Articles de revues : « Electroweak fit »

1

Ciuchini, M., E. Franco, S. Mishima et L. Silvestrini. « Electroweak theory and global fit ». EPJ Web of Conferences 60 (2013) : 08004. http://dx.doi.org/10.1051/epjconf/20136008004.

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Quast, Günter. « Global fit to electroweak precision data ». European Physical Journal C 33, S1 (3 février 2004) : s641—s643. http://dx.doi.org/10.1140/epjcd/s2004-03-1611-4.

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Zhang, Ying, Shao-Zhou Jiang et Qing Wang. « Global Electroweak Fit and Its Implication for Z ′ ». Communications in Theoretical Physics 61, n^o 6 (juin 2014) : 729–34. http://dx.doi.org/10.1088/0253-6102/61/6/11.

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Gurtu, Atul. « Precision Tests of the Electroweak Theory ». International Journal of Modern Physics A 18, n^o 21 (20 août 2003) : 3591–627. http://dx.doi.org/10.1142/s0217751x03013958.

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Electroweak data from the high energy electron–positron and proton–antiproton colliders are reviewed. On the whole the data is consistent with and supports the predictions of the electroweak theory. However, a crucial prediction of the theory remains to be verified: the existence of the Higgs boson and its light mass, less than 193 GeV, obtained from a fit to all the data within the electroweak framework. The lower limit on its mass from direct searches being 114 GeV, the mass of the Higgs is fixed within a narrow range which is expected to be explored at the Fermilab Tevatron experiments or later at the Large Hadron Collider at CERN.

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Kvedaraitė, Sandra. « Two-loop Electroweak Corrections to ϵ_K ». Journal of Physics : Conference Series 2446, n^o 1 (1 février 2023) : 012020. http://dx.doi.org/10.1088/1742-6596/2446/1/012020.

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Abstract The parameter εK measures CP violation in the neutral kaon system. It is a sensitive probe of new physics and plays a prominent role in the global fit of the Cabibbo-Kobabyashi-Maskawa matrix. As one of the first discovered sources of CP violation, it has been measured in experiment to permil precision. A simple reparametrization of the efFective Hamiltonian has been recently shown to drastically reduce the perturbative errors coming from the charm-quark corrections, making the electroweak corrections relevant. In this proceedings, I will present the two-loop electroweak corrections to ϵK .

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HIOKI, ZENRŌ. « TOP AND HIGGS HUNTING VIA Mw AND Γz ». Modern Physics Letters A 06, n^o 23 (30 juillet 1991) : 2129–35. http://dx.doi.org/10.1142/s0217732391002311.

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Virtual top and Higgs effects are studied through the electroweak radiative corrections to the W boson mass, MW, and the total decay-width of the Z boson, ΓZ, by using the data [Formula: see text], [Formula: see text] and [Formula: see text]. Carrying out the χ2 fit in the framework of the standard electroweak theory, constraints are derived on the top-quark mass, mt, and the Higgs–boson mass, mϕ, which are almost free from the complicated hadron physics like parton model calculations. For example, [Formula: see text] for mϕ = 100 GeV (at 1σ level) while mϕ ≲ 680 GeV if mt ≤ 110 GeV and mϕ ≳ 280 GeV if mt ≥ 190 GeV . It is also studied how precise measurements of MW at LEP II improve these constraints.

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CHO, GI-CHOL. « LOOKING FOR Z′ BOSONS IN SUPERSYMMETRIC E6 Models THROUGH ELECTROWEAK PRECISION DATA ». Modern Physics Letters A 15, n^o 05 (20 février 2000) : 311–31. http://dx.doi.org/10.1142/s021773230000030x.

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We review constraints on additional Z′ bosons predicted in supersymmetric (SUSY) E6 models from electroweak experiments — Z-pole experiments, mW measurements and the low-energy neutral current (LENC) experiments. Four representative models — χ, ψ, η and ν — are studied in some detail. We find that the improved data of parity violation in cesium atom, which is 2.2-σ away from the standard model (SM) prediction, could be explained by the exchange of the heavy mass eigenstate Z2 in the intermediate state. The improvement over the SM can be found in χ, η, ν models, where the total χ2 of the fit to the 26 data points decreases by about five units, owing to the better fit to the atomic parity violation. Impacts of the kinetic mixing between the U (1)Y and U (1)′ gauge bosons on the χ2-analysis are studied. We find that the Z′ model with (βE,δ)=(-π/4,0.2), where βE is the mixing angle between Zχ and Zψ bosons and δ denotes the kinetic mixing, shows the most excellent fit to the data: The total χ2 decreases by about seven units as compared to the SM. We introduce the effective mixing parameter ζ, a combination of the mass and the kinetic mixing parameters. The 95% CL lower mass bound of Z2 can be shown as a function of ζ. A theoretical prediction on ζ and the U (1)′ gauge coupling gE is studied for the χ, ψ, η and ν models by assuming the minimal particle content of the SUSY E6 models.

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ELLIS, JOHN. « SUMMARY OF ICHEP 2004 ». International Journal of Modern Physics A 20, n^o 22 (10 septembre 2005) : 5297–315. http://dx.doi.org/10.1142/s0217751x05028806.

