Electroweak Radiative Corrections Research Articles

Hybrid analysis of radiative corrections to neutron decay with current algebra and effective field theory

We introduce a useful framework for high-precision studies of the neutron beta decay by merging the current algebra description and the fixed-order effective field theory calculation of the electroweak radiative corrections to the neutron axial form factor. We discuss the advantages of this hybrid method and show that it only requires a minimal amount of lattice QCD inputs to achieve a 10−4 theory accuracy for the Standard Model prediction of the neutron lifetime and the axial-to-vector coupling ratio λ, both important to the search for physics beyond the Standard Model.

One-Loop Electroweak Radiative Corrections to Polarized e+e– → γZ Process

One-Loop Electroweak Radiative Corrections to Polarized e+e– → γZ Process

GRIFFIN: A C++ library for electroweak radiative corrections in fermion scattering and decay processes

This paper describes a modular framework for the description of electroweak scattering and decay processes, including but not limited to Z-resonance physics. The framework consistently combines a complex-pole expansion near an s-channel resonance with a regular fixed-order perturbative description away from the resonance in a manifestly gauge-invariant scheme. Leading vertex correction contributions are encapsulated in form factors that can be predicted or treated as numerical fit parameters. This framework has been implemented in the publicly available object-oriented C++ library GRIFFIN. Version 1.0 of this library provides Standard Model predictions for the IR-subtracted matrix elements for the process f\bar{f} \to f'\bar{f}'ff‾→f′f‾′ with full NNLO and leading higher-order contributions on the Z-resonance, and with NLO corrections off-resonance. The library can straightforwardly be extended to include higher-order corrections, should they become available, or predictions for new physics models. It can be interfaced with Monte-Carlo programs to account for QED and QCD initial-state and final-state radiation.

The Standard Model Theory of Neutron Beta Decay

We review the status of the Standard Model theory of neutron beta decay. Particular emphasis is put on the recent developments in the electroweak radiative corrections. Given that some existing approaches give slightly different results, we thoroughly review the origin of discrepancies, and provide our recommended value for the radiative correction to the neutron and nuclear decay rates. The use of dispersion relation, lattice Quantum Chromodynamics, and an effective field theory framework allows for high-precision theory calculations at the level of 10−4, turning neutron beta decay into a powerful tool to search for new physics, complementary to high-energy collider experiments. We offer an outlook to the future improvements.

Probing the weak mixing angle at high energies at the LHC and HL-LHC

Measurements of neutral current Drell-Yan production at large invariant dilepton masses can be used to test the energy scale dependence (running) of the electroweak mixing angle. In this work, we make use of a novel implementation of the full next-to-leading order electroweak radiative corrections to the Drell-Yan process using the MS‾ renormalization scheme for the electroweak mixing angle. The potential of future analyses using proton-proton collisions at s=13.6TeV in the Run 3 and High-Luminosity phases of the LHC is explored. In this way, the Standard Model predictions for the MS‾ running at TeV scales can be probed.

Computer package DIZET v. 6.45

The new version of the DIZET electroweak library is described. Changes and additional code features concerning the previous version are explained. The software allows one to make state-of-the-art theoretical predictions for pseudo-observable quantities, including higher-order radiative corrections. The current version of the DIZET library v. 6.45 incorporates advanced recent results of theoretical calculations. Numerical comparisons with the results of the previous version are performed. Estimates of theoretical uncertainties are discussed. Program summaryProgram Title:DIZET version 6.45CPC Library link to program files:https://doi.org/10.17632/2fr58v92xc.1Code Ocean capsule:https://codeocean.com/capsule/0198682Licensing provisions: GPLv3Programming language: FORTRAN 77/90External routines: AlphaQED http://www-com.physik.hu-berlin.de/~fjeger/software.htmlJournal reference of previous version: Comput. Phys. Commun. 59 (1990) 303Does the new version supersede the previous version?: YesReasons for the new version: Implementation of new options.Summary of revisions: Implemented the complete electroweak two-loop radiative corrections to all the relevant electroweak precision pseudo-observables related to the Z-boson decay. Added support of new library for hadronic contribution to vacuum polarization.Nature of problem: The Z-resonance region is still extremely important for the experimental verification of the Standard Model. The anticipated experimental accuracy on a large variety of observables has to be matched with theory predictions of at least the same level of accuracy to achieve maximum usage of experimental data.Solution method: Theoretical calculations at NNLO in perturbation theory allow to compute higher precision pseudo-observables to verify the Standard Model at high luminosity future colliders. The package includes electroweak two-loop corrections calculated in the on-mass shell renormalization scheme. Pseudo-observables and electroweak form-factors can be calculated in a wide range of input parameters.Additional comments including restrictions and unusual features: The estimate of results at the off-resonance region should be treated with caution as two-loop electroweak corrections were calculated for the Z-resonance peak.

