Asymptotic states and renormalization in Lorentz-violating quantum field theory

Cambiaso, M.; Lehnert, Ralf; Potting, Robertus

doi:10.1103/physrevd.90.065003

Cited by 60 publications

(38 citation statements)

References 127 publications

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“…At leading order, each contribution from Lorentz violation arises as an insertion on a propagator or a vertex. The matrix element for a Lorentz-violating process can then be computed from the Feynman diagrams in the usual way, except perhaps for some technical issues involving external legs [14]. However, only a subset of the Lorentzviolating insertions lead to physically observable effects.…”

Section: B Observablesmentioning

confidence: 99%

Lorentz andCPTviolation in top-quark production and decay

2016

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The prospects are explored for testing Lorentz and CPT symmetry in the top-quark sector. We present the relevant Lagrange density, discuss physical observables, and describe the signals to be sought in experiments. For top-antitop pair production via quark or gluon fusion with subsequent semileptonic or hadronic decays, we obtain the matrix element in the presence of Lorentz violation using the narrow-width approximation. The issue of testing CPT symmetry in the top-quark sector is also addressed. We demonstrate that single-top production and decay is well suited to a search for CPT violation, and we present the matrix elements for single-top production in each of the four tree-level channels. Our results are applicable to searches for Lorentz violation and studies of CPT symmetry in collider experiments, including notably high-statistics top-antitop and single-top production at the Large Hadron Collider.

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Section: B Observablesmentioning

confidence: 99%

Lorentz andCPTviolation in top-quark production and decay

2016

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“…To see this, consider the forward spin-averaged elastic-scattering matrix element M of a virtual photon of momentum q scattering from a free massless SME quark of momentum k with flavor f . Using the sum over fermion spins, we find this is given by [78,82]…”

Section: Minimal C-type Coefficientsmentioning

confidence: 99%

Lorentz and CPT violation in partons

Kostelecký

Lunghi

Sherrill

et al. 2020

J. High Energ. Phys.

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A framework is presented for the factorization of high-energy hadronic processes in the presence of Lorentz and CPT violation. The comprehensive effective field theory describing Lorentz and CPT violation, the Standard-Model Extension, is used to demonstrate factorization of the hadronic tensor at leading order in electroweak interactions for deep inelastic scattering and for the Drell-Yan process. Effects controlled by both minimal and nonminimal coefficients for Lorentz violation are explored, and the equivalent parton-model description is derived. The methodology is illustrated by determining cross sections and studying estimated attainable sensitivities to Lorentz violation using real data collected at the Hadronen-Elektronen Ring Anlage and the Large Hadron Collider and simulated data for the future US-based electron-ion collider.√ 2 (γ 0 + γ 3 ), γ i ⊥ = γ 1 , γ 2 . The ellipses

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“…As it is discussed in Ref., 106 these modifications lead to nontrivial changes in the Lehmann-Symanzik-Zimmermann (LSZ) reduction formalism. In this scenario, dispersion relations can be altered significantly by allowing the occurrence of some processes forbidden in the standard theory.…”

Section: -90mentioning

confidence: 99%

“…In this scenario, dispersion relations can be altered significantly by allowing the occurrence of some processes forbidden in the standard theory. 106 In the case at hand, the complete propagator of the fermion f that results from the incorporation of the anomalous CP T -odd bilinear term has already been calculated and used in radiative corrections. [88][89][90] The use of this exact propagator may induce the decay of the Z boson into a pair of top quarks, which would show up through an imaginary contribution to the loop amplitudes characterizing the Z → γγ and Z → gg transitions.…”

Section: -90mentioning

confidence: 99%

Decays Z → γγ and Z → gg in the Standard Model Extension

Castro-Medina

Novales‐Sánchez

Toscano

et al. 2015

Int. J. Mod. Phys. A

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The Z → γγ and Z → gg decays are studied in the context of the renormalizable version of the Standard Model Extension. The CP T -oddψγ 5 / bψ bilinear interaction, which involves the constant background field bα and which has been a subject of interest in literature, is considered. It is shown that the Z → γγ and Z → gg decays, which are strictly zero in the standard model, can be generated radiatively at the one-loop level. It is found that these decays are gauge invariant and free of ultraviolet divergences, and that the corresponding decay widths only depend on the spatial component of the background field b. IntroductionThe trilinear V V V (V = γ, Z) and quartic V V V V neutral couplings are quite suppressed, as they first arise at the one-loop level a in the Standard Model (SM) and in most of its renormalizable extensions. Since new physics effects could be more apparent in those processes which are quite suppressed or forbidden in the SM, these couplings constitute a good mechanism for investigating possible signals of physics beyond the Fermi scale. The charged counterparts W W V and W W V V , of these neutral couplings, arise at the tree level and are related by gauge invariance in the sense that they are simultaneously induced by1, 2 However, this type of gauge connection does not exist between the V V V and V V V V couplings.3, 4 While the V V V V couplings receive one-loop contributions from both fermionic and bosonic particles b , the V V V ones are exclusively generated by fermionic triangles.38-40 Intimately related with the absence of a gauge link between the V V V and V V V V couplings is the fact that none of the V V V vertices reflects the non-Abelian nature of the electroweak group, as the Yang-Mills sector neither induces these couplings at the tree-level nor contribute to them at the one-loop order. This is in contrast with the quartic V V V V couplings, which are generated by the Yang-Mills sector at the one-loop level.5-37 The trilinear V V V couplings are indeed severely restricted by the Bose and Lorentz symmetries. It turns out that if both Bose symmetry and Lorentz invariance are simultaneously respected, the V V V coupling vanishes when the three bosons are real, though they can exist when at least one of the particles is off-shell.38-40 As a consequence, the Z → γγ decay is forbidden. This result is known as the Landau-Yang's theorem, 41,42 which establishes that a vector particle cannot decay into two massless vector particles. This means that the Z decay into two gluons is also forbidden c . This theorem invokes Bose symmetry and rotational invariance arguments. Nevertheless, as soon as this requirement is relaxed, the V V V vertex with the three bosons on-shell can exist. In particular, the rare decays of the Z gauge boson Z → γγ and Z → gg are allowed.In this paper, we are interested in studying the decays Z → γγ and Z → gg in the context of the minimal Lorentz-and CP T -violating Standard Model Extension 45,46 (SME), which is a renormalizable extension of the SM that incorporat...

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Asymptotic states and renormalization in Lorentz-violating quantum field theory

Cited by 60 publications

References 127 publications

Lorentz andCPTviolation in top-quark production and decay

Lorentz andCPTviolation in top-quark production and decay

Lorentz and CPT violation in partons

Decays Z → γγ and Z → gg in the Standard Model Extension

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