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Aspects of ICHEP 2004 are summarized from a theoretical point of view. QCD works, new NNLO calculations are becoming available and new string calculational tools are emerging, but no conclusions can yet be drawn about the discovery of the quark-gluon plasma or pentaquarks. The small upward shift in the experimental value of mt raises somewhat the central value of the Higgs mass extracted from a global electroweak fit, and the CKM model describes well the data from the B factories. The Super-Kamiokande, KamLAND and K2K experiments have evidence for oscillation dips in their neutrino data. Little Higgs models are interesting alternatives to low-energy supersymmetry for stabilizing the electroweak scale. Convincing experimental evidence for dark matter particles is still lacking. The LHC is on its way, the technology choice clarifies the roadmap for the ILC, and a multi-TeV CLIC would also have rich physics agenda.

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KONG, DERRICK. « NEW R VALUES FROM 2-5 GEV FROM THE BESII AT BEPC ». International Journal of Modern Physics A 16, supp01a (octobre 2001) : 281–83. http://dx.doi.org/10.1142/s0217751x01006693.

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We report preliminary R values for all 85 energy points scanned in the energy region of 2-5 GeV with the upgraded Beijing Spectrometer (BESII) at the Beijing Electron Positron Collider (BEPC). The typical uncertainties on the R values we measured are ~ 7%. The new R values have a significant impact on the predicted mass of the Higgs (mH) coming from the global fit to the electroweak data, and will also contribute to the interpretation of the E821 g - 2 experiment.

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Flächer, H., M. Goebel, J. Haller, A. Hoecker, K. Mönig et J. Stelzer. « Revisiting the global electroweak fit of the Standard Model and beyond with Gfitter ». European Physical Journal C 60, n^o 4 (19 mars 2009) : 543–83. http://dx.doi.org/10.1140/epjc/s10052-009-0966-6.

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Raby, Stuart. « Neutrino Masses and SO(10) SUSY GUTs ». International Journal of Modern Physics A 16, supp01b (septembre 2001) : 569–75. http://dx.doi.org/10.1142/s0217751x01007510.

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In this talk I discuss the qualitative features of an SO(10) SUSY GUT with an SU (2)× U (1) n family symmetry. I then describe the global fit of this theory to precision electroweak data [including charged fermion masses and mixing angles]. Finally, the predictions of the model for neutrino masses and mixing are discussed. The most predictive version of the model naturally fits atmospheric neutrino data with maximal νμ→ντ oscillations and solar neutrino data with small mixing angle MSW νe→νsterile oscillations.

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Rajec, Filip, Wei Su, Martin White et Anthony G. Williams. « Exploring the 2HDM with Global Fits in GAMBIT ». EPJ Web of Conferences 245 (2020) : 06022. http://dx.doi.org/10.1051/epjconf/202024506022.

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In this work, we present preliminary results of a global fit of the typeII two-Higgs-doublet model (2HDM) with the tool GAMBIT. Our study includes various constraints, including the theoretical constraints (unitarity, perturbativity and vacuum stability), Higgs searches at colliders, electroweak physics and flavour constraints. With the latest experimental results, our results not only confirm past studies but also go further in probing the model. We find, for example, that the measurements of B→K*µ+µ− angular observables cannot be explained in the type-II 2HDM.

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Liu, Guo-Li, et Ping Zhou. « The Contribution of Charged Bosons with Right-Handed Neutrinos to the Muon ${g-2}$ Anomaly in the Twin Higgs Models ». Universe 8, n^o 12 (11 décembre 2022) : 654. http://dx.doi.org/10.3390/universe8120654.

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We examine the charged boson and right-handed neutrino contribution to the muon g−2 anomaly in twin Higgs models with joint constraints of Higgs global fit data, precision electroweak data, leptonic flavor-changing decay μ→eγ, and the mass requirement of heavy-gauge bosons. It comes with the conclusion that some parameters, such as the coupling of charged Higgs to the lepton yμ, the top Yukawa yt, and heavy-gauge boson coupling to the lepton Vμ are constrained roughly in the range of 0.12≲yμ≲0.4, 0.4≲yt≲0.9, and 0.47≲Vμ≲1, respectively.

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COQUEREAUX, R., G. ESPOSITO FARÈSE et F. SCHECK. « NONCOMMUTATIVE GEOMETRY AND GRADED ALGEBRAS IN ELECTROWEAK INTERACTIONS ». International Journal of Modern Physics A 07, n^o 26 (20 octobre 1992) : 6555–93. http://dx.doi.org/10.1142/s0217751x9200301x.

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The Standard Model of Electroweak Interactions can be described by a generalized Yang-Mills field incorporating both the usual gauge bosons and the Higgs fields. The graded derivative by means of which the Yang-Mills field strength is constructed involves both a differential acting on space-time and a differential acting on an associative graded algebra of matrices. The square of the curvature for the corresponding covariant derivative yields the bosonic Lagrangian of the Standard Model. We show how to recover the whole fermionic part of the Standard Model in this framework. Quarks and leptons fit naturally into the smallest typical and nontypical irreducible representations of the graded algebra Lie SU(2|1) associated with the above associative ℤ2-graded algebra. The existence of reducible indecomposable representations leads naturally to flavor mixing in the quark sector, possibility of existence for a right neutrino and possible mixing in the leptonic sector. We therefore bridge the gap between noncommutative geometry and graded Lie algebras. The Z2 grading refers to left and right chiralities in the fermionic sector and to even and odd forms in the bosonic sector. Supergauge transformations could only be defined in an extension of the theory incorporating tensor fields of higher rank. The Standard Model contains only one-forms and zero-forms in the bosonic sector, therefore only the even part of the above graded Lie algebra — i.e. Lie[SU(2)×U(1)] — acts.

