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1. Mixed EW-QCD leading fermionic three-loop corrections at $$ \mathcal{O} $$(αsα2) to electroweak precision observables

   https://doi.org/10.1007/JHEP03(2021)215  

   Chen, Lisong; Freitas, Ayres (March 2021, Journal of High Energy Physics)

   null (Ed.)

   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 ¯ . 

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2. Progress in top-quark pair production cross section calculations and impact on parton distribution functions of the proton

   https://doi.org/10.22323/1.478.0332  

   Guzzi, Marco; Ablat, Alim; Dulat, Sayipjamal; Hou, T-J; Kidonakis, Nikolaos; Sitiwaldi, Ibrahim; Tonero, Alberto; Xie, Keping; Yuan, C-P (January 2025, Sissa Medialab)

   We discuss the impact of eligible top-quark pair production differential cross-section measurements at the LHC with a collision energy of 13 TeV on the parton distribution functions (PDFs) of the proton as well as the impact of approximate next-to-next-to-next-to-leading order (aN3LO) QCD corrections combined with next-to-leading order (NLO) electroweak (EW) corrections on tt¯ observables. We illustrate the effects on the gluon PDF at large x from an optimal baseline selection of data in NNLO global fits, and show comparisons between the theory prediction for tt¯ total and differential cross sections at aN3LO QCD combined with NLO EW and recent measurements from the ATLAS and CMS collaborations at the LHC. 

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3. Search for a vector-like quark T′ → tH via the diphoton decay mode of the Higgs boson in proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV

   https://doi.org/10.1007/JHEP09(2023)057  

   Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Dragicevic, M.; Escalante Del Valle, A.; Hussain, P. S.; Jeitler, M.; et al (September 2023, Journal of High Energy Physics)

   A bstract A search for the electroweak production of a vector-like quark T′, decaying to a top quark and a Higgs boson is presented. The search is based on a sample of proton-proton collision events recorded at the LHC at $$ \sqrt{s} $$ s = 13 TeV, corresponding to an integrated luminosity of 138 fb − 1 . This is the first T′ search that exploits the Higgs boson decay to a pair of photons. For narrow isospin singlet T′ states with masses up to 1.1 TeV, the excellent diphoton invariant mass resolution of 1–2% results in an increased sensitivity compared to previous searches based on the same production mechanism. The electroweak production of a T′ quark with mass up to 960 GeV is excluded at 95% confidence level, assuming a coupling strength κ T = 0 . 25 and a relative decay width Γ /M T′ < 5%. 

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4. Measurement of the top quark antiquark charge asymmetry in highly boosted events in the single-lepton channel at 13 TeV

   Gerber, Cecilia; Becerril Gonzalez, Hugo; Roy, Titas; Chen, Xuan (May 2022, CMS-PAS-TOP-21-014)

   The measurement of the charge asymmetry for highly boosted top quark pairs decaying to a single lepton and jets is presented. The analysis is performed using 138 fb−1 of data collected in pp collisions at s√=13 TeV with the CMS detector during Run 2 of the Large Hadron Collider. The selection is optimized for top quark-antiquark pairs produced with large Lorentz boosts, resulting in non-isolated leptons and overlapping jets. The top quark charge asymmetry is measured for events with tt⎯⎯ invariant mass larger than 750 GeV and corrected for detector and acceptance effects using a binned maximum likelihood fit. The measured top quark charge asymmetry is in good agreement with the standard model prediction at next-to-next-to-leading order in perturbation theory with next-to-leading order electroweak corrections. Differential distributions for two invariant mass ranges are also presented. 

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5. Hadronic effects in Møller scattering at NNLO

   https://doi.org/10.1007/JHEP08(2022)183  

   Erler, Jens; Ferro-Hernández, Rodolfo; Freitas, Ayres (August 2022, Journal of High Energy Physics)

   A bstract Two-loop electroweak corrections to polarized Møller scattering are studied in two different schemes at low energies. We find the finite Q 2 corrections to be well under control. The hadronic and perturbative QCD corrections to the γZ two-point function are incorporated through the weak mixing angle at low energies, which introduce an error of 0 . 08 × 10 − 3 in the weak charge of the electron $$ {Q}_W^e $$ Q W e . Furthermore, by studying the scheme dependence, we obtain an estimate of the current perturbative electroweak uncertainty, $$ \delta {Q}_W^e $$ δ Q W e ≈ 0 . 23 × 10 − 3 , which is five times smaller than the precision estimated for the MOLLER experiment ( $$ \delta {Q}_W^e $$ δ Q W e = 1 . 1 × 10 − 3 ). Future work is possible to reduce the theory error further. 

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