Articles de revues : « EW Bosons »

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KIM, JIHN E., HANS PETER NILLES et MIN-SEOK SEO. « SINGLET SUPERFIELD EXTENSION OF THE MINIMAL SUPERSYMMETRIC STANDARD MODEL WITH PECCEI–QUINN SYMMETRY AND A LIGHT PSEUDOSCALAR HIGGS BOSON AT THE LHC ». Modern Physics Letters A 27, n^o 29 (17 septembre 2012) : 1250166. http://dx.doi.org/10.1142/s0217732312501660.

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Motivated by the μ-problem and the axion solution to the strong CP-problem, we extend the MSSM with one more chiral singlet field X ew . The underlying PQ-symmetry allows only one more renormalizable term X ew Hu Hd in the superpotential. The spectrum of the Higgs system includes a light pseudoscalar aX (in addition to the standard CP-even Higgs boson), predominantly decaying to two photons: aX →γγ. Both Higgs bosons might be in the range accessible to current LHC experiments.

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Accomando, Elena. « Bounds on Kaluza–Klein states from EWPT and direct searches at the LHC ». Modern Physics Letters A 30, n^o 15 (7 mai 2015) : 1540010. http://dx.doi.org/10.1142/s0217732315400106.

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We review the present bounds on Kaluza–Klein (KK)-excitations of Standard Model gauge bosons, predicted by TeV size extra dimensions, which have been set by the ElectroWeak Precision Test (EWPT) and recently by the direct searches performed at the CERN Large Hadron Collider (LHC). Concerning the theoretical framework we present results for the Non-Universal Extra Dimension (NUED) model with matter localized at the boundaries and all gauge bosons propagating into the bulk and acquiring KK-excitations. We also discuss its simplified version, NUED(EW), where only the ElectroWeak SM gauge bosons are allowed to propagate in the extra dimension, and its next-to-minimal version ElectroWeak Universal Extra Dimension (UED)(EW) where SU(3) is localized on the brane while the SU(2)×U(1) particle content fully propagates into the bulk.

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PANTELIDES, SOKRATES T. « A NEW THEORY OF ELECTROMAGNETIC, WEAK AND STRONG INTERACTIONS ». International Journal of Modern Physics E 11, n^o 03 (juin 2002) : 177–210. http://dx.doi.org/10.1142/s0218301302000806.

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The Higgs mechanism for imparting masses to gauge bosons and matter particles is obviated by showing that Yang–Mills gauge bosons have intrinsic nonzero masses (rest-frame energies) from self-interactions. Electroweak (EW) mixing is ruled out because it produces a photon field that is massive, carries EW charge, and does not satisfy Maxwell's equations. Other fundamental difficulties of the Standard Model are identified. A new gauge theory of electromagnetic, weak and strong interactions is derived from the Dirac equation with no other postulates and no free parameters. The three forces are intrinsically unified, the photon field is Maxwellian, weak interactions derive from spin (not isospin), and the weak and strong bosons are naturally massive and chiral. Charge is naturally quantized to integral values. Three generations of lepton pairs and elementary-hadron pairs, all with integral charges, are predicted, contradicting the phenomenology of fractional quark charges, but in full accord with experimental data on weak and strong processes and composite hadrons. Neutrinos are massive. The Dirac masses, the fine structure constant, neutrino oscillations and Cabibbo mixing are shown to have a common origin in the gravitational field. The new theory leads to a new interpretation of "negative energies" with cosmological implications. Finally, it is shown that key expressions of the EW formalism agree with those of the new theory and with experiments only if the mixing angle θ is given by sin 2 θ = 0.25, which accounts for the EW model's successes.

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Hosotani, Yutaka. « Gauge-Higgs EW and grand unification ». International Journal of Modern Physics A 31, n^o 20n21 (27 juillet 2016) : 1630031. http://dx.doi.org/10.1142/s0217751x16300313.

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Four-dimensional Higgs field is identified with the extra-dimensional component of gauge potentials in the gauge-Higgs unification scenario. [Formula: see text] gauge-Higgs EW unification in the Randall–Sundrum warped space is successful at low energies. The Higgs field appears as an Aharonov–Bohm phase [Formula: see text] in the fifth dimension. Its mass is generated at the quantum level and is finite. The model yields almost the same phenomenology as the standard model for [Formula: see text], and predicts [Formula: see text] bosons around 6–10 TeV with very broad widths. The scenario is generalized to [Formula: see text] gauge-Higgs grand unification. Fermions are introduced in the spinor and vector representations of [Formula: see text]. Proton decay is naturally forbidden.

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Rossi, Giancarlo. « A road towards a beyond the Standard Model model ». EPJ Web of Conferences 258 (2022) : 06003. http://dx.doi.org/10.1051/epjconf/202225806003.

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In this talk we describe examples of renormalizable strongly interacting field theories where chiral symmetry, broken at the UV cutoff by the presence of some irrelevant d > 4 operators in the fundamental Lagrangian, is recovered at low energy owing to the tuning of certain Lagrangian parameters. The interference of UV effects with IR features coming from the spontaneous breaking of the recovered chiral symmetry yields non perturbatively generated elementary fermion masses parametrically expressed by formulae of the kind mq ~ Cq(α)ΛRGI with α the gauge coupling constant and ΛRGI the RGI scale of the theory. Upon introducing EW interactions, this mechanism can be extended to give mass to EW bosons and leptons and can thus be used as an alternative to the Higgs scenario. In order to give the top quark and the weak gauge bosons a mass of the phenomenologically correct order of magnitude, the model must necessarily include (yet unobserved) super-strongly interacting massive fermions endowed, besides ordinary Standard Model interactions, with super-strong interactions with a RGI scale, ΛT ΛQCD in the few TeV range. Though limited in its scope (here we ignore hypercharge and leptons and discuss only the case of one family neglecting weak isospin splitting), the model opens the way to a solution of the naturalness problem and an understanding of the fermion mass hierarchy.

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PARK, GYE T., et T. K. KUO. « INCLUSION OF $Z \to b\bar{b}$ VERTEX CORRECTIONS IN PRECISION ELECTROWEAK TESTS ON THE Sp(6)L× U(1)Y MODEL ». International Journal of Modern Physics A 10, n^o 30 (10 décembre 1995) : 4387–97. http://dx.doi.org/10.1142/s0217751x95002035.

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We extend our previous work on the precision electroweak tests in the Sp (6)L× U (1)Y family model to include for the first time the important [Formula: see text] vertex corrections encoded in a new variable ∊b, utilizing all the latest LEP data. We include in our analysis the one-loop EW radiative corrections due to the new bosons in terms of ∊1,b and ΔΓZ. We find that the correlation between ∊1 and ∊b makes the combined constraint much stronger than the individual ones. The model is consistent with the recent CDF result of [Formula: see text] but it; cannot accommodate mt≳195 GeV .

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Das, C., L. Laperashvili, H. Nielsen et B. Sidharth. « Explaining Defects of the Universal Vacua with Black Holes-Hedgehogs and Strings ». Universe 5, n^o 3 (12 mars 2019) : 78. http://dx.doi.org/10.3390/universe5030078.