Electroweak radiative corrections to polarized top quark pair production

Electroweak radiative corrections to polarized top quark pair production

One-loop radiative corrections to photon-pair production in polarized positron-electron annihilation

A theoretical description of photon-pair production in polarized positron-electron annihilation is presented. Complete one-loop electroweak radiative corrections are calculated taking into account the exact dependence on the electron mass. Analytical results are derived with the help of the SANC system. The relevant contributions to the cross section are calculated analytically using the helicity amplitude approach. The cases of unpolarized and longitudinally polarized fermions in the initial state are investigated. Calculations are realized in the Monte Carlo integrator MCSANCee and generator ReneSANCe which allow one the implementation of any experimental cuts used in the analysis of ${e}^{+}{e}^{\ensuremath{-}}$ annihilation data of both low and high energies.

Electroweak corrections to Higgs boson production via W W fusion at the future LHeC

Precision measurement of quark Yukawa couplings is a crucial aspect of the Higgs property study. Proposed as a future upgrade of the Large Hadron Collider (LHC), the Large Hadron electron Collider (LHeC) provides opportunities to probe quark Yukawa couplings with a high precision because of relatively low QCD background as compared with that of the Higgs processes at the LHC. For this purpose, it is important to have a precision prediction of the Higgs production rate at the LHeC. The leading production channel of the Higgs boson at the LHeC is via weak boson fusion (WBF) which has the unique kinematic feature of forward tagging jets. As QCD corrections are suppressed by the simple color structure of the process, electroweak (EW) radiative corrections become particularly important. In this paper, we focus on the EW radiative corrections at next-to-leading order for the Higgs-boson production via charge current WBF processes at the LHeC. In the two renormalization schemes we use, the EW corrections are respectively at the level of 9% and 18% relative to the leading order result, for a center-of-mass energy at 1.98 TeV, and the next-to-leading order results in both schemes agree up to a truncation error expected from the perturbative method. The size of the EW corrections exceeds that from QCD radiations and is shown to be important for the study of Higgs phenomenology.

One-loop corrections for WW to HH in Higgs EFT with the electroweak chiral Lagrangian

In this work we present the computation of the one-loop electroweak radiative corrections to the scattering process $WW\to HH$ within the context of the Higgs Effective Field Theory (HEFT). We assume that the fermionic interactions are like in the Standard Model, whereas the Beyond Standard Model interactions in the bosonic sector are given by the Electroweak Chiral Lagrangian. The computation of the one-loop amplitude and the renormalization program is performed in terms of the involved one-particle-irreducible functions (1PI) and using $R_\xi$ covariant gauges. The renormalization of 1PI functions at arbitrary external momenta is a more ambitious program than just renormalizing the amplitude with on-shell external legs and it has the advantage that they can be used in several scattering amplitudes. In fact, we use here some of the 1PI functions already computed in our previous work (devoted to $WZ \to WZ$). We will complement them here with the computation of the new 1PI functions required for $WW \to HH$. From this renormalization procedure we will also derive the full set of renormalized coefficients of the EChL that are relevant for this scattering process. In the last part, we will present the numerical results for the EChL predictions of the one-loop level cross section, $\sigma(WW \to HH)|_{\rm 1-loop}$, as a function of the center of mass energy, showing the relative size of the one-loop radiative corrections respect to the tree level prediction in terms of the EChL coefficients. The results of the one-loop corrections to $WW \to HH$ for the SM case will be also presented, for comparison with the EChL case, following the same computational method, i.e., by means of the renormalization of 1PI functions.

