One-loop Electroweak Corrections Research Articles

H-COUP Version 3: A program for one-loop corrected decays of any Higgs bosons in non-minimal Higgs models

The H-COUP program is provided as a package of Fortran codes, which can compute observables related to Higgs bosons including radiative corrections in various extended Higgs sectors. We give a manual for the latest version of H-COUP (H-COUP_3.0), in which decay rates and branching ratios of all the Higgs bosons can be calculated at one-loop level in EW and Higgs interactions with QCD corrections in the Higgs singlet model, four types of the two Higgs doublet model with a softly-broken Z2 symmetry, and the inert doublet model. The previous version (H-COUP_2.0) can evaluate those only for the standard model like Higgs boson with the mass of 125 GeV (h). In H-COUP_3.0, renormalized quantities are computed based on the gauge-independent on-shell renormalization scheme. The source code of H-COUP_3.0 can be downloaded via the following link: http://www-het.phys.sci.osaka-u.ac.jp/~hcoup. By using H-COUP_3.0, we can compare the precise measurements of the properties of h and direct searches for additional Higgs bosons with their predictions at one-loop level, by which we can reconstruct the structure of the Higgs sector. New version program summaryProgram Title: H-COUP Version 3 5CPC Library link to program files:https://doi.org/10.17632/f88szmrj5x.3Developer's repository link:http://www-het.phys.sci.osaka-u.ac.jp/~hcoupLicensing provisions: GPLv3Programming language: Fortran90Journal reference of previous version: Comput. Phys. Commum. 257 (2020) 107512Does the new version supersede the previous version?: YesReasons for the new version: The previous version (H-COUP version 2) is a package of Fortran codes to provide one-loop corrected couplings, decay rates and branching ratios of the 125 GeV Higgs boson in the Higgs Singlet Model (HSM), the Two Higgs doublet models (THDMs) with a softly-broken Z2 symmetry, and the Inert Doublet Model (IDM). In the new version (H-COUP version 3), the H-COUP program has been improved to calculate the decay rates and the branching ratios of all the Higgs bosons including one-loop corrections in the above models. These calculations are performed based on the gauge independent on-shell renormalization scheme.Summary of revisions: We have added radiatively corrected decay rates and branching ratios for all the additional Higgs bosons, not only for the 125 GeV Higgs boson, in the extended Higgs models. Furthermore, several choices are provided for renormalization schemes used to evaluate electroweak corrections. The scalar two-point functions are renormalized by on-shell scheme as in the previous version, while the renormalization for the tadpole is performed by either the standard tadpole scheme or the alternative tadpole scheme. The users can choose these renormalization schemes.Nature of problem: Decay rates and branching ratios of all the Higgs bosons can be calculated with one-loop electroweak corrections and QCD corrections in the HSM, four types of the THDMs with the softly-broken Z2 symmetry, and the IDM. In the calculations of additional Higgs boson decays, for the three-body decay processes and loop induce processes of additional Higgs bosons, electroweak corrections are not included. As for the QCD correction, next-to-leading order or next-to-next-to-leading order corrections are included, depending on the decay process.Solution method: Electroweak corrections are evaluated based on the gauge independent on-shell renormalization scheme, while some parameters are renormalized by the MS‾ scheme. QCD corrections are evaluated with the MS‾ scheme.Additional comments including restrictions and unusual features: All functions up to the previous version are included in H-COUP version 3.

Electroweak loop contributions to the direct detection of wino dark matter

Electroweak loop corrections to the matrix elements for the spin-independent scattering of cold dark matter particles on nuclei are generally small, typically below the uncertainty in the local density of cold dark matter. However, as shown in this paper, there are instances in which the electroweak loop corrections are relatively large, and change significantly the spin-independent dark matter scattering rate. An important example occurs when the dark matter particle is a wino, e.g., in anomaly-mediated supersymmetry breaking (AMSB) and pure gravity mediation (PGM) models. We find that the one-loop electroweak corrections to the spin-independent wino LSP scattering cross section generally interfere constructively with the tree-level contribution for AMSB models with negative Higgsino mixing, mu < 0, and in PGM-like models for both signs of mu , lifting the cross section out of the neutrino fog and into a range that is potentially detectable in the next generation of direct searches for cold dark matter scattering.

The Effects of the Widths on the One-Loop Electroweak Corrections to the pp ⟶ W W Process

In this paper, we study the effects of the widths of unstable particles on the one-loop electroweak corrections for the pp ⟶ WW process at the TeV scale within the framework of the complex mass scheme. We also investigate, for this same process, the unitarity of the theory at high energies.

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.

ReneSANCe event generator for high-precision e + e − physics

We present a new version of the Monte Carlo event generator ReneSANCe. The generator takes into account complete one-loop electroweak (EW) corrections, higher order QED corrections in the leading logarithm (LL) approximation and some higher order EW corrections to processes at e + e − colliders with finite particle masses and arbitrary polarizations of initial and final particles. ReneSANCe can produce events in the full phase space and this option is available for a wide range of center-of-mass energies.