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Godfrey, Stephen. « Comment on Z′'s and the H1 and ZEUS High Q2 Anomalies ». Modern Physics Letters A 12, n^o 25 (20 août 1997) : 1859–63. http://dx.doi.org/10.1142/s0217732397001898.

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We investigate the effects of extra neutral gauge bosons on the high Q2 region of the e+p→ e+X cross-section at [Formula: see text] GeV. We found that the only models with electroweak strength coupling, typical of extended gauge theories, that give a better fit to the H1 and ZEUS high Q2 data than the standard model, are ruled out by the existing data from the Tevatron. From general scaling arguments, using the allowed contact interactions, the only allowed models with Z′'s would be those with strong couplings although even in this case the statistical evidence is not compelling.

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Nguyen, Ai Viet, et Tien Du Pham. « Non-Abelian gauge fields as components of gravity in the discretized Kaluza–Klein theory ». Modern Physics Letters A 32, n^o 18 (23 mai 2017) : 1750095. http://dx.doi.org/10.1142/s021773231750095x.

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Discretized Kaluza–Klein theory in [Formula: see text] spacetime can be constructed based on the concepts of noncommutative geometry. In this paper, we show that it is possible to incorporate the non-Abelian gauge fields in this framework. The generalized Hilbert–Einstein action is gauge invariant only in two cases. In the first case, the gauge group must be Abelian on one sheet of spacetime and non-Abelian on the other one. In the second case, the gauge group must be the same on two sheets of spacetime. Actually, the theories of electroweak and strong interactions can fit into these two cases.

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Knoepfel, Kyle J. « Standard Model Higgs boson searches at the Tevatron ». Modern Physics Letters A 29, n^o 10 (28 mars 2014) : 1430009. http://dx.doi.org/10.1142/s0217732314300092.

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We give an overview of Standard Model (SM) Higgs boson studies performed at the CDF and D∅ experiments at the Tevatron proton–antiproton collider. Combining the results of many individual analyses, most of which use the full data set available, an excess with a significance of 3.0 standard deviations with respect to the SM hypothesis is observed at a Higgs boson mass of 125 GeV /c2. At that mass, the combined best-fit cross-section is consistent with the SM prediction. Constraints are also placed on the Higgs boson couplings with fermions and electroweak vector bosons and are consistent with the SM predictions within the uncertainties.

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Devi, Kh Helensana, K. Sashikanta Singh et N. Nimai Singh. « Stability of the Next-to-Tribimaximal Mixings under Radiative Corrections with the Variation of the SUSY Breaking Scale in MSSM ». Advances in High Energy Physics 2023 (24 novembre 2023) : 1–17. http://dx.doi.org/10.1155/2023/2365316.

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We analyze the radiative stability of the next-to-tribimaximal mixings (NTBM) with the variation of the SUSY breaking scale ( m S ) in MSSM, for both normal ordering (NO) and inverted ordering (IO) at the fixed input value of the seesaw scale M R = 1 0 15 GeV and two different values of tan β . All the neutrino oscillation parameters receive varying radiative corrections irrespective of the m S values at the electroweak scale, which are all within the 3 σ range of the latest global fit data at a low value of tan β . NO is found to be more stable than IO for all four different NTBM mixing patterns.

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Stein, Nina K., et William H. Kinney. « Natural inflation after Planck 2018 ». Journal of Cosmology and Astroparticle Physics 2022, n^o 01 (1 janvier 2022) : 022. http://dx.doi.org/10.1088/1475-7516/2022/01/022.

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Abstract We calculate high-precision constraints on Natural Inflation relative to current observational constraints from Planck 2018 + BICEP/Keck(BK15) Polarization + BAO on r and n S, including post-inflationary history of the universe. We find that, for conventional post-inflationary dynamics, Natural Inflation with a cosine potential is disfavored at greater than 95% confidence out by current data. If we assume protracted reheating characterized by w̅>1/3, Natural Inflation can be brought into agreement with current observational constraints. However, bringing unmodified Natural Inflation into the 68% confidence region requires values of T re below the scale of electroweak symmetry breaking. The addition of a SHOES prior on the Hubble Constant H 0 only worsens the fit.

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Huang, Guo-Yuan, Zhi-Zhong Xing et Jing-Yu Zhu. « Spontaneous μ-τ Reflection Symmetry Breaking in Neutrino Phenomenology ». Universe 4, n^o 12 (4 décembre 2018) : 141. http://dx.doi.org/10.3390/universe4120141.

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The latest global analysis of neutrino oscillation data indicates that the normal neutrino mass ordering is favored over the inverted one at the 3 σ level. The best-fit values of the largest neutrino mixing angle θ 23 and the Dirac CP-violating phase δ are located in the higher octant and the third quadrant, respectively. We show that these experimental trends can be naturally explained by the μ - τ reflection symmetry breaking, triggered by the one-loop renormalization-group equations (RGEs) running from a superhigh energy scale down to the electroweak scale in the framework of the minimal supersymmetric standard model (MSSM). The complete parameter space is numerically explored for both the Majorana and Dirac cases, by allowing the smallest neutrino mass m 1 and the MSSM parameter tan β to vary within their reasonable ranges.

