Effects of heavy Majorana neutrinos on lepton flavor violating processes

Hernández-Tomé, G.; Illana, José I.; Masip, M.; Castro, G. López; Roig, Pablo

doi:10.1103/physrevd.101.075020

“…We have checked that in the limit where there are no charged-scalar contributions, i.e., for a scalar sector matching the SM one, our results are in agreement with refs [67,154]. (see also[22,26,170]). …”

supporting

confidence: 87%

Minimal inverse-seesaw mechanism with Abelian flavour symmetries

Câmara

¹

,

Felipe

²

,

Joaquim

³

2021

J. High Energ. Phys.

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We study the phenomenology of the minimal (2, 2) inverse-seesaw model supplemented with Abelian flavour symmetries. To ensure maximal predictability, we establish the most restrictive flavour patterns which can be realised by those symmetries. This setup requires adding an extra scalar doublet and two complex scalar singlets to the Standard Model, paving the way to implement spontaneous CP violation. It is shown that such CP-violating effects can be successfully communicated to the lepton sector through couplings of the scalar singlets to the new sterile fermions. The Majorana and Dirac CP phases turn out to be related, and the active-sterile neutrino mixing is determined by the active neutrino masses, mixing angles and CP phases. We investigate the constraints imposed on the model by the current experimental limits on lepton flavour-violating decays, especially those on the branching ratio BR(μ → eγ) and the capture rate CR(μ − e, Au). The prospects to further test the framework put forward in this work are also discussed in view of the projected sensitivities of future experimental searches sensitive to the presence of heavy sterile neutrinos. Namely, we investigate at which extent upcoming searches for μ → eγ, μ → 3e and μ − e conversion in nuclei will be able to test our model, and how complementary will future high-energy collider and beam-dump experiments be in that task.

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“…Taking this into account, our results reproduce those in refs. [50,52,73]. It is also worth to mention that the O(M 2 Z ) terms are clearly negligible for the G h and H h functions.…”

Section: Z → Decaysmentioning

confidence: 93%

“…Within the LHT, it was shown recently [45] that the inverse see-saw of type I [47][48][49] is able to reproduce current data preserving the T symmetry. It is well known that the heavy Majorana masses thus introduced (in the 10 TeV scale) impact lepton flavor violating (LFV) processes [50][51][52]. Here we consider these effects in the following LFV processes: → γ decays (which were first addressed in this context in ref.…”

Section: Jhep02(2022)054mentioning

confidence: 99%

Lepton flavor violation in the Littlest Higgs Model with T parity realizing an inverse seesaw

Pacheco

¹

,

Roig

²

2022

J. High Energ. Phys.

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We study lepton flavor violation (LFV) within the Littlest Higgs Model with T parity (LHT) realizing an inverse seesaw (ISS) mechanism of type I. With respect to the traditional LHT, there appear new 𝒪(10 TeV) Majorana neutrinos, driving LFV. For τ →$$ \mathrm{\ell \ell}^{\prime}\overline{\mathrm{\ell}}^{{\prime\prime} } $$ ℓℓ ′ ℓ ¯ ″ (including wrong-sign, ℓ = e, μ) decays and μ → e conversion in Ti, we get typical rates only one order of magnitude below present bounds (ℓ → ℓ′γ can reach the current upper limit) and for Z →$$ \overline{\tau}\mathrm{\ell } $$ τ ¯ ℓ , μ →$$ ee\overline{e} $$ ee e ¯ and conversion in Au, results are within two orders of magnitude from present limits. Correlations among modes are drastically different to the traditional LHT and other models, which would ease the confrontation of this scenario to eventual measurements of LFV processes involving charged leptons.

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“…In this article we will employ the SMEFT framework to study low-energy constraints on LFVZD. This type of decays have been also studied within several UV-complete models, such as heavy sterile neutrinos [39][40][41][42][43][44][45], supersymmetry [22,46], leptoquarks [47], or in scenarios with extended gauge sectors [48][49][50][51]. They have also been previously explored in the context of SMEFT in [16,24,25,28,33].…”

Section: Introductionmentioning

confidence: 99%

Z lepton flavour violation as a probe for new physics at future $$e^+e^-$$ colliders

Marcano

¹

,

Roy

²

2021

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In this work we assess the potential of discovering new physics by searching for lepton-flavour-violating (LFV) decays of the Z boson, $$Z\rightarrow \ell _i \ell _j$$ Z → ℓ i ℓ j , at the proposed circular $$e^+e^-$$ e + e - colliders CEPC and FCC-ee. Both projects plan to run at the Z-pole as a “Tera Z factory”, i.e., collecting $${\mathcal {O}}\left( 10^{12} \right) $$ O 10 12 Z decays. In order to discuss the discovery potential in a model-independent way, we revisit the LFV Z decays in the context of the Standard Model effective field theory and study the indirect constraints from LFV $$\mu $$ μ and $$\tau $$ τ decays on the operators that can induce $$Z\rightarrow \ell _i \ell _j$$ Z → ℓ i ℓ j . We find that, while the $$Z\rightarrow \mu e$$ Z → μ e rates are beyond the expected sensitivities, a Tera Z factory is promising for $$Z\rightarrow \tau \ell $$ Z → τ ℓ decays, probing New Physics at the same level of future low-energy LFV observables.

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Effects of heavy Majorana neutrinos on lepton flavor violating processes

Cited by 31 publications

References 110 publications

Minimal inverse-seesaw mechanism with Abelian flavour symmetries

Minimal inverse-seesaw mechanism with Abelian flavour symmetries

Lepton flavor violation in the Littlest Higgs Model with T parity realizing an inverse seesaw

Z lepton flavour violation as a probe for new physics at future $$e^+e^-$$ colliders

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