Hadron-hadron collision mode in ReneSANCe-v1.3.0

We report an implementation of the hadron-hadron (pp and pp¯) collision mode to the Monte Carlo event generator ReneSANCe — the code that was previously developed for e+e− collisions. The described extension of ReneSANCe currently contains neutral and charged current Drell-Yan processes pp[pp¯]→ZX→ℓ+ℓ−X, pp[pp¯]→W+X→ℓ+νℓX and pp[pp¯]→W−X→ℓ−ν¯ℓX. We take into account complete one-loop electroweak (EW) and one-loop QCD corrections to these processes. The calculation is based on the SANC (Support for Analytic and Numeric Calculations for experiments at colliders) modules. The generator is constructed in such a way that new processes can be easily added. The paper contains a theoretical description of the SANC approach, numerical validations and a manual. Program summaryProgram Title:ReneSANCe version 1.3.0CPC Library link to program files:https://doi.org/10.17632/wp36f7t3ft.2Licensing provisions: GPLv3Programming language: FORTRAN 77/90, C, C++External routines: ROOT (https://root.cern.ch), LHAPDF (https://lhapdf.hepforge.org)Journal reference of previous version: Comput. Phys. Commun. 256 (2020) 107445Does the new version supersede the previous version?: Yes.Reasons for the new version: Implementation of the hadron-hadron collision mode.Summary of revisions: Added support of the pp and pp¯ collision modes. Implemented neutral and charged current Drell-Yan processes.Nature of problem: Theoretical calculations at next-to-leading order in perturbation theory allow to compute higher precision amplitudes for Standard Model processes and decays. Proper treatments of UV divergences and IR singularities are performed.Solution method: Numerical integration of the precomputed differential expressions for cross sections of certain processes implemented as SANC modules [1,2].Additional comments including restrictions and unusual features:ReneSANCe homepage https://renesance.hepforge.org. The SANC modules and codes also available at http://sanc.jinr.ru. The list of processes in the hadron-hadron collision mode is limited to pp[pp¯]→ZX→ℓ+ℓ−X, pp[p¯]→W+X→ℓ+νℓX and pp[p¯]→W−X→ℓ+ν¯ℓX.

One-loop corrections to the Higgs boson invisible decay in a complex singlet extension of the SM

The search for dark matter (DM) at colliders is founded on the idea of looking for something invisible. There are searches based on production and decay processes where DM may reveal itself as missing energy. If nothing is found, our best tool to constrain the parameter space of many extensions of the Standard Model (SM) with a DM candidate is the Higgs boson. As the measurements of the Higgs couplings become increasingly precise, higher-order corrections will start to play a major role. The tree-level contribution to the invisible decay width provides information about the portal coupling. Higher-order corrections also give us access to other parameters from the dark sector of the Higgs potential that are not present in the tree-level amplitude. In this work we will focus on the complex singlet extension of the SM in the phase with a DM candidate. We calculate the one-loop electroweak corrections to the decay of the Higgs boson into two DM particles. We find that the corrections are stable and of the order of a few percent. The present measurement of the Higgs invisible branching ratio, $\mathrm{BR}(H\ensuremath{\rightarrow}\text{ }\mathrm{invisible})&lt;0.11$, already constrains the parameter space of the model at leading order. We expect that by the end of the LHC the experimental measurement will require the inclusion of the electroweak corrections to the decay in order to match the experimental accuracy. Furthermore, the only competing process, which is direct detection, is shown to have a cross section below the neutrino floor.

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.

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.

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.

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.

Relic density of dark matter in the inert doublet model beyond leading order for the low mass region. II. Coannihilation

We examine the relic density of the light mass dark matter region in the inert doublet model (IDM) when the dominant process is due to co-annihilation between the lightest neutral scalars of the model. The full one-loop electroweak corrections are computed in an on-shell scheme and are found to be well approximated as an effective cross-section expressed in terms of $Z$-observables. The electroweak corrections to the subdominant process which consists of an annihilation into an on-shell $W$ and an off-shell $W$, that is calculated as a annihilation into a 3-body final state, is also performed. The latter reveals an important dependence on a parameter that describes the self-interaction of the new scalars (solely within the dark sector), a parameter which is not accessible in tree-level calculations of standard model (SM)-IDM interactions.

Relic density of dark matter in the inert doublet model beyond leading order for the low mass region. IV. The Higgs resonance region

One-loop electroweak corrections to the annihilation cross-sections of dark matter in the Higgs resonance region of the inert doublet model (IDM) are investigated. The procedure of how to implement the width of the Higgs in order to regularise the amplitude both at tree-level and at one-loop together with the renormalisation of a key parameter of the model, are thoroughly scrutinised. The discussions go beyond the application to the relic density calculation and also beyond the IDM so that addressing these technical issues can help in a wider context. We look in particular at the dominant channels with the $b \bar b$ final state and the more involved 3-body final state, $W f \bar f^\prime$, where both a resonance and an anti-resonance, due to interference effects, are present. We also discuss how to integrate over such configurations when converting the cross-sections into a calculation of the relic density.