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Gonzalez-Garcia, M. C., et J. W. F. Valle. « Neutral current and LEP constraints on an extra E6 neutral gauge boson. A global fit to electroweak parameters ». Physics Letters B 259, n^o 3 (avril 1991) : 365–72. http://dx.doi.org/10.1016/0370-2693(91)90842-e.

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Novikov, V. A., L. B. Okun, A. N. Rozanov, M. I. Vysotsky et V. P. Yurov. « The values of mt and derived from the non-observation of electroweak radiative corrections at LEP : global fit ». Physics Letters B 331, n^o 3-4 (juillet 1994) : 433–40. http://dx.doi.org/10.1016/0370-2693(94)91076-6.

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Ciuchini, Marco, Enrico Franco, Satoshi Mishima, Maurizio Pierini, Laura Reina et Luca Silvestrini. « Update of the electroweak precision fit, interplay with Higgs-boson signal strengths and model-independent constraints on new physics ». Nuclear and Particle Physics Proceedings 273-275 (avril 2016) : 2219–25. http://dx.doi.org/10.1016/j.nuclphysbps.2015.09.361.

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Zhang, Ying, et Qing Wang. « Survival of new physics : Anomaly-free neutral gauge boson at the LHC ». International Journal of Modern Physics A 29, n^o 08 (24 mars 2014) : 1450046. http://dx.doi.org/10.1142/s0217751x14500468.

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An anomaly-free U(1)′ effective Lagrangian as a benchmark of new physics beyond the standard model is proposed to survey the maximal parameter space constrained by the precise electroweak measurements at the Large Electron-Positron Collider (LEP) and direct detection of the dilepton decay channel at [Formula: see text] at the Large Hadron Collider (LHC). By the global fit of the effective couplings of the Z boson to the Standard Model fermions, parameters Δ11, Δ21 and g′′Δ31 related to mixings and r related to the U(1)′ charge assignment are bounded. The allowed areas are plotted not only in the r–g′′ plane, but also in the mZ′–g′′ plane. They show that a sub-TeV Z′ is still permissible as long as the coupling g′′ is of order ~0.01. The results hint at possible new physics beyond the standard model. A prediction of the possible signal for the dilepton decay channel at [Formula: see text] at LHC is also provided.

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GURTU, A. « A CRITICAL LOOK AT PRECISION ELECTROWEAK DATA AT HIGH ENERGY—A HINT FOR PHYSICS BEYOND THE STANDARD MODEL ? » Modern Physics Letters A 09, n^o 35 (20 novembre 1994) : 3301–12. http://dx.doi.org/10.1142/s0217732394003129.

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High energy electroweak data, including the recent measurement of M top is analyzed within the basic framework of the standard model. While the experimentally measured value of [Formula: see text] implies a low value of M top , the rest of the data demands a much higher value. Estimates of M Higgs within the SM framework including and excluding this Rb measurement are given. Next this discrepancy is expressed in terms of a new parameter, [Formula: see text], the excess[Formula: see text] production compared to that expected from a SM fit. This parameter is determined to be (9.4 to 12.8) ± 5.0 MeV, implying an excess of over 10 000 [Formula: see text] events in each LEP experiment after the 1993 data is fully analyzed. The origin of these events could be non-minimal Higgs pair production which should be thoroughly searched for in the full data sample of ~2×106 events per LEP experiment. Unless this discrepancy eventually turns out to be a fluctuation one may be witnessing at LEP the advent of physics beyond the standard model.

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Panda, Dhiren, et Rukmani Mohanta. « Exploring b → cτν mediated baryonic decay modes in SMEFT framework ». EPJ Web of Conferences 312 (2024) : 04006. http://dx.doi.org/10.1051/epjconf/202431204006.

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Motivated by the interplay between the LEFT and SMEFT operators at the electroweak scale, we study the interrelation among the B decays mediated by b → cℓνℓ, b → sνℓνℓ and b → sℓℓ (ℓ = e, µ, τ) quark level transitions in the context of six-dimensional SMEFT operators such as $${Q_{\ell q}^{(3)},\,{Q_{\ell edq}},\,Q_{\ell equ}^{(1)},\,Q_{\ell equ}^{(3)},\,{\rm{and}}\,Q_{\phi q}^{(3)}} $$. We constrain the new physics parameter space through a com-ℓequ ϕq prehensive global fit incorporating the observables RD, RD∗, Pτ(D∗), FL(D∗), RΛ, B(B0 → K∗νν), B(B → K+νν), B(B → K+τ+τ−) and B(Bs → τ+τ−). We then investigate the sensitivity of new physics in the semi-leptonic decay modes of b-baryons, specifically Ξb → Ξcτ− ν¯τ. We further explore the impact of the new physics couplings on several observables such as the differential branching ratio (DBR), forward-backward asymmetry ($${A_{FB}^\tau} $$) the lepton flavor non-universality ($${R_{{\Xi _b}}} $$) for this processes.

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Bian, Ligong, Da Liu et Jing Shu. « Low scale composite Higgs model and 1.8 ∼2 TeV diboson excess ». International Journal of Modern Physics A 33, n^o 11 (20 avril 2018) : 1841007. http://dx.doi.org/10.1142/s0217751x18410075.

