Detecting the 
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 gauge boson at Belle II

We study the structure of the neutrino-mass matrix in the minimal gauged U(1) L μ −L τ model, where three right-handed neutrinos are added to the Standard Model in order to obtain non-zero masses for the active neutrinos. Because of the U(1) L μ −L τ gauge symmetry, the structure of both Dirac and Majorana mass terms of neutrinos is tightly restricted. In particular, the inverse of the neutrinomass matrix has zeros in the (μ, μ) and (τ, τ ) components, namely, this model offers a symmetric realization of the socalled two-zero-minor structure in the neutrino-mass matrix. Due to these constraints, all the CP phases -the Dirac CP phase δ and the Majorana CP phases α 2 and α 3 -as well as the mass eigenvalues of the light neutrinos m i are uniquely determined as functions of the neutrino mixing angles θ 12 , θ 23 , and θ 13 , and the squared mass differences m 2 21 and m 2 31 . We find that this model predicts the Dirac CP phase δ to be δ 1.59π -1.70π (1.54π -1.78π ), the sum of the neutrino masses to be i m i 0.14-0.22 eV (0.12-0.40 eV), and the effective mass for the neutrinoless double-beta decay to be m ββ 0.024-0.055 eV (0.017-0.12 eV) at 1σ (2σ ) level, which are totally consistent with the current experimental limits. These predictions can soon be tested in future neutrino experiments. Implications for leptogenesis are also discussed.

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“…For other recent studies on gauged U(1) L μ −L τ models, see Refs. [23][24][25][26][27][28][29][30][31][32][33][34][35].…”

Section: Introductionmentioning

confidence: 99%

Predictions for the neutrino parameters in the minimal gauged $$\hbox {U}(1)_{L_\mu -L_\tau }$$ U ( 1 ) L μ - L τ model

2017

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“…where the current measurement is ∆a µ = a exp µ − a SM µ = (28.7 ± 8.0) × 10 −10 [37], the Z ′ contribution is given as [29]:…”

Section: Numerical Analysis and Discussionmentioning

confidence: 99%

“…Influence on e + e − → γZ ′ Next, we examine the influence of vector-like leptons on the e + e − → γZ ′ process, which arises from the kinetic mixing [29]. The Feynman diagram for the loop-induced kinetic mixing is sketched in Fig.…”

Section: B Z ′ and Rare τ Decaysmentioning

confidence: 99%

“…7, where the relation of E γ and q 2 is given Table III, where g Z ′ = 10 −3 is fixed and the integrated luminosity of 50 ab −1 is used in the numerical calculations; here we applied formulas for the signal and SM background cross section in Ref. [29]. It can be found that the significance can be over 3σ as m Z ′ 1.0 GeV and is increased(decreased) for Number of signal events N S and corresponding significance, defined by N S 14 (11) 19 (14) 23 (17) 11 (9) 9 (8 Two heavy vector-like leptons τ ′ and τ ′′ are introduced to generate the LFV scalar decays in this paper; therefore, it is of interest to study the production of the heavy leptons at the LHC.…”

Section: B Z ′ and Rare τ Decaysmentioning

confidence: 99%

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Lμ−Lτ gauge-boson production from lepton flavor violating τ decays at Belle II

Chen

Nomura²

2017

Phys. Rev. D

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L µ − L τ gauge boson (Z ′ ) with a mass in the MeV to GeV region can resolve not only the muon g − 2 excess, but also the gap in the high-energy cosmic neutrino spectrum at IceCube. It was recently proposed that such a light gauge boson can be detected during the Belle II experiment with a luminosity of 50 ab −1 by the e + e − → γ + / E process through the kinetic mixing with the photon, where the missing energy / E is from the Z ′ →νν decays. We study the phenomenological implications when a pair of singlet vector-like leptons carrying different L µ − L τ charges are included, and a complex singlet scalar (φ S ) is introduced to accomplish the spontaneous U (1) Lµ−Lτ symmetry breaking. It is found that the extension leads to several phenomena of interest, including (i) branching ratio (BR) for h → µτ can be of the order of 10 −3 ; (ii) φ S -mediated muon g − 2 can be of the order of 10 × 10 −10 ; (iii) BR for τ → µφ * S → µZ ′ Z ′ can be 10 −8 , and (iv) kinetic mixing between the Z ′ boson and photon is sensitive to the relative heavy lepton masses. The predicted BRs for τ → (3µ + / E, 5µ) through the leptonic Z ′ decays can reach a level of 10 −9 , in which the results fall within the sensitivity of the Belle II in the search for the rare tau decays.

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“…Both of these marginal operators have been studied autonomously at electron colliders in the hidden photon context [5][6][7][8][9][10][11][12][13][14][15][16][17] and the hidden scalar context [18][19][20][21][22][23]. Some works study both operators in tandem [24][25][26] or adopt an effective operator approach [27].…”

Section: Introductionmentioning

confidence: 99%

A tale of two portals: testing light, hidden new physics at future e + e − colliders

Liu

Wang

2017

J. High Energ. Phys.

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We investigate the prospects for producing new, light, hidden states at a future e + e − collider in a Higgsed dark U(1) D model, which we call the Double Dark Portal model. The simultaneous presence of both vector and scalar portal couplings immediately modifies the Standard Model Higgsstrahlung channel, e + e − → Zh, at leading order in each coupling. In addition, each portal leads to complementary signals which can be probed at direct and indirect detection dark matter experiments. After accounting for current constraints from LEP and LHC, we demonstrate that a future e + e − Higgs factory will have unique and leading sensitivity to the two portal couplings by studying a host of new production, decay, and radiative return processes. Besides the possibility of exotic Higgs decays, we highlight the importance of direct dark vector and dark scalar production at e + e − machines, whose invisible decays can be tagged from the recoil mass method.

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Detecting the Lμ−Lτ gauge boson at Belle II

Cited by 101 publications

References 106 publications

Predictions for the neutrino parameters in the minimal gauged $$\hbox {U}(1)_{L_\mu -L_\tau }$$ U ( 1 ) L μ - L τ model

Predictions for the neutrino parameters in the minimal gauged $$\hbox {U}(1)_{L_\mu -L_\tau }$$ U ( 1 ) L μ - L τ model

Lμ−Lτ gauge-boson production from lepton flavor violating τ decays at Belle II

A tale of two portals: testing light, hidden new physics at future e + e − colliders

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