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Assuming the Multiple Point Principle (MPP) as a new law of Nature, we considered the existence of the two degenerate vacua of the Universe: (a) the first Electroweak (EW) vacuum at v 1 ≈ 246 GeV—“true vacuum”, and (b) the second Planck scale “false vacuum” at v 2 ∼ 10 18 GeV. In these vacua, we investigated different topological defects. The main aim of the paper is an investigation of the black-hole-hedgehogs configurations as defects of the false vacuum. In the framework of the f ( R ) gravity, described by the Gravi-Weak unification model, we considered a black-hole solution, which corresponds to a “hedgehog”—global monopole, that has been “swallowed” by the black-hole with mass core M B H ∼ 10 18 GeV and radius δ ∼ 10 − 21 GeV − 1 . Considering the results of the hedgehog lattice theory in the framework of the S U ( 2 ) Yang-Mills gauge-invariant theory with hedgehogs in the Wilson loops, we have used the critical value of temperature for the hedgehogs’ confinement phase ( T c ∼ 10 18 GeV). This result gave us the possibility to conclude that the SM shows a new physics (with contributions of the S U ( 2 ) -triplet Higgs bosons) at the scale ∼10 TeV. This theory predicts the stability of the EW-vacuum and the accuracy of the MPP.

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Sidharth, B. G., C. R. Das, L. V. Laperashvili et H. B. Nielsen. « Gravitational black-holes-hedgehogs and two degenerate vacua of the Universe ». International Journal of Modern Physics D 27, n^o 03 (février 2018) : 1850022. http://dx.doi.org/10.1142/s0218271818500220.

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In the present paper, assuming the Multiple Point Principle (MPP) as a new law of Nature, we considered the existence of the two degenerate vacua of the Universe: the first Electroweak (EW) vacuum at [Formula: see text][Formula: see text]GeV — “true vacuum”, and the second Planck scale “false vacuum” at [Formula: see text] GeV. In these vacua, we investigated different topological defects. The main aim of this paper is an investigation of the black-hole-hedgehogs configurations as defects of the false vacuum. In the framework of the [Formula: see text] gravity, described by the Gravi-Weak unification model, we considered a black-hole solution, which corresponds to a “hedgehog” — global monopole, that has been “swallowed” by the black-hole with mass core [Formula: see text][Formula: see text]GeV and radius [Formula: see text][Formula: see text]GeV[Formula: see text]. Considering the results of the hedgehog lattice theory in the framework of the [Formula: see text] Yang–Mills gauge-invariant theory with hedgehogs in the Wilson loops, we have used the critical value of temperature for the hedgehogs confinement phase ([Formula: see text][Formula: see text]GeV). This result gave us the possibility to conclude that the SM shows a new physics with contributions of the [Formula: see text]-triplet Higgs bosons at the scale [Formula: see text][Formula: see text]TeV. Theory predicts the stability of the EW-vacuum and the accuracy of the MPP.

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Tawfik, Abdel Nasser, et Carsten Greiner. « Early Universe Thermodynamics and Evolution in Nonviscous and Viscous Strong and Electroweak Epochs : Possible Analytical Solutions ». Entropy 23, n^o 3 (28 février 2021) : 295. http://dx.doi.org/10.3390/e23030295.

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Based on recent perturbative and non-perturbative lattice calculations with almost quark flavors and the thermal contributions from photons, neutrinos, leptons, electroweak particles, and scalar Higgs bosons, various thermodynamic quantities, at vanishing net-baryon densities, such as pressure, energy density, bulk viscosity, relaxation time, and temperature have been calculated up to the TeV-scale, i.e., covering hadron, QGP, and electroweak (EW) phases in the early Universe. This remarkable progress motivated the present study to determine the possible influence of the bulk viscosity in the early Universe and to understand how this would vary from epoch to epoch. We have taken into consideration first- (Eckart) and second-order (Israel–Stewart) theories for the relativistic cosmic fluid and integrated viscous equations of state in Friedmann equations. Nonlinear nonhomogeneous differential equations are obtained as analytical solutions. For Israel–Stewart, the differential equations are very sophisticated to be solved. They are outlined here as road-maps for future studies. For Eckart theory, the only possible solution is the functionality, H(a(t)), where H(t) is the Hubble parameter and a(t) is the scale factor, but none of them so far could to be directly expressed in terms of either proper or cosmic time t. For Eckart-type viscous background, especially at finite cosmological constant, non-singular H(t) and a(t) are obtained, where H(t) diverges for QCD/EW and asymptotic EoS. For non-viscous background, the dependence of H(a(t)) is monotonic. The same conclusion can be drawn for an ideal EoS. We also conclude that the rate of decreasing H(a(t)) with increasing a(t) varies from epoch to epoch, at vanishing and finite cosmological constant. These results obviously help in improving our understanding of the nucleosynthesis and the cosmological large-scale structure.

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ARBUZOV, BORIS A., et IVAN V. ZAITSEV. « CDF Wjj ANOMALY AS A NONPERTURBATIVE EFFECT OF THE ELECTROWEAK INTERACTION ». International Journal of Modern Physics A 27, n^o 03n04 (10 février 2012) : 1250012. http://dx.doi.org/10.1142/s0217751x12500121.

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The recently reported CDF excess at 120–160 GeV in invariant mass distribution of jet pairs accompanying W-boson1 is tentatively interpreted as a bound state of two W decaying to quark–antiquark pair. Nonperturbative effects of EW interaction obtained by application of Bogoliubov compensation approach lead to such bound state due to existence of anomalous three-boson gauge-invariant effective interaction. The application of this scheme gives satisfactory agreement with existing data without any adjusting parameter but the bound state mass 145 GeV.

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Ocalan, Kadir. « EW radiative corrections to theory predictions of charge asymmetry for W-boson hadroproduction ». Physica Scripta 97, n^o 7 (23 juin 2022) : 075305. http://dx.doi.org/10.1088/1402-4896/ac789a.

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Abstract The higher-order predictions of the lepton charge asymmetry A η l (the W-boson charge asymmetry A y W ) 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 A η l 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 A η l ( A y W ) 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 A η l 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 A η l ( A y W ) 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 A η l ( A y W ) 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 A η l contrary to the central η l region, and is sizable in some of the y W ranges of the A y W . The paper suggests inclusion of the presented EW corrections at NLO to have explicit accounting for the EW effects for the A η l ( A y W ) in phenomenological studies.

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Kamenik, Jernej F. « Flavor constraints on new physics ». Modern Physics Letters A 29, n^o 22 (16 juillet 2014) : 1430021. http://dx.doi.org/10.1142/s0217732314300213.

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We review the recent progress in our theoretical understanding of flavor-changing processes. The overall excellent agreement with the corresponding measurements allows to derive severe constraints on possible extensions of the Standard Model (SM). The important interplay between flavor, electroweak (EW) and Higgs boson probes of new phenomena is emphasized. Once the EW hierarchy problem is confronted with null results from searches for direct production of new particles at the LHC, a case can be made against purely flavor trivial new physics (NP) at the TeV scale. Theory implications of the few open experimental flavor puzzles are also briefly discussed.