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We consider a simple solution to explain the recent diboson excess observed by ATLAS and CMS Collaborations in models with custodial symmetry [Formula: see text]. The [Formula: see text] triplet vector boson [Formula: see text] with mass range of [Formula: see text] TeV would be produced through the Drell–Yan process with sizable diboson decay branching to account for the excess. The other [Formula: see text] bidoublet axial vector boson [Formula: see text] would cancel all deviations of electroweak obervables induced by [Formula: see text] even if the SM fermions mix with some heavy vector-like (composite) fermions which couple to [Formula: see text] (“nonuniversally partially composite”), therefore allows arbitrary couplings between each SM fermion and [Formula: see text]. We present our model in the “General Composite Higgs” framework with [Formula: see text] breaking at scale [Formula: see text] and demand the first Weinberg sum rule and positive gauge boson form factors as the theoretical constraints. We find that our model can fit the diboson excess very well if the left-handed SM light quarks, charged leptons and tops have zero, zero/moderately small and moderate/large composite components for reasonable values of [Formula: see text] and [Formula: see text]. The correlation between tree level [Formula: see text] parameter and the [Formula: see text] suggest a large [Formula: see text] contribution to [Formula: see text] and it is indeed a [Formula: see text] effect in our parameter space which provides a strong hint for our scenario if this diboson excess is confirmed by the [Formula: see text] TeV LHC Run II.

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HAURYSH, Vadzim, et Viktor ANDREEV. « Electroweak decays of unflavored mesons in Poincaré covariant quark model ». TURKISH JOURNAL OF PHYSICS 43, n^o 2 (8 avril 2019) : 167–77. http://dx.doi.org/10.3906/fiz-1810-24.

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Balkin, Reuven, Eric Madge, Tony Menzo, Gilad Perez, Yotam Soreq et Jure Zupan. « On the implications of positive W mass shift ». Journal of High Energy Physics 2022, n^o 5 (mai 2022). http://dx.doi.org/10.1007/jhep05(2022)133.

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Abstract We investigate the phenomenological implications of the recent W mass measurement by the CDF collaboration, which exhibits tension with the standard model (SM) electroweak fit. Performing the fit to the electroweak observables within the SM effective field theory, we find that the new physics that contributes either to the determination of the electroweak vacuum expectation value, or to the oblique parameters, can improve the agreement with data. The best description is obtained from a fit where flavor universality is not required in the new physics operators, with 2 to 3 σ indications for several nonzero Wilson coefficients. We point out that top partners with order TeV masses could lead to the observed shift in the W mass.

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Bagnaschi, Emanuele, John Ellis, Maeve Madigan, Ken Mimasu, Veronica Sanz et Tevong You. « SMEFT analysis of mW ». Journal of High Energy Physics 2022, n^o 8 (31 août 2022). http://dx.doi.org/10.1007/jhep08(2022)308.

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Abstract We use the Fitmaker tool to incorporate the recent CDF measurement of mW in a global fit to electroweak, Higgs, and diboson data in the Standard Model Effective Field Theory (SMEFT) including dimension-6 operators at linear order. We find that including any one of the SMEFT operators $$ \mathcal{O} $$ O HWB, $$ \mathcal{O} $$ O HD, $$ \mathcal{O} $$ O ℓℓ or $$ {\mathcal{O}}_{H\ell}^{(3)} $$ O H ℓ 3 with a non-zero coefficient could provide a better fit than the Standard Model, with the strongest pull for $$ \mathcal{O} $$ O HD and no tension with other electroweak precision data. We then analyse which tree-level single-field extensions of the Standard Model could generate such operator coefficients with the appropriate sign, and discuss the masses and couplings of these fields that best fit the CDF measurement and other data. In particular, the global fit favours either a singlet Z′ vector boson, a scalar electroweak triplet with zero hypercharge, or a vector electroweak triplet with unit hypercharge, followed by a singlet heavy neutral lepton, all with masses in the multi-TeV range for unit coupling.

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Loizos, Bill Michael, Xuan-Gong Wang, Anthony W. Thomas, Martin White et Anthony G. Williams. « Constraints on the dark sector from electroweak precision observables ». Journal of Physics G : Nuclear and Particle Physics, 22 mai 2024. http://dx.doi.org/10.1088/1361-6471/ad4efd.

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Abstract We revisit the Standard Model fit to electroweak precision observables using the latest data and the Particle Data Group value of the mass of the W boson. This analysis is repeated for the value reported by CDF. The constraints on the parameter space for dark photons arising from these electroweak precision observables are then evaluated for both values of the W boson mass. We also extend previous work by placing the first electroweak precision observable constraints on the coupling of dark photons to the fermionic dark matter sector.

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Abt, I., A. M. Cooper-Sarkar, B. Foster, C. Gwenlan, V. Myronenko, O. Turkot et K. Wichmann. « Combined electroweak and QCD fit to HERA data ». Physical Review D 94, n^o 5 (15 septembre 2016). http://dx.doi.org/10.1103/physrevd.94.052007.

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Huang, Weicong, Jing Shu et Yue Zhang. « On the Higgs fit and electroweak phase transition ». Journal of High Energy Physics 2013, n^o 3 (mars 2013). http://dx.doi.org/10.1007/jhep03(2013)164.

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Davighi, Joe, et Joseph Tooby-Smith. « Electroweak flavour unification ». Journal of High Energy Physics 2022, n^o 9 (22 septembre 2022). http://dx.doi.org/10.1007/jhep09(2022)193.

