Title: Mixed EW-QCD leading fermionic three-loop corrections at $$ \mathcal{O} $$(αsα2) to electroweak precision observables
A bstract Measurements of electroweak precision observables at future electron-position colliders, such as the CEPC, FCC-ee, and ILC, will be sensitive to physics at multi-TeV scales. To achieve this sensitivity, precise predictions for the Standard Model expectations of these observables are needed, including corrections at the three- and four-loop level. In this article, results are presented for the calculation of a subset of three-loop mixed electroweak-QCD corrections, stemming from diagrams with a gluon exchange and two closed fermion loops. The numerical impact of these corrections is illustrated for a number of applications: the prediction of the W-boson mass from the Fermi constant, the effective weak mixing angle, and the partial and total widths of the Z boson. Two alternative renormalization schemes for the top-quark mass are considered, on-shell and $$ \overline{\mathrm{MS}} $$ MS ¯ . more »« less
Dubovyk, Ievgen; Freitas, Ayres; Gluza, Janusz; Grzanka, Krzysztof; Riemann, Tord; Usovitsch, Johann
(, 40th International Conference on High Energy Physics (ICHEP2020))
null
(Ed.)
Phenomenologically relevant electroweak precision pseudo-observables related to Z-boson physics are discussed in the context of the strong experimental demands of future e+e− colliders. The recent completion of two-loop Z-boson results is summarized and a prospect for the 3-loop Standard Model calculation of the Z-boson decay pseudo-observable is given.
In this proceeding, we highlight the computation of leading fermionic three-loop corrections to electroweak precision observables (EWPOs) accomplished recently. We summarize the numerical analysis and provide an outlook.
Belyaev, Alexander; Chivukula, R Sekhar; Fuks, Benjamin; Simmons, Elizabeth H; Wang, Xing
(, Physical Review D)
Vectorial partners of the Standard Model quarks and leptons are predicted in many dynamical models of electroweak symmetry breaking. The most easily accessible of these new particles, either due to mass or couplings, are typically expected to be the partners of the third-generation fermions. It is therefore essential to explore the signatures of these particles at future high-energy colliders. We study the potential of a high- energy muon collider to singly produce a vectorlike top-quark partner via an electroweak dipole moment operator, such an operator being typical of composite constructions beyond the Standard Model. We use a phenomenological model for third-generation quarks and their partners that satisfies an extended custodial symmetry. This automatically protects the W-boson and Z-boson masses from receiving large electroweak corrections, and it allows the model to be viable given current electroweak data. We demonstrate that cross sections associated with dipole-induced vectorlike quark production can easily exceed those inherent to more conventional single-production modes via ordinary electroweak couplings. We then explore the associated phenomenology, and we show that at least one (and often more than one) of the extra vectorlike states can be studied at high-energy muon colliders. Typical accessible masses are found to range up to close to the kinematic production threshold, when the vectorlike partners are produced in combination with an ordinary top quark.
Song, Qian; Freitas, Ayres
(, Journal of High Energy Physics)
null
(Ed.)
A bstract Precision studies of the Higgs boson at future e + e − colliders can help to shed light on fundamental questions related to electroweak symmetry breaking, baryogenesis, the hierarchy problem, and dark matter. The main production process, e + e − → HZ , will need to be controlled with sub-percent precision, which requires the inclusion of next-to-next-to-leading order (NNLO) electroweak corrections. The most challenging class of diagrams are planar and non-planar double-box topologies with multiple massive propagators in the loops. This article proposes a technique for computing these diagrams numerically, by transforming one of the sub-loops through the use of Feynman parameters and a dispersion relation, while standard one-loop formulae can be used for the other sub-loop. This approach can be extended to deal with tensor integrals. The resulting numerical integrals can be evaluated in minutes on a single CPU core, to achieve about 0.1% relative precision.
Gehrmann-De_Ridder, Aude; Preuss, Christian T; Williams, Ciaran
(, Journal of High Energy Physics)
A<sc>bstract</sc> We present next-to-leading order perturbative QCD predictions for four-jet-like event-shape observables in hadronic Higgs decays. To this end, we take into account two Higgs-decay categories: involving either the Yukawa-induced decay to a$${\text{b}}\overline{{\text{b}} }$$pair or the loop-induced decay to two gluons via an effective Higgs-gluon-gluon coupling. We present results for distributions related to the event-shape variables thrust minor, light-hemisphere mass, narrow jet broadening,D-parameter, and Durham four-to-three-jet transition variable. For each of these observables we study the impact of higher-order corrections and compare their size and shape in the two Higgs-decay categories. We find large NLO corrections with a visible shape difference between the two decay modes, leading to a significant shift of the peak in distributions related to the H→gg decay mode.
Chen, Lisong, and Freitas, Ayres. Mixed EW-QCD leading fermionic three-loop corrections at $$ \mathcal{O} $$(αsα2) to electroweak precision observables. Retrieved from https://par.nsf.gov/biblio/10283700. Journal of High Energy Physics 2021.3 Web. doi:10.1007/JHEP03(2021)215.
Chen, Lisong, & Freitas, Ayres. Mixed EW-QCD leading fermionic three-loop corrections at $$ \mathcal{O} $$(αsα2) to electroweak precision observables. Journal of High Energy Physics, 2021 (3). Retrieved from https://par.nsf.gov/biblio/10283700. https://doi.org/10.1007/JHEP03(2021)215
Chen, Lisong, and Freitas, Ayres.
"Mixed EW-QCD leading fermionic three-loop corrections at $$ \mathcal{O} $$(αsα2) to electroweak precision observables". Journal of High Energy Physics 2021 (3). Country unknown/Code not available. https://doi.org/10.1007/JHEP03(2021)215.https://par.nsf.gov/biblio/10283700.
@article{osti_10283700,
place = {Country unknown/Code not available},
title = {Mixed EW-QCD leading fermionic three-loop corrections at $$ \mathcal{O} $$(αsα2) to electroweak precision observables},
url = {https://par.nsf.gov/biblio/10283700},
DOI = {10.1007/JHEP03(2021)215},
abstractNote = {A bstract Measurements of electroweak precision observables at future electron-position colliders, such as the CEPC, FCC-ee, and ILC, will be sensitive to physics at multi-TeV scales. To achieve this sensitivity, precise predictions for the Standard Model expectations of these observables are needed, including corrections at the three- and four-loop level. In this article, results are presented for the calculation of a subset of three-loop mixed electroweak-QCD corrections, stemming from diagrams with a gluon exchange and two closed fermion loops. The numerical impact of these corrections is illustrated for a number of applications: the prediction of the W-boson mass from the Fermi constant, the effective weak mixing angle, and the partial and total widths of the Z boson. Two alternative renormalization schemes for the top-quark mass are considered, on-shell and $$ \overline{\mathrm{MS}} $$ MS ¯ .},
journal = {Journal of High Energy Physics},
volume = {2021},
number = {3},
author = {Chen, Lisong and Freitas, Ayres},
editor = {null}
}
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