Scotogenic top-quark FCNC decays

Chen, Chuan-Hung; Nomura, Takaaki

doi:10.1103/physrevd.106.095005

Cited by 4 publications

(3 citation statements)

References 43 publications

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“…In terms of the chiral structures of the initial-and final-state quarks, the effective interactions for t → q(h, γ, Z) can be parametrized as [28]:…”

Section: Top-fcnc Processesmentioning

confidence: 99%

“…Thus, if any signal in these processes is detected in experiments, it definitely indicates new physics effects at play. Some interesting extensions of the SM proposed to enhance the top-FCNC decays can be found in [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28].…”

Section: Introductionmentioning

confidence: 99%

“…Thus, the new mediating particles running in the loop diagrams should be Z 2 -odd scalar bosons and fermions. It is found that a minimal extension to the SM can include one inert Higgs doublet [85], one charged Higgs singlet [86], one SU 2 L ( ) -singlet vector-like quark [28], and two singlet vector-like Dirac-type neutral leptons [87], where the Z 2 -odd quark is responsible for the top-FCNC processes, and the Z 2 -odd singlet leptons are for the rare lepton flavor-conserving and -violating processes.…”

Section: Introductionmentioning

confidence: 99%

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Top-quark FCNC decays, LFVs, lepton g − 2, and W mass anomaly with inert charged Higgses

Chen,

Chiang,

2024

J. Phys. G: Nucl. Part. Phys.

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The observed flavor-changing neutral-current (FCNC) processes in the standard model (SM) arise from the loop diagrams involving the weak charged currents mediated by the W-gauge boson. Nevertheless, the top-quark FCNCs and lepton flavor-violating processes resulting from the same mechanism are highly suppressed. We investigate possible new physics effects that can enhance the suppressed FCNC processes, such as a top quark decaying into a light quark with a Higgs or gauge boson in the final state, i.e. t → q(h, V) with V = γ, Z, g, h → ℓ ℓ ′ , and ℓ → ℓ ′ γ . To achieve the assumption that the induced FCNCs are all from quantum loops, we consider the scotogenic mechanism, where a Z 2 symmetry is introduced and only new particles carry an odd Z 2 parity. With the extension of the SM to include an inert Higgs doublet, an inert charged Higgs singlet, a vector-like singlet quark, and two neutral leptons, it is found that, with relevant constraints taken into account, the t → c(h, Z), h → μ τ, and τ → ℓ γ decays can be enhanced up to the expected sensitivities in experiments. The branching ratios of h → μ + μ −/τ + τ − from only new physics effects can reach up to O ( 10 − 3 ) . Intriguingly, the resulting muon g − 2 can fit the combined data within 2 standard deviations, whereas the electron g − 2 can have either sign with a magnitude of O ( 10 − 13 − 10 − 12 ) . In addition, we examine the oblique parameters in the model and find that the resulting W-mass anomaly observed by CDF II can be accommodated.

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“…In terms of the chiral structures of the initial-and final-state quarks, the effective interactions for t → q(h, γ, Z) can be parametrized as [28]:…”

Section: Top-fcnc Processesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Top-quark FCNC decays, LFVs, lepton g − 2, and W mass anomaly with inert charged Higgses

Chen,

Chiang,

2024

J. Phys. G: Nucl. Part. Phys.

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Top quark flavor changing neutral currents at Future Linear Colliders

Jueid,

Kanemura

2024

EPJ Web Conf.

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We discuss the production and the decay of top quark through flavor-changing neutral current (FCNC) interaction at future linear colliders. We first discuss the theoretical predictions of top quark FCNC decays into qH and qZ within a class of t–channel simplified dark matter models. For the existing bounds on the top quark FCNC interactions at the Large Hadron Collider, we estimate the production rates of top quark through FCNC interactions at future linear colliders for energies from 250 GeV to 3 TeV.

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Dark matter as the trigger of flavor changing neutral current decays of the top quark

Jueid,

Kanemura

2024

Phys. Rev. D

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We suggest a simplified model that simultaneously addresses the dark matter problem and gives rise to top-quark flavor changing neutral current (FCNC) interactions at the one-loop order. The model consists of two extra SU(2)L gauge singlets: a colored mediator of spin zero (S) and a right-handed fermion (χ); both are odd under an Z2 symmetry. The right-handed fermion plays the role of the dark matter candidate. In this model, the presence of the two dark sector particles generates one-loop induced FCNC decays of the top quark into light quarks and bosons such as the gluon, the photon, the Z boson, or the Higgs boson. As a case study, we analyze the top-quark FCNC decays into light quarks (u or c) and Z or Higgs bosons. We then study the reliable solutions to the dark matter problem by estimating the regions in the parameter space that are consistent with the measurement of the dark matter relic density. We also revisit the bounds from the searches of dark matter in events with at least one high-pT jet and large missing transverse energy at the Large Hadron Collider (LHC). We then define four benchmark points that are consistent with the existing constraints from collider experiments and cosmology. We finally estimate, for these benchmark scenarios, the rates of a broad range of channels that can be used to probe the connection between the top FCNC transitions and dark matter, both at the HL-LHC and at a future 100 TeV collider. Published by the American Physical Society 2024

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Scotogenic top-quark FCNC decays

Cited by 4 publications

References 43 publications

Top-quark FCNC decays, LFVs, lepton g − 2, and W mass anomaly with inert charged Higgses

Top-quark FCNC decays, LFVs, lepton g − 2, and W mass anomaly with inert charged Higgses

Top quark flavor changing neutral currents at Future Linear Colliders

Dark matter as the trigger of flavor changing neutral current decays of the top quark

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