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Abstract We propose that the electroweak and flavour quantum numbers of the Standard Model (SM) could be unified at high energies in an SU(4) × Sp(6)L× Sp(6)R anomaly-free gauge model. All the SM fermions are packaged into two fundamental fields, ΨL ∼ (4,6,1) and ΨR ∼ (4,1,6), thereby explaining the origin of three families of fermions. The SM Higgs, being electroweakly charged, necessarily becomes charged also under flavour when embedded in the UV model. It is therefore natural for its vacuum expectation value to couple only to the third family. The other components of the UV Higgs fields are presumed heavy. Extra scalars are needed to break this symmetry down to the SM, which can proceed via ‘flavour-deconstructed’ gauge groups; for instance, we propose a pattern Sp(6)L→$$ {\prod}_{i=1}^3\mathrm{SU}{(2)}_{L,i}\to \mathrm{SU}{(2)}_L $$ ∏ i = 1 3 SU 2 L , i → SU 2 L for the left-handed factor. When the heavy Higgs components are integrated out, realistic quark Yukawa couplings with in-built hierarchies are naturally generated without any further ingredients, if we assume the various symmetry breaking scalars condense at different scales. The CKM matrix that we compute is not a generic unitary matrix, but it can precisely fit the observed values.

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Banerjee, Shankha, Rick S. Gupta, Oscar Ochoa-Valeriano et Michael Spannowsky. « High energy lepton colliders as the ultimate Higgs microscopes ». Journal of High Energy Physics 2022, n^o 2 (février 2022). http://dx.doi.org/10.1007/jhep02(2022)176.

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Abstract We study standard electroweak/Higgs processes at the high-energy lepton colliders ILC and CLIC. We identify a subset of three operators in the SMEFT that give leading contributions to these processes at high energies. We then perform a ‘high-energy fit’ including these operators. Our final bounds surpass existing LEP bounds and HL-LHC projections by orders of magnitude. Furthermore, we find that these colliders can probe scales up to tens of TeV, corresponding to the highest scales explored in electroweak/Higgs physics.

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Strumia, Alessandro. « Interpreting electroweak precision data including the W-mass CDF anomaly ». Journal of High Energy Physics 2022, n^o 8 (24 août 2022). http://dx.doi.org/10.1007/jhep08(2022)248.

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Abstract We perform a global fit of electroweak data, finding that the anomaly in the W mass claimed by the CDF collaboration can be reproduced as a universal new-physics correction to the T parameter or |H†DμH|2 operator. Contributions at tree-level from multi-TeV new physics can fit the anomaly compatibly with collider bounds: we explore which scalar vacuum expectation values (such as a triplet with zero hypercharge), Z′ vectors (such as a Z′ coupled to the Higgs only), little-Higgs models or higher-dimensional geometries provide good global fits. On the other hand, new physics that contributes at loop-level must be around the weak scale to fit the anomaly. Thereby it generically conflicts with collider bounds, that can be bypassed assuming special kinematics like quasi-degenerate particles that decay into Dark Matter (such as an inert Higgs doublet or appropriate supersymmetric particles).

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Atkinson, Oliver, Matthew Black, Alexander Lenz, Aleksey Rusov et James Wynne. « Cornering the Two Higgs Doublet Model Type II ». Journal of High Energy Physics 2022, n^o 4 (avril 2022). http://dx.doi.org/10.1007/jhep04(2022)172.

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Abstract We perform a comprehensive study of the allowed parameter space of the Two Higgs Doublet Model of Type II (2HDM-II). Using the theoretical framework flavio we combine the most recent flavour, collider and electroweak precision observables with theoretical constraints to obtain bounds on the mass spectrum of the theory. In particular we find that the 2HDM-II fits the data slightly better than the Standard Model (SM) with best fit values of the heavy Higgs masses around 2 TeV and a value of tan β ≈ 4. Moreover, we conclude that the wrong-sign limit is disfavoured by Higgs signal strengths and excluded by the global fit by more than five standard deviations and potential deviations from the alignment limit can only be tiny. Finally we test the consequences of our study on electroweak baryogenesis via the program package BSMPT and we find that the allowed parameter space strongly discourages a strong first order phase transition within the 2HDM-II.

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Ellis, John, Christopher W. Murphy, Verónica Sanz et Tevong You. « Updated global SMEFT fit to Higgs, diboson and electroweak data ». Journal of High Energy Physics 2018, n^o 6 (juin 2018). http://dx.doi.org/10.1007/jhep06(2018)146.

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Allwicher, Lukas, Gino Isidori, Javier M. Lizana, Nudžeim Selimović et Ben A. Stefanek. « Third-family quark-lepton Unification and electroweak precision tests ». Journal of High Energy Physics 2023, n^o 5 (22 mai 2023). http://dx.doi.org/10.1007/jhep05(2023)179.

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Abstract We analyze the compatibility of the hypothesis of third-family quark-lepton unification at the TeV scale with electroweak precision data, lepton flavor universality tests, and high-pT constraints. We work within the framework of the UV complete flavor non-universal 4321 gauge model, which is matched at one loop to the Standard Model Effective Field Theory. For consistency, all electroweak precision observables are also computed at one loop within the effective field theory. At tree level, the most sizeable corrections are to W → τντ and Z → ντντ due to integrating out a pseudo-Dirac singlet fermion required by the model for neutrino mass generation. At loop level, the new colored states of the model generate large flavor-universal contributions to the electroweak precision observables via leading- and next-to-leading log running effects, yielding a significant improvement in the electroweak fit (including an increase in the W-boson mass). These effects cannot be decoupled if the model addresses the charged-current B-meson anomalies. Overall, we find good compatibility between the data sets, while simultaneously satisfying all low- and high-energy constraints.