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POMAROL, ALEX. « STRONGLY INTERACTING ELECTROWEAK THEORIES AND THEIR FIVE-DIMENSIONAL ANALOGS AT THE LHC ». International Journal of Modern Physics A 24, n^o 01 (10 janvier 2009) : 61–80. http://dx.doi.org/10.1142/s0217751x09042785.

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Strongly interacting theories of electroweak (EW) symmetry breaking provide an elegant solution to the hierarchy problem. In these models the EW symmetry can either be broken without a Higgs or by means of a composite Higgs boson. These scenarios have been recently investigated in the framework of five-dimensional warped models that, according to the AdS/CFT correspondence, have a four-dimensional holographic interpretation in terms of strongly coupled field theories. We describe the minimal Higgsless and composite Higgs model and show how they can successfully pass all the electroweak precision tests and solve the flavor problems. We explore the implications of these models at the LHC (Large Hadron Collider).

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Li, Bing An. « CURRENT ALGEBRA BASED EFFECTIVE CHIRAL THEORY OF MESONS AND A NEW EW THEORY ». International Journal of Modern Physics A 21, n^o 04 (10 février 2006) : 950–53. http://dx.doi.org/10.1142/s0217751x06032393.

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A current algebra based effective chiral theory of pseudoscalar, vector, axial-vector mesons is reviewed. A new mechanism generating the masses and guage fixing terms of gauge boson is revealed from this effective theory. A EW theory without Higgs is proposed. The masses and gauge fixing terms of W and Z are dynamically generated. Three heavy scalar fields are dynamically generated too. They are ghosts.

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Li, Tianjun, Wenyu Wang, Xiao-Chuan Wang et Zhao-Hua Xiong. « The analytical one-loop contributions to Higgs boson mass in the Supersymmetric Standard Model with vector-like particles ». International Journal of Modern Physics A 32, n^o 33 (30 novembre 2017) : 1745002. http://dx.doi.org/10.1142/s0217751x17450026.

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In this paper, we extend the Minimal Supersymmetric Standard Model (MSSM) with additional vector-like particles (VLPs) and compared the differences of mass spectrum and Feynman rules between the MSSM and MSSMV. We analytically calculate the one loop contributions to the Higgs boson mass from the fermions and sfermions in the on shell renormalization scheme. After discussing and numerically analyzing cases without bilinear terms and a case with a (partial) decoupling limit, we find: (i) the corrections depend on the mass splittings between quarks and squarks and between vector-like fermions and their sfermions; (ii) there exists the (partial) decoupling limit, where the VLPs decouple from the electroweak (EW) energy scale, even when one of the VLPs is light around the EW scale. The reason is that the contributions to Higgs mass can be suppressed by the (or partial) decoupling effects, which can make the EW phenomenology different from the MSSM. Moreover, we present some numerical analysis to understand these unique features.

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Ogul, Hasan, et Kamuran Dilsiz. « Cross Section Prediction for Inclusive Production of Z Boson in pp Collisions at s=14 TeV : A Study of Systematic Uncertainty due to Scale Dependence ». Advances in High Energy Physics 2017 (2017) : 1–8. http://dx.doi.org/10.1155/2017/8262018.

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Prediction of Z→l+l- production cross section (where l±=e±,μ±) in proton-proton collisions at s=14 TeV is estimated up to next-to-next-to-leading order (NNLO) in perturbative QCD including next-to-leading order (NLO) electroweak (EW) corrections. The total inclusive Z boson production cross section times leptonic branching ratio, within the invariant mass window 66<mll<116 GeV, is predicted using NNLO HERAPDF2.0 at NNLO QCD and NLO EW as σZTot=2111.69-26.92+26.31 (PDF) ±11 (αs) ±17 (scale) -30.98+57.41 (parameterization and model). Theoretical prediction of the fiducial cross section is further computed with the latest modern PDF models (CT14, MMHT2014, NNPDF3.0, HERAPDF2.0, and ABM12) at NNLO for QCD and NLO for EW. The central values of the predictions are based on DYNNLO 1.5 program and the uncertainties are extracted using FEWZ 3.1 program. In addition, the cross section is also calculated as functions of μR and μF scales. The choice of μR and μF for scale variation uncertainty is further discussed in detail.

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Kallweit, S., J. M. Lindert, P. Maierhöfer, S. Pozzorini et M. Schönherr. « NLO QCD+EW predictions for V + jets including off-shell vector-boson decays and multijet merging ». Journal of High Energy Physics 2016, n^o 4 (avril 2016) : 1–51. http://dx.doi.org/10.1007/jhep04(2016)021.

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Maznas, Ioannis. « Observation of ZZ production via Vector Boson Scattering in ATLAS ». Journal of Physics : Conference Series 2105, n^o 1 (1 novembre 2021) : 012013. http://dx.doi.org/10.1088/1742-6596/2105/1/012013.

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Abstract This document presents measurement results of the ZZ production via Vector Boson Scattering interactions in 139fb −1 of data recorded by the ATLAS detector from pp collisions at s = 13 TeV during LHC Run-II (2015-2018). In this study, 127 candidate events with a fully leptonic final state (ℓℓℓℓjj) have been observed and another 82 events for ℓℓvvjj final state, with a contribution of the purely electroweak ZZjj process estimated to be 20.6 ± 2.5 and 12.3 ± 0.7 events respectively. The measured cross sections were found to be 1.27 ± 0.14fb (1.22 ± 0.35fb) for ℓℓℓℓjj (ℓℓvvjj) in their respective fiducial regions. Using multivariant methods, the EW production of ZZjj events (combining the ℓℓℓℓjj and ℓℓvvjj channels) was measured to have a signal strength of 1.35± 0.34, which leads to a rejection of the no-electroweak hypothesis with a statistical significance of 5.5σ.

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Covarelli, Roberto, Mathieu Pellen et Marco Zaro. « Vector-Boson scattering at the LHC : Unraveling the electroweak sector ». International Journal of Modern Physics A 36, n^o 16 (31 mai 2021) : 2130009. http://dx.doi.org/10.1142/s0217751x2130009x.

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Vector-boson scattering (VBS) processes probe the innermost structure of electroweak (EW) interactions in the Standard Model (SM), and provide a unique sensitivity for new physics phenomena affecting the gauge sector. In this review, we report on the salient aspects of this class of processes, both from the theory and experimental point of view. We start by discussing recent achievements relevant for their theoretical description, some of which have set important milestones in improving the precision and accuracy of the corresponding simulations. We continue by covering the development of experimental techniques aimed at detecting these rare processes and improving the signal sensitivity over large backgrounds. We then summarize the details of the most relevant VBS signatures and review the related measurements available to date, along with their comparison with SM predictions. We conclude by discussing the perspective at the upcoming Large Hadron Collider runs and at future hadron facilities.