NLO QCD and EW corrections to off-shell tZj production at the LHC

The production of a single top quark in association with a Z boson (tZj production) at the LHC is a relevant probe of the electroweak sector of the Standard Model as well as a window to possible new-physics effects. The growing experimental interest in performing differential measurements for this process demands an improved theoretical modelling in realistic fiducial regions. In this article we present an NLO-accurate tZj calculation that includes complete off-shell effects and spin correlations, combining QCD and electroweak radiative corrections to the LO signal. Integrated and differential cross sections are shown for a fiducial setup characterised by three charged leptons, two jets, and missing energy.

Effects of Electroweak Radiative Corrections in Polarized Low-Energy Electron–Positron Annihilation into Lepton Pairs

Complete one-loop electroweak radiative corrections to the cross section of the process {{e}^{ + }}{{e}^{ - }} to {{mu }^{ - }}{{mu }^{ + }}({{tau }^{ - }}{{tau }^{ + }}) are evaluated with the help of the SANC system. Higher-order contributions of the initial state radiation are computed in the QED structure function formalism. Numerical results are given for the center-of-mass energy range sqrt s = 5, 7 GeV for various polarization degrees of the initial particles. This study is a contribution to the research program of the Super Charm-Tau Factory project being under development in Sarov, Russia.

Full electroweak 𝒪(α) corrections to Higgs-boson production processes with beam polarization at the International Linear Collider

Abstract We present the full ${{\cal O}}(\alpha )$ electroweak radiative corrections to the production of nine Higgs bosons with beam polarization at the International Linear Collider (ILC). The computation is performed with the help of GRACE-Loop. We compare the full ${{\cal O}}(\alpha )$ electroweak radiative corrections with the factorized initial-state radiation (ISR) effects to estimate the pure weak corrections. This reveals that the pure weak corrections are not negligible and should be taken into account for precision measurements of the Higgs-boson property at the ILC experiments.

EW radiative corrections to theory predictions of charge asymmetry for W-boson hadroproduction

The higher-order predictions of the lepton charge asymmetry (the W-boson charge asymmetry ) for the leptonic final state of the W-boson hadroproduction in proton–proton (pp) collisions are presented. The predictions from the state-of-the-art computations are reported for achieving adequate description of the by including next-to-leading order (NLO) electroweak (EW) radiative corrections in combination with next-to-NLO (NNLO) quantum chromodynamics (QCD) radiative corrections. The combined predictions NNLO QCD+NLO EW and NNLO QCD × NLO EW, based on standard additive and factorised combination prescriptions in turn, are provided in the fiducial phase space of the pseudorapidity of the decay lepton (of the rapidity of the W-boson), comprising both central and forward detector acceptance regions as η l ≤ 4.5 (y W ≤ 4.5). The inclusion of the NLO EW effects for the () constitutes additional input for the relative u- and d-quark densities in the proton, which is also of high importance in the domain of the high-precision studies. The predicted distributions are compared with the actual measurements by CERN Large Hadron Collider (LHC) experiments at 8 TeV pp collisions energies. The combined predictions for the () distributions are also provided in comparisons with the NNLO QCD predictions at both 13 TeV and 14 TeV energies. The impact of the NLO EW corrections for the () distributions is extensively assessed by means of relative correction factor analysis with respect to the NNLO QCD predictions, in addition to a detailed K-factor analysis with respect to the leading order (LO) accuracy. The predicted results show that the NLO EW effects have larger impact in the forward η l region of the contrary to the central η l region, and is sizable in some of the y W ranges of the . The paper suggests inclusion of the presented EW corrections at NLO to have explicit accounting for the EW effects for the () in phenomenological studies.

One-Loop Electroweak Radiative Corrections to Polarized Møller Scattering

This work is devoted to a theoretical description of polarized Møller scattering. Complete one-loop electroweak radiative corrections are calculated in the helicity amplitude approach with allowance for the exact dependence on the muon mass. Numerical results are presented for integrated unpolarized and polarized cross sections as well as angular differential distributions. Calculations are performed using ReneSANCe Monte Carlo generator and MCSANC Monte Carlo integrator.