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Brod, Joachim, Sandra Kvedaraitė et Zachary Polonsky. « Two-loop electroweak corrections to the Top-Quark Contribution to ϵK ». Journal of High Energy Physics 2021, n^o 12 (décembre 2021). http://dx.doi.org/10.1007/jhep12(2021)198.

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Abstract The parameter ϵK measures CP violation in the neutral kaon system. It is a sensitive probe of new physics and plays a prominent role in the global fit of the Cabibbo-Kobabyashi-Maskawa matrix. The perturbative theory uncertainty is currently dominated by the top-quark contribution. Here, we present the calculation of the full two-loop electroweak corrections to the top-quark contribution to ϵK, including the resummation of QED-QCD logarithms. We discuss different renormalization prescriptions for the electroweak input parameters. In the traditional normalization of the weak Hamiltonian with two powers of the Fermi constant GF, the top-quark contribution is shifted by −1%.

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Bernard, Véronique, Sébastien Descotes-Genon et Luiz Vale Silva. « Constraining the gauge and scalar sectors of the doublet left-right symmetric model ». Journal of High Energy Physics 2020, n^o 9 (septembre 2020). http://dx.doi.org/10.1007/jhep09(2020)088.

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Abstract We consider a left-right symmetric extension of the Standard Model where the spontaneous breakdown of the left-right symmetry is triggered by doublets. The electroweak ρ parameter is protected from large corrections in this Doublet Left-Right Model (DLRM), contrary to the triplet case. This allows in principle for more diverse patterns of symmetry breaking. We consider several constraints on the gauge and scalar sectors of DLRM: the unitarity of scattering processes involving gauge bosons with longitudinal polarisations, the radiative corrections to the muon ∆r parameter and the electroweak precision observables measured at the Z pole and at low energies. Combining these constraints within the frequentist CKMfitter approach, we see that the fit pushes the scale of left-right symmetry breaking up to a few TeV, while favouring an electroweak symmetry breaking triggered not only by the SU(2)L×SU(2)R bi-doublet, which is the case most commonly considered in the literature, but also by the SU(2)L doublet.

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Aiko, Masashi, et Motoi Endo. « Electroweak precision test of axion-like particles ». Journal of High Energy Physics 2023, n^o 5 (17 mai 2023). http://dx.doi.org/10.1007/jhep05(2023)147.

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Abstract We study the contributions of an axion-like particle to the electroweak precision observables. The particle is assumed to couple with the standard model electroweak gauge bosons. We provide the formulae of the contributions valid for any mass of the axion-like particle. It is found that the effects arise not only via the oblique S and U parameters but also via radiative corrections to the gauge couplings. Besides, the decay of Z → aγ affects the total width of the Z boson. All of those contributions are considered simultaneously in the global fit analysis of the electroweak precision observables. Also, we discuss the recent CDF result of the W-boson mass measurement. Since the model is tightly constrained by flavor and collider constraints, it is found that the discrepancy from the standard model prediction is solved only when the axion-like particle is heavier than 500 GeV and its coupling to di-photon is suppressed.

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Harigaya, Keisuke, Evan Petrosky et Aaron Pierce. « Precision electroweak tensions and a dark photon ». Journal of High Energy Physics 2024, n^o 7 (22 juillet 2024). http://dx.doi.org/10.1007/jhep07(2024)201.

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Abstract We examine how different assumptions about the hadronic vacuum polarization, the W boson mass, and the forward-backward asymmetry in b-quarks at the Z pole can impact the precision electroweak fit. We study the implications for a kinetically mixed dark photon, addressing the complementarity of precision bounds and direct searches, particularly in the case where the dark photon can decay into the dark sector, and we consider implications for future Large Hadron Collider searches. We comment on cases where the precision effects of the dark photon may not be well-described by the oblique parameters.

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Crivellin, Andreas, Fiona Kirk, Claudio Andrea Manzari et Marc Montull. « Global electroweak fit and vector-like leptons in light of the Cabibbo angle anomaly ». Journal of High Energy Physics 2020, n^o 12 (décembre 2020). http://dx.doi.org/10.1007/jhep12(2020)166.

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Abstract The “Cabibbo Angle Anomaly” (CAA) originates from the disagreement between the CKM elements Vud and Vus extracted from superallowed beta and kaon decays, respectively, once compared via CKM unitarity. It points towards new physics with a significance of up to 4 σ, depending on the theoretical input used, and can be explained through modified W couplings to leptons. In this context, vector-like leptons (VLLs) are prime candidates for a corresponding UV completion since they can affect Wℓν couplings at tree-level, such that this modification can have the dominant phenomenological impact. In order to consistently assess agreement data, a global fit is necessary which we perform for gauge-invariant dimension-6 operators and all patterns obtained for the six possible representations (under the SM gauge group) of VLLs. We find that even in the lepton flavour universal case, including the measurements of the CKM elements Vus and Vud into the electroweak fit has a relevant impact, shifting the best fit point significantly. Concerning the VLLs we discuss the bounds from charged lepton flavour violating processes and observe that a single representation cannot describe experimental data significantly better than the SM hypothesis. However, allowing for several representations of VLLs at the same time, we find that the simple scenario in which N couples to electrons via the Higgs and Σ1 couples to muons not only explains the CAA but also improves the rest of the electroweak fit in such a way that its best fit point is preferred by more than 4 σ with respect to the begin.