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Pasechnik, Roman, Vitaly Beylin, Vladimir Kuksa et Grigory Vereshkov. « Composite scalar dark matter from vector-like SU(2) confinement ». International Journal of Modern Physics A 31, n^o 08 (14 mars 2016) : 1650036. http://dx.doi.org/10.1142/s0217751x16500366.

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A toy-model with [Formula: see text] dynamics confined at high scales [Formula: see text] enables to construct Dirac UV completion from the original chiral multiplets predicting a vector-like nature of their weak interactions consistent with electroweak precision tests. In this work, we investigate a potential of the lightest scalar baryon-like (T-baryon) state [Formula: see text] with mass [Formula: see text] predicted by the simplest two-flavor vector-like confinement model as a dark matter (DM) candidate. We show that two different scenarios with the T-baryon relic abundance formation before and after the electroweak (EW) phase transition epoch lead to symmetric (or mixed) and asymmetric DM, respectively. Such a DM candidate evades existing direct DM detection constraints since its vector coupling to [Formula: see text] boson absents at tree level, while one-loop gauge boson mediated contribution is shown to be vanishingly small close to the threshold. The dominating spin-independent (SI) T-baryon–nucleon scattering goes via tree-level Higgs boson exchange in the [Formula: see text]-channel. The corresponding bound on the effective T-baryon–Higgs coupling has been extracted from the recent LUX data and turns out to be consistent with naive expectations from the light technipion case [Formula: see text]. The latter provides the most stringent phenomenological constraint on strongly-coupled [Formula: see text] dynamics so far. Future prospects for direct and indirect scalar T-baryon DM searches in astrophysics as well as in collider measurements have been discussed.

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Ocalan, Kadir. « Accurate prediction of the Drell-Yan ϕη* distribution in wide dilepton mass and rapidity ranges in pp collisions through NNLO+N³LL ». Physica Scripta 96, n^o 12 (1 décembre 2021) : 125323. http://dx.doi.org/10.1088/1402-4896/ac3e19.

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Abstract This paper presents high-accuracy predictions for the differential cross ss as a function of the key observable ϕ η * of the neutral-current Drell-Yan (DY) dilepton production in proton-proton (pp) collisions. The differential distributions for the ϕ η * are presented by using the state-of-the-art predictions from the combined calculations of fixed-order perturbative quantum chromodynamics (QCD) corrections at next-to-next-to-leading order (NNLO) accuracy and resummation of large logarithmic terms at next-to-next-to-leading logarithmic (NNLL) and next-to-NNLL (N3LL) accuracies, i.e., NNLO+NNLL and NNLO+N3LL, respectively. The predicted distributions are reported for a thorough set of the DY dilepton invariant mass m ll ranges, spanning a wide kinematic region of 50 < m ll < 1000 GeV both near and away from the Z-boson mass peak, and rapidity y ll ranges in the central detector acceptance region of ∣y ll ∣ < 2.4. The differential ϕ η * distributions in the wide m ll and y ll ranges offer stringent tests to assess the reliability of the predictions, where the m ll and y ll are closely correlated with the parton distribution functions (PDFs) of the incoming partons. The matched predictions through NNLO+N3LL are observed to provide good description of the 13 TeV pp collision data for the ϕ η * (including the dilepton transverse momentum p T ll as well) distributions in almost the entire m ll and y ll ranges, apart from the intermediate- to high- ϕ η * region in the lowest mass range 50–76 GeV which is assessed to constitute a challenge for the presented predictions. The predictions at NNLO+N3LL are also reported at 14 TeV for the upcoming high-luminosity running era of the Large Hadron Collider (LHC), in which increasing amount of data is expected to require more accurate and precise theoretical description. The most recent PDF models MSHT20 and CT18, in addition to the NNPDF3.1, are tested for the first time for the matched predictions of the ϕ η * distribution. The differential distributions by the combined predictions through NNLO QCD+NLO EW are finally provided to enable assessment of the impact of the EW corrections for the ϕ η * .

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Bao, Yunjia, JiJi Fan et Lingfeng Li. « Electroweak ALP searches at a muon collider ». Journal of High Energy Physics 2022, n^o 8 (26 août 2022). http://dx.doi.org/10.1007/jhep08(2022)276.

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Abstract A high-energy muon collider with center-of-mass energy around and above 10 TeV is also a vector boson fusion (VBF) machine, due to the significant virtual electroweak (EW) gauge boson content of high-energy muon beams. This feature, together with the clean environment, makes it an ideal collider to search for TeV-scale axion-like particles (ALP) coupling to Standard Model EW gauge bosons, which current and other future colliders have limited sensitivities to. We present detailed analyses of heavy ALP searches in both the VBF and associated production channels at a muon collider with different running benchmarks. We also show projected constraints on the ALP couplings in the effective field theory, including an operator with its coefficient not determined by the mixed Peccei-Quinn anomaly. We demonstrate that a muon collider could probe new ALP parameter space and push the sensitivities of the couplings between the ALP and EW gauge bosons by one order of magnitude compared to HL-LHC. The projected limits and search strategies for ALPs could also be applied to other types of resonances coupling to EW gauge bosons.

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Bredt, Pia M., Wolfgang Kilian, Jürgen Reuter et Pascal Stienemeier. « NLO electroweak corrections to multi-boson processes at a muon collider ». Journal of High Energy Physics 2022, n^o 12 (27 décembre 2022). http://dx.doi.org/10.1007/jhep12(2022)138.

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Abstract We present results on NLO electroweak (EW) corrections to multiple massive boson production processes at a future muon collider. Inclusive cross sections with $$ \mathcal{O} $$ O (α) corrections for processes for up to four bosons in the final state as well as differential distributions for HZ production are computed for $$ \sqrt{s} $$ s = 3, 10 and 14 TeV by using FKS subtraction in the NLO EW automated Monte-Carlo framework WHIZARD+RECOLA. Large logarithmic effects due to collinear ISR and EW virtual correction factors as well as the impacts of an energy cut on hard photons are discussed with an emphasis on the properties of Higgsstrahlung. The potential of a proposed muon collider for studying physics of the EW sector is underlined by the EW corrections significantly affecting observables for processes at high energies and boson multiplicities.

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Ruiz, Richard, Antonio Costantini, Fabio Maltoni et Olivier Mattelaer. « The Effective Vector Boson Approximation in high-energy muon collisions ». Journal of High Energy Physics 2022, n^o 6 (juin 2022). http://dx.doi.org/10.1007/jhep06(2022)114.

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Abstract Due to the inclination for forward gauge radiation, lepton colliders beyond a few TeV are effectively electroweak (EW) boson colliders, suggesting the treatment of EW bosons as constituents of high-energy leptons. In the context of a muon collider, we revisit the validity of W and Z parton distribution functions (PDFs) at leading order in 2 → n process. We systematically investigate universal and quasi-universal power-law and logarithmic corrections that arise when deriving (polarized) weak boson PDFs in the collinear limit. We go on to survey a multitude of 2 → n processes at $$ \sqrt{s} $$ s = 2–30 TeV via polarized and unpolarized EW boson fusion/scattering. To conduct this study, we report a public implementation of the Effective W/Z and Weizsäcker-Williams Approximations, which we collectively call the Effective Vector Boson Approximation, into the Monte Carlo event generator MadGraph5_aMC@NLO. This implementation lays the groundwork for developing matrix-element matching prescriptions involving EW parton showers and renormalized EW PDFs. To further with this agenda, we give recommendations on using W/Z PDFs.

