with this algorithm.

physics.data-an↗
arXiv2011

Reevaluation of the Hadronic Contributions to the Muon g-2 and to alpha(MZ)

We reevaluate the hadronic contributions to the muon magnetic anomaly, and to the running of the electromagnetic coupling constant at the Z-boson mass. We include new pi+pi- cross-section data from KLOE, all available multi-hadron data from BABAR, a reestimation of missing low-energy contributions using results on cross sections and process dynamics from BABAR, a reevaluation of all experimental contributions using the software package HVPTools, together with a reanalysis of inter-experiment and inter-channel correlations, and a reevaluation of the continuum contributions from perturbative QCD at four loops. These improvements lead to a decrease in the hadronic contributions with respect to earlier evaluations. For the muon g-2 we find lowest-order hadronic contributions of (692.3 +- 4.2) 10^-10 and (701.5 +- 4.7) 10^-10 for the e+e- based and tau-based analyses, respectively, and full Standard Model predictions that differ by 3.6 sigma and 2.4 sigma from the experimental value. For the e+e- based five-quark hadronic contribution to alpha(MZ) we find Delta_alpha_had[5](MZ)=(275.7 +- 1.0) 10^-4. The reduced electromagnetic coupling strength at MZ leads to an increase by 7 GeV in the most probable Higgs boson mass obtained by the standard Gfitter fit to electroweak precision data.

hep-ph↗
arXiv2011

Revisiting the Global Electroweak Fit of the Standard Model and Beyond with Gfitter

The global fit of the Standard Model to electroweak precision data, routinely performed by the LEP electroweak working group and others, demonstrated impressively the predictive power of electroweak unification and quantum loop corrections. We have revisited this fit in view of (i) the development of the new generic fitting package Gfitter, (ii) the insertion of constraints from direct Higgs searches at LEP and the Tevatron, and (iii) a more thorough statistical interpretation of the results. Gfitter is a modular fitting toolkit, which features predictive theoretical models as independent plugins, and a statistical analysis of the fit results using toy Monte Carlo techniques. The state-of-the-art electroweak Standard Model is fully implemented, as well as generic extensions to it. This paper introduces the Gfitter project, and presents state-of-the-art results for the global electroweak fit in the Standard Model, and for a model with an extended Higgs sector (2HDM). Numerical and graphical results for fits with and without including the constraints from the direct Higgs searches at LEP and Tevatron are given. Perspectives for future colliders are analysed and discussed. Including the direct Higgs searches, we find M_H=(116.4 +18.3 -1.3) GeV, and the 2sigma and 3sigma allowed regions [114,145] GeV and [[113,168] and [180,225]] GeV, respectively. For the strong coupling strength at fourth perturbative order we obtain alpha_S(M_Z)=0.1193 +0.0028 -0.0027(exp) +- 0.0001(theo). Finally, for the mass of the top quark, excluding the direct measurements, we find m_t=(178.2 +9.8 -4.2) GeV. In the 2HDM we exclude a charged-Higgs mass below 240 GeV at 95% confidence level. This limit increases towards larger tan(beta), where e.g., M_H+-<780 GeV is excluded for tan(beta)=70.

hep-ph↗
arXiv2010

The Hadronic Contribution to the Muon Anomalous Magnetic Moment and to the Running Electromagnetic Fine Structure Constant at MZ - Overview and Latest Results

Quantum loops induce an anomaly, a_mu, in the magnetic moment of the muon that can be accurately measured. Its Standard Model prediction is limited in precision by contributions from hadronic vacuum polarisation of the photon. The dominant lowest-order hadronic term can be calculated with a combination of experimental cross section data, involving e+e- annihilation to hadrons, and perturbative QCD. These are used to evaluate an energy-squared dispersion integral that strongly emphasises low photon virtualities. The dominant contribution to the integral stems from the two-pion channel that can be measured both in e+e- annihilation and in tau decays. The corresponding e+e- and tau-based predictions of a_mu exhibit deviations by, respectively, 3.6 sigma and 2.4 sigma from experiment, leaving room for a possible interpretation in terms of new physics. This talk reviews the status of the Standard Model prediction with emphasis on the lowest-order hadronic contribution. Also given is the latest result for the running electromagnetic fine structure constant at the Z-mass pole, whose precision is limited by hadronic vacuum polarisation contributions, determined in a way similar to those of the magnetic anomaly.

