Neutrino tridents and W - Z interference

We propose a one-loop induced radiative neutrino mass model with anomaly free flavour dependent gauge symmetry: µ minus τ symmetry U(1) µ−τ . A neutrino mass matrix satisfying current experimental data can be obtained by introducing a weak isospin singlet scalar boson that breaks U(1) µ−τ symmetry, an inert doublet scalar field, and three right-handed neutrinos in addition to the fields in the standard model. We find that a characteristic structure appears in the neutrino mass matrix: two-zero texture form which predicts three non-zero neutrino masses and three non-zero CP-phases from five well measured experimental inputs of two squared mass differences and three mixing angles. Furthermore, it is clarified that only the inverted mass hierarchy is allowed in our model. In a favored parameter set from the neutrino sector, the discrepancy in the muon anomalous magnetic moment between the experimental data and the the standard model prediction can be explained by the additional neutral gauge boson loop contribution with mass of order 100 MeV and new gauge coupling of order 10 −3 .

Section: Muon Anomalous Magnetic Moment and Lepton Flavour Violationsupporting

confidence: 72%

Flavour dependent gauged radiative neutrino mass model

Baek¹,

Okada²,

Yagyu

2015

“…In the case of gauged lepton number, one simultaneously also generates couplings to the corresponding neutrinos. In the latter case, strong constraints on the coupling to muons, g µ , can be derived from the measured rate of neutrino trident production [51,52]. The bound is at the level of g µ 10 −3 and is shown in the left panel of figure 7.…”

Section: Jhep03(2018)188mentioning

confidence: 99%

“…In the right panel, we consider the case in of the muon and the electron are indirect constraints from having V in the loop, while the constraints from BaBar [31] and NA64 [55,56] come from direct decays to electrons. On the left panel, the constraint from ν-trident production based on measurements by the CCFR collaboration [52] assumes that the V couples with equal strength to the left-handed muon and muon neutrino [51], i.e., to the SU(2) doublet L µ . This constraint does not apply to models in which V does not couple to neutrinos, i.e., dark-photon models.…”

Section: Jhep03(2018)188mentioning

confidence: 99%

Light resonances and the low-q2 bin of $$ {R}_{K^{*}} $$

Altmannshofer

Harnik

Baker

et al. 2018

LHCb has reported hints of lepton-flavor universality violation in the rare decays B → K ( * ) + − , both in high-and low-q 2 bins. Although the high-q 2 hint may be explained by new short-ranged interactions, the low-q 2 one cannot. We thus explore the possibility that the latter is explained by a new light resonance. We find that LHCb's central value of R K * in the low-q 2 bin is achievable in a restricted parameter space of new-physics scenarios in which the new, light resonance decays preferentially to electrons and has a mass within approximately 10 MeV of the di-muon threshold. Interestingly, such an explanation can have a kinematic origin and does not require a source of lepton-flavor universality violation. A model-independent prediction is a narrow peak in the differential B → K * e + e − rate close to the di-muon threshold. If such a peak is observed, other observables, such as the differential B → Ke + e − rate and R K , may be employed to distinguish between models. However, if a low-mass resonance is not observed and the low-q 2 anomaly increases in significance, then the case for an experimental origin of the lepton-flavor universality violating anomalies would be strengthened. To further explore this, we also point out that, in analogy to J/ψ decays, e + e − and µ + µ − decays of φ mesons can be used as a cross check of lepton-flavor universality by LHCb with 5 fb −1 of integrated luminosity.

“…As mentioned in the Introduction, although a O(100 MeV) Z µτ is allowed, its coupling strength (g µτ ) is strongly constrained to be less than ∼ 10 −3 from the measurement of neutrino trident cross section by experiments like CHARM-II [94] and CCFR [95]. In our analysis, we find that for M Zµτ = 100 MeV and g µτ = 9 × 10 −4 the value of ∆a µ = 22.6 × 10 −10 , which lies around the ballpark value given in eq.…”

Section: Muon (G − 2)mentioning

confidence: 99%

Neutrino mass, dark matter and anomalous magnetic moment of muon in a U 1 L μ − L τ $$ \mathrm{U}{(1)}_L{{}_{{}_{\mu}}}_{-}{{}_L}_{{}_{\tau }} $$ model

Biswas

Choubey

Khan

2016

The observation of neutrino masses, mixing and the existence of dark matter are amongst the most important signatures of physics beyond the Standard Model (SM). In this paper, we propose to extend the SM by a local L µ −L τ gauge symmetry, two additional complex scalars and three right-handed neutrinos. The L µ − L τ gauge symmetry is broken spontaneously when one of the scalars acquires a vacuum expectation value. The L µ − L τ gauge symmetry is known to be anomaly free and can explain the beyond SM measurement of the anomalous muon (g − 2) through additional contribution arising from the extra Z µτ mediated diagram. Small neutrino masses are explained naturally through the Type-I seesaw mechanism, while the mixing angles are predicted to be in their observed ranges due to the broken L µ − L τ symmetry. The second complex scalar is shown to be stable and becomes the dark matter candidate in our model. We show that while the Z µτ portal is ineffective for the parameters needed to explain the anomalous muon (g − 2) data, the correct dark matter relic abundance can easily be obtained from annihilation through the Higgs portal. Annihilation of the scalar dark matter in our model can also explain the Galactic Centre gamma ray excess observed by Fermi-LAT. We show the predictions of our model for future direct detection experiments and neutrino oscillation experiments.