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Masouminia, M. R., et P. Richardson. « Implementation of angularly ordered electroweak parton shower in Herwig 7 ». Journal of High Energy Physics 2022, n^o 4 (avril 2022). http://dx.doi.org/10.1007/jhep04(2022)112.

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Abstract We discuss the necessary steps for implementing an angularly ordered (AO) electroweak (EW) parton shower in Herwig 7 multi-purpose event generator. This includes calculating the helicity-dependent quasi-collinear EW branching functions that correspond to the full range of final-state EW parton shower, in addition to the initial-state EW gauge vector boson radiations. The results are successfully embedded in the AO Herwig 7 shower algorithm and have undergone a set of comprehensive and conclusive performance tests. Furthermore, we have used this EW parton shower algorithm, alongside the existing QCD + QED AO shower, to predict the angular distributions of W± bosons in LHC events with high transverse momentum jets. These results are compared against the explicitly generated underlying events as well as the existing ATLAS data to show the effectiveness of the newly implemented QCD + QED + EW AO parton shower scheme.

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26

Bothmann, Enrico, Davide Napoletano, Marek Schönherr, Steffen Schumann et Simon Luca Villani. « Higher-order EW corrections in ZZ and ZZj production at the LHC ». Journal of High Energy Physics 2022, n^o 6 (juin 2022). http://dx.doi.org/10.1007/jhep06(2022)064.

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Abstract We consider the production of a pair of Z bosons at the LHC and study the inclusion of EW corrections in theoretical predictions at fixed order and based on multijet-merged parton-shower simulations. To this end we present exact NLO EW results for pp → e+e−μ+μ−, and, for the first time, for pp → e+e−μ+μ−j, and compare them to the EW virtual and NLL Sudakov approximation. We then match the exact NLO EW result to the resummed Sudakov logarithms to achieve an improved $$ \mathrm{NLO}\ \mathrm{EW}+\mathrm{NLL}\ {\mathrm{EW}}_{\mathrm{sud}}^{\mathrm{exp}} $$ NLO EW + NLL EW sud exp result.Further, we discuss the inclusion of the above EW corrections in MePs@Nlo event simulations in the framework of the Sherpa event generator. We present detailed phenomenological predictions for inclusive ZZ and ZZj production taking into account the dominant EW corrections through the EW virtual approximation, as well as through (exponentiated) EW Sudakov logarithms.

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27

Han, Tao, Yang Ma et Keping Xie. « Quark and gluon contents of a lepton at high energies ». Journal of High Energy Physics 2022, n^o 2 (février 2022). http://dx.doi.org/10.1007/jhep02(2022)154.

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Abstract In high-energy leptonic collisions, such as at a multi-TeV muon collider, the collinear splittings of the electroweak (EW) gauge bosons and leptons are the dominant phenomena, and the scattering processes should thus be formulated in terms of the EW parton distribution functions (EW PDFs). We complete this formalism in the Standard Model to include the QCD sector and evaluate the quark and gluon PDFs inside a lepton at the double-log accuracy. The splittings of the photon and subsequently the quarks and gluons control the quark/gluon PDFs below the EW scale. The massive gauge bosons lead to substantial contributions at high scales. The jet production cross section can reach the order of a few nb (50 pb) in e+e−(μ+μ−) collisions, at the TeV c.m. energies with a moderate acceptance cut, that governs the overall event shape up to about $$ {p}_T^j $$ p T j ∼ 60 GeV. To complete the picture, we also provide an estimation of the total cross section for the photon-induced hadronic production at low partonic energies, which can reach the level of one hundred or a few tens of nb in high-energy electron or muon collisions.

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Denner, Ansgar, Robert Franken, Mathieu Pellen et Timo Schmidt. « NLO QCD and EW corrections to vector-boson scattering into ZZ at the LHC ». Journal of High Energy Physics 2020, n^o 11 (novembre 2020). http://dx.doi.org/10.1007/jhep11(2020)110.

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Abstract We present the first calculation of the full next-to-leading-order electroweak and QCD corrections for vector-boson scattering (VBS) into a pair of Z bosons at the LHC. We consider specifically the process pp → e+e−μ+μ−jj + X at orders $$ \mathcal{O} $$ O (α7) and $$ \mathcal{O} $$ O (αsα6) and take all off-shell and interference contributions into account. Owing to the presence of enhanced Sudakov logarithms, the electroweak corrections amount to −16% of the leading-order electroweak fiducial cross section and induce significant shape distortions of differential distributions. The QCD corrections on the other hand are larger (+24%) than typical QCD corrections in VBS. This originates from considering the full computation including tri-boson contributions in a rather inclusive phase space. We also provide a leading-order analysis of all contributions to the cross section for pp → e+e−μ+μ−jj + X in a realistic setup.

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Denner, Ansgar, et Giovanni Pelliccioli. « NLO EW and QCD corrections to polarized ZZ production in the four-charged-lepton channel at the LHC ». Journal of High Energy Physics 2021, n^o 10 (octobre 2021). http://dx.doi.org/10.1007/jhep10(2021)097.

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Abstract Measuring the polarization of electroweak bosons at the LHC allows for important tests of the electroweak-symmetry-breaking mechanism that is realized in nature. Therefore, precise Standard Model predictions are needed for the production of polarized bosons in the presence of realistic kinematic selections. We formulate a method for the calculation of polarized cross-sections at NLO that relies on the pole approximation and the separation of polarized matrix elements at the amplitude level. In this framework, we compute NLO-accurate cross-sections for the production of two polarized Z bosons at the LHC, including for the first time NLO EW corrections and combining them with NLO QCD corrections and contributions from the gluon-induced process.

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30

Denner, Ansgar, et Giovanni Pelliccioli. « NLO EW and QCD corrections to polarized ZZ production in the four-charged-lepton channel at the LHC ». Journal of High Energy Physics 2021, n^o 10 (octobre 2021). http://dx.doi.org/10.1007/jhep10(2021)097.

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Abstract Measuring the polarization of electroweak bosons at the LHC allows for important tests of the electroweak-symmetry-breaking mechanism that is realized in nature. Therefore, precise Standard Model predictions are needed for the production of polarized bosons in the presence of realistic kinematic selections. We formulate a method for the calculation of polarized cross-sections at NLO that relies on the pole approximation and the separation of polarized matrix elements at the amplitude level. In this framework, we compute NLO-accurate cross-sections for the production of two polarized Z bosons at the LHC, including for the first time NLO EW corrections and combining them with NLO QCD corrections and contributions from the gluon-induced process.