Relic density of dark matter in the inert doublet model beyond leading order for the low mass region. III. Annihilation to three-body final states

We perform the first one-loop electroweak corrections for $2 \to 3$ processes for dark matter annihilation. These are the dominant processes that enter the computation of the relic density for the low mass region of the inert doublet model (IDM) when annihilations to two on-shell vector bosons are closed. The impact of the one-loop corrections are important as they involve, through rescattering effects, not only a dependence on the parameter controlling the dark sector, not present if a calculation at tree-level is conducted, but also on the renormalisation scale. These combined effects should be taken into account in analyses based on tree-level cross-sections of the relic density calculations, as a theoretical uncertainty which we find to be much larger than the cursory $\pm 10\%$ uncertainty that is routinely assumed, independently of the model parameters.

Electroweak Effects in e+e−→ZH Process

Electroweak radiative corrections to the cross-section of the process e+e−→ZH are considered. The complete one-loop electroweak radiative corrections 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 produced by a new version of the ReneSANCe event generator and MCSANCee integrator for the conditions of future electron-positron colliders. The resulting theoretical uncertainty in the description of this process is estimated.

One-loop electroweak radiative corrections to charged lepton pair production in photon-photon collisions

We provide high-precision predictions for muon-pair and tau-pair productions in a photon-photon collision by considering a complete set of one-loop-level scattering amplitudes, i.e., electroweak (EW) corrections together with soft and hard QED radiation. Accordingly, we present a detailed numerical discussion with particular emphasis on the pure QED corrections as well as genuinely weak corrections. The effects of angular and initial beam polarization distributions on production rates are also discussed. An improvement is observed by a factor of two with oppositely polarized photons. Our results indicate that the one-loop EW radiative corrections enhance the Born cross section and the total relative correction is typically about 10% for both production channels. It appears that the full EW corrections to $\ensuremath{\gamma}\ensuremath{\gamma}\ensuremath{\rightarrow}{\ensuremath{\ell}}^{\ensuremath{-}}{\ensuremath{\ell}}^{+}$ are required to match a percent level accuracy.

Precise predictions for charged Higgs boson pair production in photon-photon collisions

The charged Higgs pair production via photon-photon collisions is investigated in the framework of two Higgs doublet model (2HDM), taking into account a full set of one-loop-level scattering amplitudes, i.e., including electroweak (EW) corrections together with soft and hard QED radiation. The numerical evaluation is carried out for three different scenarios, so-called non-alignment, low-mH and short-cascade, defined in the presence of the up-to-date experimental constraints and consistent with theoretical constraints as well. The total cross sections of γγ→H−H+ are scanned over the plane (mϕ0,s), where ϕ0 is h0 for low-mH0 scenario and H0 for other two scenarios. The regions of the parameter space in which the production rates are sufficiently large are highlighted for each scenario. The production rates in different polarization collision modes of initial beams are also discussed. It can be enhanced up to two-times by oppositely polarized photons at high energies and right-handed polarized photons at low energies. Furthermore, decay channels of the charged Higgs boson are examined for each scenario. It is observed that the one-loop EW corrections, i.e., the virtual plus real radiation corrections, reduce the tree-level cross sections and the relative correction is typically in the range of −10% to −30%, depending on model parameters.

One-loop electroweak radiative corrections to lepton pair production in polarized electron-positron collisions

This paper presents the high-precision theoretical predictions for $e^+e^- \to l^-l^+$ scattering. Calculations are performed using the {\tt SANC} system. They take into account complete one-loop electroweak radiative corrections as well as longitudinal polarization of initial beams. Reaction observables are obtained using the helicity amplitude method with taking into account initial and final state fermion masses. Numerical results are given for the center-of-mass energy range $\sqrt{s}=250-1000$ GeV with various degrees of polarization.

On the effective theory of neutrino-electron and neutrino-quark interactions

We determine the four-fermion effective theory of neutrino interactions within the Standard Model including one-loop electroweak radiative corrections, in combination with the measured muon lifetime and precision electroweak data. Including two-loop matching and three-loop running corrections, we determine lepton coefficients accounting for all large logarithms through relative order O(ααs) and quark coefficients accounting for all large logarithms through O(α). We present four-fermion coefficients valid in nf=3 and nf=4 flavor quark theories, as well as in the extreme low-energy limit. We relate the coefficients in this limit to neutrino charge radii governing matter effects via forward neutrino scattering on charged particles.

MCSANCee generator with one-loop electroweak corrections for processes with polarized e+e- beams

A new Monte Carlo event generator MCSANCee for simulations of processes at future e+e− colliders is presented. Complete one-loop electroweak radiative corrections and polarization of the initial beams are taken into account. The present generator includes the following processes: . Numerical results for the process are shown. Plans for the further extension of the MCSANCee generator are discussed.