Search for top quark FCNC couplings in Z′ models at the LHC and CLIC

Çakır, O.; Cakir, I. Türk; Şenol, A.; Tasci, A. T.

doi:10.1140/epjc/s10052-010-1474-4

Cited by 12 publications

(3 citation statements)

References 29 publications

(38 reference statements)

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“…As for models with FCNC mediated by a new neutral gauge boson, which we generically have denoted by Z , they have been widely studied in the literature [64,65]. In Table 1 we present a summary of some of the more popular models that predict a new Z gauge boson.…”

Section: Trilinear Neutral Gauge Boson Couplingsmentioning

confidence: 99%

Contributions to $$ZZV^*$$ ($$V=\gamma ,Z,Z'$$) couplings from CP violating flavor changing couplings

2021

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The one-loop contributions to the trilinear neutral gauge boson couplings $$ZZV^*$$ Z Z V ∗ ($$V=\gamma ,Z,Z'$$ V = γ , Z , Z ′ ), parametrized in terms of one CP-conserving $$f_5^{V}$$ f 5 V and one CP-violating $$f_4^{V}$$ f 4 V form factors, are calculated in models with CP-violating flavor changing neutral current couplings mediated by the Z gauge boson and an extra neutral gauge boson $$Z'$$ Z ′ . Analytical results are presented in terms of Passarino-Veltman scalar functions. Constraints on the vector and axial couplings of the Z gauge boson $$\left| g_{{VZ}}^{tu}\right| < 0.0096$$ g VZ tu < 0.0096 and $$\left| g_{{VZ}}^{tc}\right| <0.011$$ g VZ tc < 0.011 are obtained from the current experimental data on the $$t\rightarrow Z q$$ t → Z q decays. It is found that in the case of the $$ZZ\gamma ^*$$ Z Z γ ∗ vertex the only non-vanishing form factor is $$f_5^{\gamma }$$ f 5 γ , which can be of the order of $$10^{-3}$$ 10 - 3 , whereas for the $$ZZZ^*$$ Z Z Z ∗ vertex both form factors $$f_5^{Z}$$ f 5 Z and $$f_4^{Z}$$ f 4 Z are non-vanishing and can be of the order of $$10^{-6}$$ 10 - 6 and $$10^{-5}$$ 10 - 5 , respectively. Our estimates for $$f_5^{\gamma }$$ f 5 γ and $$f_5^{Z}$$ f 5 Z are smaller than those predicted by the standard model, where $$f_4^{Z}$$ f 4 Z is absent up to the one loop level. We also estimate the $$ZZ{Z'}^{*}$$ Z Z Z ′ ∗ form factors arising from both diagonal and non-diagonal $$Z'$$ Z ′ couplings within a few extension models. It is found that in the diagonal case $$f_{5}^{Z'}$$ f 5 Z ′ is the only non-vanishing form factor and its real and imaginary parts can be of the order of $$10^{-1}$$ 10 - 1 –$$10^{-2}$$ 10 - 2 and $$ 10^{-2}$$ 10 - 2 –$$10^{-3}$$ 10 - 3 , respectively, with the dominant contributions arising from the light quarks and leptons. In the non-diagonal case $$f_{5}^{Z^\prime }$$ f 5 Z ′ can be of the order of $$10^{-4}$$ 10 - 4 , whereas $$f_4^{Z'}$$ f 4 Z ′ can reach values as large as $$10^{-7}$$ 10 - 7 –$$10^{-8}$$ 10 - 8 , with the largest contributions arising from the $$Z'tq$$ Z ′ t q couplings.

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Section: Trilinear Neutral Gauge Boson Couplingsmentioning

confidence: 99%

Contributions to $$ZZV^*$$ ($$V=\gamma ,Z,Z'$$) couplings from CP violating flavor changing couplings

2021

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“…The production of a top quark in association with a charm quark at the LHC and the CLIC electron-positron collider via a Z flavor changing in the s-channel have been studied in Refs. [21,24] and the discovery regions of the new model parameter space have been presented. In addition to the production mechanisms to probe the properties of the new flavor changing mediators, such model's parameter space could be also probed by looking at the top quark decays.…”

Section: Theoretical Formalismmentioning

confidence: 99%

“…The flavor changing Z has been also expected in theories with dynamical symmetry breaking approach. The top quark flavor changing have already been studied in many papers in the context of non-universality, where the strength of the couplings are different among different generations [21][22][23][24][25][26][27][28][29][30][31][32][33]. There are also beyond the SM theories where the flavor changing could proceed through color sextet vector and scalar bosons [34,35].…”

Section: Introductionmentioning

confidence: 99%

Same-sign top pair plus W production in flavor changing vector and scalar models

et al. 2018

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We investigate the prospect of the LHC for discovering new physics effects via new strategies in the same-sign top pair and same-sign top pair associated with a W boson signatures. Significant enhancement in production of same-sign top quarks (plus a W boson) is a joint property of several models beyond the standard model. We concentrate on the leptonic (electron and muon) decay of the top quarks and study the exclusion reach of the LHC data for a simplified model approach where top quark flavor changing could occur through a Z or a neutral scalar φ exchange. Less background contributions and clean signature are the advantages of the leptonic decay mode of the top quarks in the same-sign production processes. A combination is performed on both same-sign top pair and same-sign top pair plus a W boson production modes which enables us to reach a large fraction of the model parameter space. Assuming the couplings of new physics of the order of 10 −2 , the mass of a flavor changing Z or a neutral scalar above 1 TeV could be excluded. We propose a momentum dependent charge asymmetry and angular observables in the same-sign top process which provide the possibility of separation of new physics signal from the SM backgrounds as well as discrimination of the flavor changing tuX from tcX, where X = Z , φ.

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Flavor changing neutral currents and a Z′

Valencia¹

2013

SSP 2012

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Search for top quark FCNC couplings in Z′ models at the LHC and CLIC

Cited by 12 publications

References 29 publications

Contributions to $$ZZV^*$$ ($$V=\gamma ,Z,Z'$$) couplings from CP violating flavor changing couplings

Contributions to $$ZZV^*$$ ($$V=\gamma ,Z,Z'$$) couplings from CP violating flavor changing couplings

Same-sign top pair plus W production in flavor changing vector and scalar models

Flavor changing neutral currents and a Z′

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