E + e − γ production at photon-photon colliders at complete electroweak NLO accuracy * *Supported in part by the National Natural Science Foundation of China (11775211, 12061141005) and the CAS Center for Excellence in Particle Physics (CCEPP)

We present the NLO electroweak radiative corrections to the production in γγ collision, which is an ideal channel for calibrating the beam luminosity of a Photon Linear Collider. We analyze the dependence of the total cross section on the beam colliding energy, and then investigate the kinematic distributions of final particles at various initial photon beam polarizations at EW NLO accuracy. The numerical results indicate that the EW relative corrections to the total cross section are non-negligible and become increasingly significant as the increase of the beam colliding energy, even can exceed –10% in the γγ collision at . Such EW corrections are very important and should be taken into consideration in precision theoretical and experimental studies at high-energy γγ colliders.

Electroweak effects in polarized muon-electron scattering

A theoretical description of elastic polarized muon-electron scattering is presented. Complete one-loop electroweak radiative corrections are calculated with taking into account the exact dependence on the muon mass. The effects due to some higher-order corrections and the electroweak scheme dependence are analyzed. The case of longitudinally polarized fermions in the initial state is investigated. Analytical results are derived with the help of the sanc system. Numerical results are presented for unpolarized and polarized cross sections. Calculations are realized in the Monte Carlo integrator mcsancee and generator renesance, which allow the implementation of any experimental cuts used in the analysis of elastic $\ensuremath{\mu}\ensuremath{-}e$ scattering data.

Update on |Vus| and |Vus/Vud| from semileptonic kaon and pion decays

We discuss the recent progress in the study of semileptonic kaon and pion decays, including new experimental results, improved electroweak radiative corrections, form factor calculations and isospin-breaking effects. As a result, we obtain $|V_{us}|=0.22309(40)(39)(3)$ from kaon semileptonic decays and $|V_{us}/V_{ud}|=0.22908(66)(41)(40)(2)(1)$ from the ratio between the kaon and pion semileptonic decay rates. We report an apparent violation of the top-row Cabibbo-Kobayashi-Maskawa matrix unitarity at a $3.2\sim 5.6\sigma$ level, and a discrepancy at a $2.2\sigma$ level between the value of $|V_{us}/V_{ud}|$ determined from the vector and axial charged weak interactions. Prospects for future improvements in those comparative precision tests involving $|V_{ud}|$, $|V_{us}|$ and their implications for physics beyond the Standard Model are described.

Improved Ke3 radiative corrections sharpen the K\u03bc2\u2013Kl3 discrepancy

The measurements of Vus in leptonic (Kμ2) and semileptonic (Kl3) kaon decays exhibit a 3σ disagreement, which could originate either from physics beyond the Standard Model or some large unidentified Standard Model systematic effects. Clarifying this issue requires a careful examination of all existing Standard Model inputs. Making use of a newly-proposed computational framework and the most recent lattice QCD results, we perform a comprehensive re-analysis of the electroweak radiative corrections to the Ke3 decay rates that achieves an unprecedented level of precision of 10−4, which improves the current best results by almost an order of magnitude. No large systematic effects are found, which suggests that the electroweak radiative corrections should be removed from the “list of culprits” responsible for the Kμ2–Kl3 discrepancy.

Radiative Corrections to Semileptonic Beta Decays: Progress and Challenges

We review some recent progress in the theory of electroweak radiative corrections in semileptonic decay processes. The resurrection of the so-called Sirlin’s representation based on current algebra relations permits a clear separation between the perturbatively-calculable and incalculable pieces in the O(GFα) radiative corrections. The latter are expressed as compact hadronic matrix elements that allow systematic non-perturbative analysis such as dispersion relation and lattice QCD. This brings substantial improvements to the precision of the electroweak radiative corrections in semileptonic decays of pion, kaon, free neutron and JP=0+ nuclei that are important theory inputs in precision tests of the Standard Model. Unresolved issues and future prospects are discussed.