Lepton number violation in softly broken supersymmetry (II)

We study the implications of explicit lepton-number violating soft operators in a general low-energy effective theory with softly broken supersymmetry. Nonzero but relatively small VEVs of scalar neutrinos could exist. In the case where the VEVs of scalar neutrinos vanish, appreciable coefficients of the lepton-number violating soft operators are allowed. We also emphasize the role played by the mixing between the superpartners of the left- and right-handed leptons in the lepton family number violating process μ→eγ.     

Lepton number violation at the LHC with leptoquark and diquark

We investigate a model in which tiny neutrino masses are generated at the two-loop level by using scalar leptoquark and diquark multiplets. The diquark can be singly produced at the LHC, and it can decay into a pair of leptoquarks through the lepton number violating interaction. Subsequent decays of the two leptoquarks can provide a clear signature of the lepton number violation, namely two QCD jets and a pair of same-signed charged leptons without missing energy. We show that the signal process is not suppressed while neutrino masses are appropriately suppressed.     

Lepton and flavor violation in SUSY models

Lepton and flavor violating processes resulting from neutral scalar-lepton mixing are examined in the context of supersymmetric models. Contributions arising at the one-loop level for μ → eγ, μ → 3e, μμ ⇄ ee as well as for neutrinoless ββ-decay are found to be suppressed for a general class of supersymmetry breaking parameters.     

Lepton flavor violation and seesaw symmetries

When the standard model is extended with right-handed neutrinos the symmetries of the resulting Lagrangian are enlarged with a new global U(1) _R Abelian factor. In the context of minimal seesaw models we analyze the implications of a slightly broken U(1) _R symmetry on charged lepton flavor violating decays. We find, depending on the R-charge assignments, models where charged lepton flavor violating rates can be within measurable ranges. In particular, we show that in the resulting models due to the structure of the light neutrino mass matrix muon flavor violating decays are entirely determined by neutrino data (up to a normalization factor) and can be sizable in a wide right-handed neutrino mass range.     

Lepton decay constants of light mesons

A theory of lepton decay constants based on the path-integral formalism is given for chiral and vector mesons. Decay constants of the pseudoscalar and vector mesons are calculated and compared to other existing results.     

Lepton number nonconservation in supersymmetric theories

We consider a class of supersymmetric models lepton number nonconservation due to mixing of scalar leptons. It is shown that a range of parameters exists such that the processes μ→eγ, μ→eγγ, μ→3e, μ⁺ e ^?→μ^? e ⁺ are strongly suppressed, whereas the decay \(\mu \to e\tilde \gamma \tilde \gamma \) can proceed with a rate \(BR(\mu \to e\tilde \gamma \tilde \gamma ) \lesssim 0.01\) . The signatures of such decay can be the production of right-handed electrons with the energy aroundm _μ/3 and modification of the energy spectrum of the electrons in that region as compared with the standard model prediction.     

Parity violation in high energy Lepton pair production and QCD

We use the quark-parton model with perturbative QCD corrections in the Weinberg-Salam theory to calculate a parity-violating asymmetry in inclusive lepton pair production. We estimate the asymmetry proportional to the triple correlation $\text{〈}\text{P·l}{}^{\mathrm{+}}\text{×}\text{l}{}^{\mathrm{?}}\text{〉}$ of the lepton momenta $\text{l}{}^{\mathrm{+}}\text{and}\text{l}{}^{\mathrm{?}}$ and the incident hadron momentum $\text{P}$. We find that a nonzero asymmetry requires inclusion of nonperturbative effects.     

T violation in neutralino decay

We show that in the supersymmetric standard electroweak theory the neutralino decay causesCP violating phenomena. It will be possible to observeT odd asymmetry in the angular distribution if the trilepton decay of theW boson is found. We also discuss the constraint on the magnitude ofCP violation by the electric dipole moment of the neutron.     

Lepton flavour violation in the constrained MSSM with constrained sequential dominance

We consider charged lepton flavour violation (LFV) in the constrained minimal supersymmetric Standard Model, extended to include the see-saw mechanism with constrained sequential dominance (CSD), where CSD provides a natural see-saw explanation of tri-bimaximal neutrino mixing. When charged lepton corrections to tri-bimaximal neutrino mixing are included, we discover characteristic correlations among the LFV branching ratios, depending on the mass ordering of the right-handed neutrinos, with a pronounced dependence on the leptonic mixing angle θ₁₃${\theta }_{13}$ (and in some cases also on the Dirac CP phase δ).     

Lepton flavor violation in lopsided models and a neutrino mass model

A widely adopted theoretical scheme to account for the neutrino oscillation phenomena is the see-saw mechanism together with the “lopsided” mass matrices, which is generally realized in the framework of supersymmetric grand unification. We will show that this scheme leads to large lepton flavor violation at low energy if supersymmetry is broken at the GUT or Planck scale. Especially, the branching ratio of already exceeds the present experimental limit. We then propose a phenomenological model which can account for the LMA solution to the solar neutrino problem and at the same time predict a branching ratio of below the present limit. Received: 18 November 2002 / Published online: 14 February 2003     

Lepton flavor violation and non-unitary lepton mixing in low-scale type-I seesaw

Journal of High Energy Physics - It is sometimes believed that small quantum gravity effects can encode information as ‘delicate correlations’ in Hawking radiation, thus saving...     

Neutrinoless double beta decay and a new limit on the lepton number violation

We have calculated the neutrinoless double beta decay rate of ⁷⁶Ge. We take into account for the first time a relativistic correction to the nuclear current including weak magnetism. Its effect is to cancel a considerable part of the decay amplitude and we obtain less stringent upper limits on the neutrino Majorana mass and the right-handed weak leptonic current compared with previous calculations.     

Lepton mass correction in partial wave analyses of charmed meson semi-leptonic decays

We derive a parameterization formula for the partial wave analyses of charmed meson semi-leptonic decays while considering the effects of lepton mass. Because the proposed super-tau-charm factory will reach a significantly enhanced luminosity and BESIII is collecting new ψ(3770) → ■ data, our results will help improve the measurement precision of future partial wave analyses of charmed meson semi-muonic decays.     

Spontaneous CP violation and neutral B meson decays

A model in which CP is spontaneously broken is described; it solves the strong CP problem and provides an additional mechanism for weak CP violation. This is the aspon model. Application to B decays leads to predictions for CP asymmetries much smaller than expected from the KM mechanism of explicit CP breaking.