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Allanach, B. C., J. Eliel Camargo-Molina et Joe Davighi. « Global fits of third family hypercharge models to neutral current B-anomalies and electroweak precision observables ». European Physical Journal C 81, n^o 8 (août 2021). http://dx.doi.org/10.1140/epjc/s10052-021-09377-1.

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AbstractWhile it is known that third family hypercharge models can explain the neutral current B-anomalies, it was hitherto unclear whether the $$Z-Z^\prime $$ Z - Z ′ 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 .0007, simple versions of the models (fitting two additional parameters each) provide much improved fits. The original Third Family Hypercharge Model, for example, has a p-value of $${.065}$$ . 065 , with $$\sqrt{\Delta \chi ^2}=6.5\sigma $$ Δ χ 2 = 6.5 σ .

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Aaij, R., A. S. W. Abdelmotteleb, C. Abellan Beteta, F. Abudinén, T. Ackernley, A. A. Adefisoye, B. Adeva et al. « Measurement of the effective leptonic weak mixing angle ». Journal of High Energy Physics 2024, n^o 12 (3 décembre 2024). https://doi.org/10.1007/jhep12(2024)026.

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Abstract Using pp collision data at $$ \sqrt{s} $$ s = 13 TeV, recorded by the LHCb experiment between 2016 and 2018 and corresponding to an integrated luminosity of 5.4 fb−1, the forward-backward asymmetry in the pp → Z/γ* → μ+μ− process is measured. The measurement is carried out in ten intervals of the difference between the muon pseudorapidities, within a fiducial region covering dimuon masses between 66 and 116 GeV, muon pseudorapidities between 2.0 and 4.5 and muon transverse momenta above 20 GeV. These forward-backward asymmetries are compared with predictions, at next-to-leading order in the strong and electroweak couplings. The measured effective leptonic weak mixing angle is$$ {\sin}^2{\theta}_{\textrm{eff}}^{\ell }=0.23147\pm 0.00044\pm 0.00005\pm 0.00023, $$ sin 2 θ eff ℓ = 0.23147 ± 0.00044 ± 0.00005 ± 0.00023 , where the first uncertainty is statistical, the second arises from systematic uncertainties associated with the asymmetry measurement, and the third arises from uncertainties in the fit model used to extract $$ {\sin}^2{\theta}_{\textrm{eff}}^{\ell } $$ sin 2 θ eff ℓ from the asymmetry measurement. This result is based on an arithmetic average of results using the CT18, MSHT20, and NNPDF31 parameterisations of the proton internal structure, and is consistent with previous measurements and with predictions from the global electroweak fit.

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Bresó-Pla, Víctor, Adam Falkowski et Martín González-Alonso. « A FB in the SMEFT : precision Z physics at the LHC ». Journal of High Energy Physics 2021, n^o 8 (août 2021). http://dx.doi.org/10.1007/jhep08(2021)021.

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Abstract We study the forward-backward asymmetry AFB in pp → ℓ+ℓ− at the Z peak within the Standard Model Effective Field Theory (SMEFT). We find that this observable provides per mille level constraints on the vertex corrections of the Z boson to quarks, which close a flat direction in the electroweak precision SMEFT fit. Moreover, we show that current AFB data is precise enough so that its inclusion in the fit improves significantly LEP bounds even in simple New Physics setups. This demonstrates that the LHC can compete with and complement LEP when it comes to precision measurements of the Z boson properties.

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Baak, M., M. Goebel, J. Haller, A. Hoecker, D. Kennedy, K. Mönig, M. Schott et J. Stelzer. « Updated status of the global electroweak fit and constraints on new physics ». European Physical Journal C 72, n^o 5 (mai 2012). http://dx.doi.org/10.1140/epjc/s10052-012-2003-4.

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Ellis, John, Maeve Madigan, Ken Mimasu, Veronica Sanz et Tevong You. « Top, Higgs, diboson and electroweak fit to the Standard Model effective field theory ». Journal of High Energy Physics 2021, n^o 4 (avril 2021). http://dx.doi.org/10.1007/jhep04(2021)279.

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Abstract The search for effective field theory deformations of the Standard Model (SM) is a major goal of particle physics that can benefit from a global approach in the framework of the Standard Model Effective Field Theory (SMEFT). For the first time, we include LHC data on top production and differential distributions together with Higgs production and decay rates and Simplified Template Cross-Section (STXS) measurements in a global fit, as well as precision electroweak and diboson measurements from LEP and the LHC, in a global analysis with SMEFT operators of dimension 6 included linearly. We present the constraints on the coefficients of these operators, both individually and when marginalised, in flavour-universal and top-specific scenarios, studying the interplay of these datasets and the correlations they induce in the SMEFT. We then explore the constraints that our linear SMEFT analysis imposes on specific ultra-violet completions of the Standard Model, including those with single additional fields and low-mass stop squarks. We also present a model-independent search for deformations of the SM that contribute to between two and five SMEFT operator coefficients. In no case do we find any significant evidence for physics beyond the SM. Our underlying Fitmaker public code provides a framework for future generalisations of our analysis, including a quadratic treatment of dimension-6 operators.

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Lu, Chih-Ting, Lei Wu, Yongcheng Wu et Bin Zhu. « Electroweak precision fit and new physics in light of the W boson mass ». Physical Review D 106, n^o 3 (29 août 2022). http://dx.doi.org/10.1103/physrevd.106.035034.

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