hep-ph↗
arXiv2009

Status of the global electroweak fit of the Standard Model

Results from the global Standard Model fit to electroweak precision data, including newest Tevatron measurements, are reviewed and discussed. The complete fit using also the constraints from the direct Higgs boson searches yields an upper limit on the Higgs mass of 153 GeV at 95% CL. The top mass is indirectly determined to be (177.2 +10.5 -7.8) GeV and (179.5 +8.8 -5.2) GeV for fits including or not the constraints from the direct Higgs searches, respectively. Using the 3NLO perturbative prediction of the massless QCD Adler function, the strong coupling constant at the Z-mass scale is determined to be alpha_s(MZ)=0.1193 +- 0.0028 +- 0.0001, which is in excellent agreement with the 3NLO result from hadronic tau decays. The perspectives of the electroweak fit for forthcoming and proposed future collider projects are discussed. The available constraints on the Higgs mass are convolved with the high-scale behaviour of the Higgs quartic coupling to derive likelihoods for the survival of the Standard Model versus its cut-off scale evolved up to the Planck mass.

hep-ph↗
arXiv2007

ALEPH Tau Spectral Functions and QCD

Hadronic $τ$ decays provide a clean laboratory for the precise study of quantum chromodynamics (QCD). Observables based on the spectral functions of hadronic $τ$ decays can be related to QCD quark-level calculations to determine fundamental quantities like the strong coupling constant, quark and gluon condensates. Using the ALEPH spectral functions and branching ratios, complemented by some other available measurements, and a revisited analysis of the theoretical framework, the value $\asm = 0.345 \pm 0.004_{\rm exp} \pm 0.009_{\rm th}$ is obtained. Taken together with the determination of \asZ from the global electroweak fit, this result leads to the most accurate test of asymptotic freedom: the value of the logarithmic slope of $α_s^{-1}(s)$ is found to agree with QCD at a precision of 4%. The value of \asZ obtained from $τ$ decays is $\asZ = 0.1215 \pm 0.0004_{\rm exp} \pm 0.0010_{\rm th} \pm 0.0005_{\rm evol} = 0.1215 \pm 0.0012$.

hep-ph↗
arXiv2003

Interpreting CP Asymmetries in B->pi+ pi- Decays

We discuss methods used to interpret the measurements of CP-asymmetry in B->pi+pi- within the framework of the Standard Model. Interpretations using various theoretical inputs are given, ranging from the rather general, yet unpredictive, properties based on strong isospin symmetry to highly predictive calculations using QCD Factorization. The calculations are performed using the software package CKMFitter and a frequentist method, Rfit.

hep-ph↗
arXiv1997

Improved Determination of alpha_QED(M_Z^2) and the Anomalous Magnetic Moment of the Muon

We reevaluate the hadronic contribution to the running of the QED fine structure constant alpha(s) at s = M_Z^2. We use data from e+e- annihilation and tau decays at low energy and at the qq-bar thresholds, where resonances occur. Using so-called spectral moments and the Operator Product Expansion (OPE), it is shown that a reliable theoretical prediction of the hadronic production rate R(s) is available at relatively low energies. Its application improves significantly the precision on the hadronic vacuum polarization contribution. We obtain delta_alpha^had = (277.8 +/- 2.6) x 10^-4 yielding alpha^-1(M_Z^2) = 128.923 +/- 0.036$. Inserting this value in a global electroweak fit using current experimental input, we constrain the mass of the Standard Model Higgs boson to be M_Higgs = (129 +103 -62) GeV. Analogously, we improve the precision of the hadronic contribution to the anomalous magnetic moment of the muon for which we obtain a_mu^had = (695.1 +/- 7.5) x 10^-10.

hep-ph↗