This note presents constraints on Standard Model parameters using published and preliminary precision electroweak results obtained at the electron-positron colliders LEP and SLC. The results are compared with precise electroweak measurements from other experiments, notably CDF and DØ at the Tevatron. Constraints on the input parameters of the Standard Model are derived from the combined set of results obtained in high-$Q^2$ interactions, and used to predict results in low-$Q^2$ experiments, such as atomic parity violation, Møller scattering, and neutrino-nucleon scattering. The main changes with respect to the experimental results presented in 2009 are new combinations of results on the width of the W boson and the mass of the top quark.
We present results from electroweak precision measurements at CDF. These include the measurement of the Z boson rapidity distribution using di-electron events, the W boson charge asymmetry measurement in the electron-neutrino decay and the direct measurement of the W boson mass and width in both the electron-neutrino and muon-neutrino decay channels.
An overview of recent results on electroweak precision measurements from the CMS Collaboration is presented. Studies of the weak boson differential transverse momentum spectra, Z boson angular coefficients, forward-backward asymmetry of Drell-Yan lepton pairs and charge asymmetry of W boson production are made in comparison to the state-of-the-art Monte Carlo generators and theoretical predictions. The results show a good agreement with the Standard Model. As a proof of principle for future W mass measurements, a W-like analysis of the Z boson mass is performed.
This note presents constraints on Standard Model parameters using published and preliminary precision electroweak results measured at the electron-positron colliders LEP and SLC. The results are compared with precise electroweak measurements from other experiments, notably CDF and DØat the Tevatron. Constraints on the input parameters of the Standard Model are derived from the combined set of results obtained in high-$Q^2$ interactions, and used to predict results in low-$Q^2$ experiments, such as atomic parity violation, Møller scattering, and neutrino-nucleon scattering. The main changes wit…
Future electroweak precision measurements in the Circular Electron Positron Collider (CEPC) project would significantly improve the precision of electroweak oblique parameters. We evaluate the expected precision through global fits, and study the corresponding sensitivity to weakly interacting fermionic dark matter. Three models with electroweak multiplets in the dark sector are investigated as illuminating examples. We find that the CEPC data can probe up to TeV scales and explore some regions where direct detection cannot reach, especially when the models respect the custodial symmetry.
After reviewing the key features of the global electroweak fit, I will provide updated results and offer experimental and theoretical contexts. I will also make the case for greater precision and highlight future directions.
Several new physics scenarios, motivated e.g. by dark matter, feature new electroweakly charged states where the lightest particle in the multiplet is stable and neutral. In such cases direct searches at LHC are notoriously difficult, while electroweak precision tests both at hadron and lepton colliders offer the possibility to indirectly probe those states. In this work, we assess the sensitivity of the high-luminosity phase of the LHC on new electroweak multiplets via the modification of neutral and charged Drell-Yan processes, and compare the reach of future hadron and lepton colliders pres…
The global fit of the Standard Model predictions to electroweak precision data, which has been routinely performed in the past decades by several groups, led to the prediction of the top quark and the Higgs boson masses before their respective discoveries. With the measurement of the Higgs boson mass at the Large Hadron Collider (LHC) in 2012 by the ATLAS and CMS collaborations, the last free parameter of the Standard Model of particle physics has been fixed, and the global electroweak fit can be used to test the full internal consistency of the electroweak sector of the Standard Model and con…
Anomalous interactions involving the top quark contribute to some of the most difficult observables to directly access experimentally. They can give however a sizeable correction to very precisely measured observables at the loop level. Using a model-independent effective Lagrangian approach, we present the leading indirect constraints on dimension-six effective operators involving the top quark from electroweak precision data. They represent the most stringent constraints on these interactions, some of which may be directly testable in future colliders.
The prospects for electroweak precision measurements at the Future Circular Collider with electron-positron beams (FCC-ee) are discussed. The Z mass and width, as well as the value of the electroweak mixing angle, can be measured with very high precision at the Z pole thanks to an instantaneous luminosity five to six order of magnitudes larger than LEP. At centre-of-mass energies around 160 GeV, corresponding to the WW production threshold, the W mass can be determined very precisely with high-statistics cross section measurements at several energy points. Similarly, a very precise determinati…
Due to the high anticipated experimental precision at the Future Circular Collider FCC-ee (or other proposed $e^+e^-$ colliders, such as ILC, CLIC, or CEPC) for electroweak and Higgs-boson precision measurements, theoretical uncertainties may have, if unattended, an important impact on the interpretation of these measurements within the Standard Model (SM), and thus on constraints on new physics. Current theory uncertainties, which would dominate the total uncertainty, need to be strongly reduced through future advances in the calculation of multi-loop radiative corrections together with impro…
We revisit the global fit to electroweak precision observables in the Standard Model and present model-independent bounds on several general new physics scenarios. We present a projection of the fit based on the expected experimental improvements at future $e^+ e^-$ colliders, and compare the constraining power of some of the different experiments that have been proposed. All results have been obtained with the HEPfit code.
The measurements carried out at LEP and SLC projected us into the precision era of electroweak physics. This has also been relevant in the theoretical interpretation of LHCb and Belle measurements of rare $B$ semileptonic decays, paving the road for new physics with the inference of lepton universality violation in $R_{K^{(*)}}$ ratios. The simplest explanation of these flavour anomalies -- sizeable one-loop contributions respecting Minimal Flavour Violation -- is currently disfavoured by electroweak precision data. In this work, we discuss how to completely relieve the present tension between…
While it is known that third family hypercharge models can explain the neutral current $B-$anomalies, it was hitherto unclear whether the $Z-Z^\prime$ mixing predicted by such models could simultaneously fit electroweak precision observables. Here, we perform global fits of several third family hypercharge models to a combination of electroweak data and those data pertinent to the neutral current $B-$anomalies. While the Standard Model is in tension with this combined data set with a $p-$value of $.00068$, simple versions of the models (fitting two additional parameters each) provide much impr…
The observed Higgs boson mass and the naturalness argument leave us a narrow window for the soft mass spectrum in natural supersymmetry that can be studied through the electroweak precision tests (EWPTs). We divide the analysis into the Higgs sector constrained by the charged Higgs mass bound, the neutralino-chargino sector constrained by the chargino mass bound, and the third-generation squark sector tightly constrained by the observed Higgs mass. Total contributions to EWPTs in the MSSM and NMSSM are both presented. It turns out that natural MSSM is excluded at 68\% CL but consistent at 95\%…
We analyze various models with an extra U(1) gauge symmetry in addition to the Standard Model (SM) gauge group at low energies, and impose limits on the mass of the neutral Z' boson, M_Z', predicted in all such models, and on the Z-Z' mixing angle, theta_ZZ'. The precision electroweak data strongly constrain theta_ZZ' to very small values and for most models we find lower limits on M_Z' of order 1 TeV. In one case we obtain a somewhat better fit than in the SM (although this is only marginally statistically significant) and here we find a weak upper limit at the 90% C.L.
The proposed electron-proton collider experiments LHeC and FCC-eh at CERN are the highest resolution microscopes that can be realised in the present century and they would represent a really unique research facility. We exploit simulated neutral-current and charged-current deep-inelastic scattering data of the LHeC and the FCC-eh and examine their sensitivity for precision physics in the Electroweak sector of the Standard Model (SM), like the effective weak mixing angle $\sin^2θ_{\textrm{W},\ell}^\textrm{eff}$, or the light-quark weak-neutral-current couplings. Unique measurements are further …