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31

Denner, Ansgar, Robert Franken, Timo Schmidt et Christopher Schwan. « NLO QCD and EW corrections to vector-boson scattering into W+W− at the LHC ». Journal of High Energy Physics 2022, n^o 6 (juin 2022). http://dx.doi.org/10.1007/jhep06(2022)098.

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Abstract We present the full next-to-leading-order electroweak and QCD corrections to vector-boson scattering into a pair of off-shell opposite-sign W bosons decaying into leptons of different flavour at the LHC. We include full leading-order predictions for the irreducible background. Explicitly, we investigate the process pp → e+νeμ−$$ \overline{\nu} $$ ν ¯ μjj + X at leading orders $$ \mathcal{O} $$ O (α6), $$ \mathcal{O} $$ O (αsα5), $$ \mathcal{O} $$ O ($$ {\alpha}_{\mathrm{s}}^2 $$ α s 2 α4), supplemented by the loop-induced $$ \mathcal{O} $$ O ($$ {\alpha}_{\mathrm{s}}^4 $$ α s 4 α4) contribution, and at next-to-leading orders $$ \mathcal{O} $$ O (α7)and $$ \mathcal{O} $$ O (αsα6) in two setups providing fiducial cross sections as well as differential distributions. We take full account of photon-induced next-to-leading-order contributions, which prove to be non negligible. With −11.4% and −6.7% in the two setups, the electroweak corrections are smaller than for other vector-boson-scattering processes. This can be traced back to the presence of the Higgs-boson resonance in the fiducial phase space, whose effects we analyse within an additional unphysical, but manifestly gauge-invariant setup. The QCD corrections amount to −5.1% and −21.6% in the two setups. The large size of the latter correction, compared to other vector-boson scattering processes, is explained by a very restrictive definition of its fiducial phase space.

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32

Matsedonskyi, Oleksii. « High-temperature electroweak symmetry breaking by SM twins ». Journal of High Energy Physics 2021, n^o 4 (avril 2021). http://dx.doi.org/10.1007/jhep04(2021)036.

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Abstract We analyse a possible adjustment of Twin Higgs models allowing to have broken electroweak (EW) symmetry at all temperatures below the sigma-model scale ∼ 1 TeV. The modification consists of increasing the Yukawa couplings of the twins of light SM fermions. The naturalness considerations then imply a presence of relatively light electroweak-charged fermions, which can be produced at the LHC, and decay into SM gauge and Higgs bosons and missing energy. Analysis of experimental bounds shows that such a modified model features an increased amount of fine-tuning compared to the original Twin Higgs models, but still less tuning than the usual pseudo-Nambu-Goldstone Higgs models not improved by Z2 twin symmetry. The obtained modification in the evolution of the EW symmetry breaking strength can, in particular, have interesting implications for models of EW baryogenesis, which we comment on.

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Obikhod, T. V., et E. A. Petrenko. « INVESTIGATIONS OF ELECTROWEAK SYMMETRY BREAKING MECHANISM FOR HIGGS BOSON DECAYS INTO FOUR FERMIONS ». Problems of Atomic Science and Technology, 21 septembre 2020, 8–12. http://dx.doi.org/10.46813/2020-129-008.

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Models with extended Higgs boson sectors are of prime importance for investigating the mechanism of electroweak symmetry breaking for Higgs decays into four fermions and for Higgs-production in association with a vector bosons. In the framework of the Two-Higgs-Doublet Model using two scenarios obtained from the experimental measurements we presented next-to-leading-order results on the four-fermion decays of light CP-even Higgs boson, h → 4f. With the help of Monte Carlo program Prophecy 4f 3.0, we calculated the values Γ = ΓEW/(ΓEW + ΓSM) and Γ = ΓEW+QCD/(ΓEW+QCD + ΓSM) for Higgs boson decay channels H → νµµeνe, µµee, eeee. We didn’t ﬁnd signiﬁcant diﬀerence when accounting QCD corrections to EW processes in the decay modes of Higgs boson. Using computer programs Pythia 8.2 and FeynHiggs we calculated the following values: σ(V BH)BR(H → ZZ) and σ(V BF)BR(H → WW) for VBF production processes, σ(ggH)BR(H → WW) and σ(ggH)BR(H → ZZ) for gluon fusion production process at 13 and 14 TeV and found good agreement with experimental data.

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34

Frederix, Rikkert, et Ioannis Tsinikos. « Subleading EW corrections and spin-correlation effects in $$t\bar{t}W$$ multi-lepton signatures ». European Physical Journal C 80, n^o 9 (septembre 2020). http://dx.doi.org/10.1140/epjc/s10052-020-8388-6.

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AbstractRecently a slight tension between data and predictions has been reported in $$t\bar{t}W$$ t t ¯ W production by both the CMS and ATLAS collaborations. We revisit the theoretical predictions for this process, focussing on the following two effects. We disentangle various effects that lead to asymmetries among the leptonic decay products of the (anti-)top quarks and W bosons, for which we find that the spin correlations in the top-quark pair are the dominant source. We also discuss the impact of the large, formally subleading, electroweak corrections to $$t\bar{t}W$$ t t ¯ W production at the LHC. We find that this effect changes the $$t\bar{t}W$$ t t ¯ W cross section significantly in the signature phase-space regions, and should therefore be included differentially in the theory to data comparisons.

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35

Pagani, Davide, Ioannis Tsinikos et Eleni Vryonidou. « NLO QCD+EW predictions for tHj and tZj production at the LHC ». Journal of High Energy Physics 2020, n^o 8 (août 2020). http://dx.doi.org/10.1007/jhep08(2020)082.

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Abstract In this work we calculate the cross sections for the hadroproduction of a single top quark or antiquark in association with a Higgs (tHj) or Z boson (tZj) at NLO QCD+EW accuracy. In the case of tZj production we consider both the case of the Z boson undecayed and the complete final state tℓ+ℓ−j, including off-shell and non-resonant effects. We perform our calculation in the five-flavour-scheme (5FS), without selecting any specific production channel (s-, t- or tW associated). Moreover, we provide a more realistic estimate of the theory uncertainty by carefully including the differences between the four-flavour-scheme (4FS) and 5FS predictions. The difficulties underlying this procedure in the presence of EW corrections are discussed in detail. We find that NLO EW corrections are in general within the NLO QCD theory uncertainties only if the flavour scheme uncertainty (4FS vs. 5FS) is taken into account. For the case of tℓ+ℓ−j production we also investigate differences between NLO QCD+EW predictions and NLO QCD predictions matched with a parton shower simulation including multiple photon emissions.

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Costantini, Antonio, Federico De Lillo, Fabio Maltoni, Luca Mantani, Olivier Mattelaer, Richard Ruiz et Xiaoran Zhao. « Vector boson fusion at multi-TeV muon colliders ». Journal of High Energy Physics 2020, n^o 9 (septembre 2020). http://dx.doi.org/10.1007/jhep09(2020)080.

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Abstract High-energy lepton colliders with a centre-of-mass energy in the multi-TeV range are currently considered among the most challenging and far-reaching future accelerator projects. Studies performed so far have mostly focused on the reach for new phenomena in lepton-antilepton annihilation channels. In this work we observe that starting from collider energies of a few TeV, electroweak (EW) vector boson fusion/scattering (VBF) at lepton colliders becomes the dominant production mode for all Standard Model processes relevant to studying the EW sector. In many cases we find that this also holds for new physics. We quantify the size and the growth of VBF cross sections with collider energy for a number of SM and new physics processes. By considering luminosity scenarios achievable at a muon collider, we conclude that such a machine would effectively be a “high-luminosity weak boson collider,” and subsequently offer a wide range of opportunities to precisely measure EW and Higgs couplings as well as discover new particles.

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37

Rana, Narayan. « NNLO EW⊗QCD corrections to on-shell Z production ». SciPost Physics Proceedings, n^o 7 (20 juin 2022). http://dx.doi.org/10.21468/scipostphysproc.7.004.

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In this proceeding, we outline the computational details and present the results for NNLO mixed EW\otimes⊗QCD corrections to on-shell production of Z boson at the LHC. We use the method of differential equation to obtain all the master integrals analytically, appearing in virtual and real-emission contributions. These results increase the accuracy of the predictions and contribute to reduce the theoretical uncertainties.

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Dreyer, Frédéric A., Alexander Karlberg, Jean-Nicolas Lang et Mathieu Pellen. « Precise predictions for double-Higgs production via vector-boson fusion ». European Physical Journal C 80, n^o 11 (novembre 2020). http://dx.doi.org/10.1140/epjc/s10052-020-08610-7.

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AbstractTheoretical predictions with next-to-next-to-leading order (NNLO) QCD accuracy combined with the next-to-leading order (NLO) electroweak (EW) corrections are presented for differential observables of the double-Higgs production process via vector-boson fusion. While the QCD corrections were previously known, the EW ones are computed here for the first time. The numerical results are obtained for a realistic experimental set-up at the LHC and are presented in the form of fiducial cross sections and differential distributions. Within this setup we find that the VBF approximation employed in the NNLO QCD correction is accurate at the sub-percent level. We find that the NLO EW corrections within the fiducial volume are $$-\,6.1\%$$ - 6.1 % , making them of almost the same order as the NLO QCD corrections. In some kinematic regions they can grow as large as $$-\,30\%$$ - 30 % making them the dominant radiative corrections. When the EW corrections are combined with the NNLO QCD corrections we find a total correction of $$-\,14.8\%$$ - 14.8 % . The results presented here thus comprise the state-of-the-art theoretical predicition for the double-Higgs production via vector-boson fusion, which will be of value to the high-luminosity programme at the LHC.

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Lindert, J. M., S. Pozzorini et M. Schönherr. « Precise predictions for V + 2 jet backgrounds in searches for invisible Higgs decays ». Journal of High Energy Physics 2023, n^o 1 (16 janvier 2023). http://dx.doi.org/10.1007/jhep01(2023)070.

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Abstract We present next-to-leading order QCD and electroweak (EW) theory predictions for V + 2 jet production, with V = Z, W±, considering both the QCD and EW production modes and their interference. We focus on phase-space regions where V + 2 jet production is dominated by vector-boson fusion, and where these processes yield the dominant irreducible backgrounds in searches for invisible Higgs boson decays. Predictions at parton level are provided together with detailed prescriptions for their implementation in experimental analyses based on the reweighting of Monte Carlo samples. The key idea is that, exploiting accurate data for W + 2 jet production in combination with a theory-driven extrapolation to the Z + 2 jet process can lead to a determination of the irreducible background at the few-percent level. Particular attention is devoted to the estimate of the residual theoretical uncertainties due to unknown higher-order QCD and EW effects and their correlation between the different V + 2 jet processes, which is key to improve the sensitivity to invisible Higgs decays.

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40

Bonciani, Roberto, Federico Buccioni, Narayan Rana et Alessandro Vicini. « On-shell Z boson production at hadron colliders through 𝒪(ααs) ». Journal of High Energy Physics 2022, n^o 2 (février 2022). http://dx.doi.org/10.1007/jhep02(2022)095.

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Abstract The analytical expressions of the mixed QCD-EW corrections to on-shell Z boson inclusive production cross section at hadron colliders are presented, together with computational details. The results are given in terms of polylogarithmic functions and elliptic integrals. The impact on the prediction of the Z boson production total cross section is discussed, comparing different proton parton density sets.

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Pellen, Mathieu, Rene Poncelet, Andrei Popescu et Timea Vitos. « Angular coefficients in $$\hbox {W}+\hbox {j}$$ production at the LHC with high precision ». European Physical Journal C 82, n^o 8 (10 août 2022). http://dx.doi.org/10.1140/epjc/s10052-022-10641-1.

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AbstractThe extraction of the W-boson mass, a fundamental parameter of the Standard Model, from hadron-hadron collision requires precise theory predictions. In this regard, angular coefficients are crucial to model the dynamics of W-boson production. In this work, we provide, for the first time, angular coefficients at NNLO QCD + NLO EW accuracy for finite transverse momentum W-boson at the LHC. The corrections can reach up to $$10\%$$ 10 % in certain regions of phase space. They are accompanied by a significant reduction of the scale uncertainty. This work should, besides providing reference values for theory-data comparison, provide state-of-the-art theory input for W-boson mass measurements.

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Heinemeyer, S., S. Jadach et J. Reuter. « Theory requirements for SM Higgs and EW precision physics at the FCC-ee ». European Physical Journal Plus 136, n^o 9 (septembre 2021). http://dx.doi.org/10.1140/epjp/s13360-021-01875-1.

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AbstractHigh-precision experimental measurements of the properties of the Higgs boson at $$\sim 125$$ ∼ 125 GeV as well as electroweak precision observables such as the W-boson mass or the effective weak leptonic mixing angle are expected at future $$e^+e^-$$ e + e - colliders such as the FCC-ee. This high anticipated precision has to be matched with theory predictions for the measured quantities at the same level of accuracy. We briefly summarize the status of these predictions within the standard model and of the tools that are used for their determination. We outline how the theory predictions will have to be improved in order to reach the required accuracy, and also comment on the simulation frameworks for the Higgs and EW precision program.

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43

Bonetti, Marco, Erik Panzer, Vladimir A. Smirnov et Lorenzo Tancredi. « Two-loop mixed QCD-EW corrections to gg → Hg ». Journal of High Energy Physics 2020, n^o 11 (novembre 2020). http://dx.doi.org/10.1007/jhep11(2020)045.

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Abstract We compute the two-loop mixed QCD-Electroweak (QCD-EW) corrections to the production of a Higgs boson and a gluon in gluon fusion through a loop of light quarks. The relevant four-point functions with internal massive propagators are expressed as multiple polylogarithms with algebraic arguments. We perform the calculation by integration over Feynman parameters and, independently, by the method of differential equations. We compute the two independent helicity amplitudes for the process and we find that they are both finite. Moreover, we observe a weight drop when all gluons have the same helicity. We also provide a simplified expression for the all-plus helicity amplitude, which is optimised for fast and reliable numerical evaluation in the physical region.

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Bothmann, Enrico, et Davide Napoletano. « Automated evaluation of electroweak Sudakov logarithms in SHERPA ». European Physical Journal C 80, n^o 11 (novembre 2020). http://dx.doi.org/10.1140/epjc/s10052-020-08596-2.

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AbstractWe present an automated implementation for the calculation of one-loop double and single Sudakov logarithms stemming from electroweak radiative corrections within the SHERPA event generation framework, based on the derivation in Denner and Pozzorini (Eur Phys J C 18:461–480, 2001). At high energies, these logarithms constitute the leading contributions to the full NLO electroweak corrections. As examples, we show applications for relevant processes at both the LHC and future hadron colliders, namely on-shell W boson pair production, EW-induced dijet production and electron–positron production in association with four jets, providing the first estimate of EW corrections at this multiplicity.

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Chiesa, Mauro, Carlo Oleari et Emanuele Re. « NLO QCD+NLO EW corrections to diboson production matched to parton shower ». European Physical Journal C 80, n^o 9 (septembre 2020). http://dx.doi.org/10.1140/epjc/s10052-020-8419-3.

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AbstractWe present the matching of NLO QCD and NLO EW corrections to parton showers for vector-boson pair production at the LHC. We consider leptonic final states, including resonant and non-resonant diagrams, spin correlations and off-shell effects. Our results are obtained interfacing the Recola2-Collier one-loop provider with the framework. We discuss our implementation, we validate it at fixed order, and we show our final results matched to parton shower. A by-product of our work is also a general interface between Recola2-Collier and . This is the first time that EW and QCD corrections to diboson production are consistently matched to parton showers.

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46

Le, Duc Ninh, Julien Baglio et Thi Nhung Dao. « Doubly-polarized WZ hadronic production at NLO QCD+EW : calculation method and further results ». European Physical Journal C 82, n^o 12 (7 décembre 2022). http://dx.doi.org/10.1140/epjc/s10052-022-11032-2.

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AbstractThe doubly-polarized production of $$W^\pm Z$$ W ± Z pairs at the Large Hadron Collider (LHC) is presented at next-to-leading order (NLO) accuracy both for the electroweak (EW) and QCD corrections, including a detailed description of the calculational method using the double-pole approximation. Numerical results at the 13 TeV LHC are presented in particular for the $$W^- Z$$ W - Z case in the $$e^-\bar{\nu }_e \mu ^+\mu ^-$$ e - ν ¯ e μ + μ - channel using ATLAS fiducial cuts and for polarized distributions defined in the WZ center-of-mass system. The NLO EW corrections relative to the NLO QCD predictions are found to be smaller than 5% in most kinematic distributions, but can reach the level of 10% in some distributions such as lepton transverse momentum distributions or rapidity separation between the electron and the Z boson. EW corrections are not uniform for different polarizations. A comparison between the new ATLAS measurement of polarization fractions to our theoretical prediction is presented.

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47

Ma, Chichuan, Yuxuan Wang, Xiaofeng Xu, Li Lin Yang et Bin Zhou. « Mixed QCD-EW corrections for Higgs leptonic decay via HW+W− vertex ». Journal of High Energy Physics 2021, n^o 9 (septembre 2021). http://dx.doi.org/10.1007/jhep09(2021)114.

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Abstract We consider the two-loop corrections to the HW+W− vertex at order ααs. We construct a canonical basis for the two-loop integrals using the Baikov representation and the intersection theory. By solving the ϵ-form differential equations, we obtain fully analytic expressions for the master integrals in terms of multiple polylogarithms, which allow fast and accurate numeric evaluation for arbitrary configurations of external momenta. We apply our analytic results to the decay process H → νeeW, and study both the integrated and differential decay rates. Our results can also be applied to the Higgs production process via W boson fusion.

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48

Chen, Lisong, et Ayres Freitas. « Mixed EW-QCD leading fermionic three-loop corrections at $$ \mathcal{O} $$(αsα2) to electroweak precision observables ». Journal of High Energy Physics 2021, n^o 3 (mars 2021). http://dx.doi.org/10.1007/jhep03(2021)215.

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Abstract 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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Huang, Xu-Dong, Xing-Gang Wu, Xu-Chang Zheng, Qing Yu, Sheng-Quan Wang et Jian-Ming Shen. « Z-boson hadronic decay width up to $${{\mathcal {O}}}(\alpha _s^4)$$-order QCD corrections using the single-scale approach of the principle of maximum conformality ». European Physical Journal C 81, n^o 4 (avril 2021). http://dx.doi.org/10.1140/epjc/s10052-021-09092-x.

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AbstractIn the paper, we study the properties of the Z-boson hadronic decay width by using the $$\mathcal {O}(\alpha _s^4)$$ O ( α s 4 ) -order quantum chromodynamics (QCD) corrections with the help of the principle of maximum conformality (PMC). By using the PMC single-scale approach, we obtain an accurate renormalization scale-and-scheme independent perturbative QCD (pQCD) correction for the Z-boson hadronic decay width, which is independent to any choice of renormalization scale. After applying the PMC, a more convergent pQCD series has been obtained; and the contributions from the unknown $$\mathcal {O}(\alpha _s^5)$$ O ( α s 5 ) -order terms are highly suppressed, e.g. conservatively, we have $$\Delta \Gamma _{\mathrm{Z}}^{\mathrm{had}}|^{{{\mathcal {O}}}(\alpha _s^5)}_{\mathrm{PMC}}\simeq \pm 0.004$$ Δ Γ Z had | PMC O ( α s 5 ) ≃ ± 0.004 MeV. In combination with the known electro-weak (EW) corrections, QED corrections, EW–QCD mixed corrections, and QED–QCD mixed corrections, our final prediction of the hadronic Z decay width is $$\Gamma _{\mathrm{Z}}^{\mathrm{had}}=1744.439^{+1.390}_{-1.433}$$ Γ Z had = 1744 . 439 - 1.433 + 1.390 MeV, which agrees with the PDG global fit of experimental measurements, $$1744.4\pm 2.0$$ 1744.4 ± 2.0 MeV.

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Bagnaschi, Emanuele, Giuseppe Degrassi, Sebastian Paßehr et Pietro Slavich. « Full two-loop QCD corrections to the Higgs mass in the MSSM with heavy superpartners ». European Physical Journal C 79, n^o 11 (novembre 2019). http://dx.doi.org/10.1140/epjc/s10052-019-7417-9.

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Abstract We improve the determination of the Higgs-boson mass in the MSSM with heavy superpartners, by computing the two-loop threshold corrections to the quartic Higgs coupling that involve both the strong and the electroweak gauge couplings. Combined with earlier results, this completes the calculation of the two-loop QCD corrections to the quartic coupling at the SUSY scale. We also compare different computations of the relation between the quartic coupling and the pole mass of the Higgs boson at the EW scale. We find that the numerical impact of the new corrections on the prediction for the Higgs mass is modest, but comparable to the accuracy of the Higgs-mass measurement at the LHC.

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