TeV-scale bileptons, see-saw type II and lepton flavor violation in core-collapse supernova

Electrons and electron neutrinos in the inner core of the core-collapse supernova are highly degenerate and therefore numerous during a few seconds of explosion. In contrast, leptons of other flavors are non-degenerate and therefore relatively scarce. This is due to lepton flavor conservation. If this conservation law is broken by some non-standard interactions, ν _e are converted to ν _μ , ν _τ , and e are converted to μ. This affects the supernova dynamics and the supernova neutrino signal. We consider lepton flavor violating interactions mediated by scalar bileptons, i.e. heavy scalars with lepton number 2. It is shown that in case of TeV-mass bileptons the electron Fermi gas is equilibrated with non-electron species inside the inner supernova core at a time scale ～(1–100) ms. In particular, a scalar triplet which generates neutrino masses through the see-saw type II mechanism is considered. It is found that the supernova core is sensitive to yet unprobed values of masses and couplings of the triplet.     

A supersymmetric extension of the Weinberg-Salam model

By use of Slavnov's procedure, a supersymmetric extension of the Weinberg-Salam model of lepton interactions is obtained. At low energies (E ? m_W), that model is approached very closely. In addition, we get four heavy leptons (m?m_W) and a number of heavy scalars, plus a normally unobservable new neutrino.     

Fermion masses and mixing angles in anSU(2) L ×U(1) model with horizontal interactions

AnSU(2) _L ×U(1) horizontal model is presented, in which fermions mass splitting, quark and lepton family mixing is attributed to the presence of the horizontal interactions. In the quark sector, the Cabibbo angle and the Cabibbo-like angles are evaluated. In the lepton sector, the neutrinos mixing angles, which orginate from the charged leptons mixing, are calculated, the scale of the horizontal interactions is related to the neutrino oscillation length.     

Heavy leptons,lepton mixing,and nonconservation of lepton-type number

Introducing a new weak doublet of heavy leptons, one is led to a mixing of the various lepton states with respect to the weak interaction and subsequently to the violation of electron and muon number conservation (e.g., the decay μ→eγ). The new charged lepton can only decay via such a mixing and is therefore relatively long-lived (τ>10^?11 sec). It can be produced singly in ν_μ nucleus scattering at high energies. Various other phenomenological consequences are discussed.     

Photoproduction of large transverse momentum mesons and production of large-pT photons and leptons in proton-proton collisions

The photoproduction of large transverse momentum mesons is examined in a leading particle model using the techniques of the covariant parton model. In the leading particle model the large-p_T meson is produced in a high-energy, wide-angle scattering: γ + q → M + q. Numerical results such as inclusive cross sectioons, angular distributions and particle ratios are presented for the pseudoscalar mesons. The Landshoff-Polking-horne quark-fusion model is then applied to the production of large transverse momentum photons and leptons in proton-proton collisions. In the lepton case this model differs from the usual Drell-Yan mechanism in that the lepton pair has a small invariant mass but comes from a large-p_T virtual photon.     

Trimuons in SU(3) gauge models

We discuss models of weak interactions which can account for the recently observed μ^?μ^?μ⁺ events in v_μ reactions by allowing for the production of a new heavy neutral lepton and a new quark. One model is based on an SU(3) × U(1) gauge theory in shich the left-handed leptons are classified in anti-triplets. The second model catagorizes the leptons in an octet in accord with the more restrictive SU(3) weak gauge theory.     

Lepto-quark matter

In certain extensions of the standard model with additionalU(1) gauge symmetries, the anomalies between the quarks and leptons no longer cancel. It is shown that the anomalies can be cancelled by invoking representations oflepto-quark fermions. Lepto-quarks represent new fermionic matter that carries quark as well as lepton numbers. An extension of the standard model with three and four families of conventional quarks and leptons is presented in which freedom from anomalies is secured through the presence of lepto-quark matter representations. The gauge symmetry of the model isSU(2) _L XU(1) _q XU(1) _l whereU(1) _q andU(1) _l refer to distinct hypercharge sources for the quarks and the leptons.     

NEUTRINO MAGNETIC MOMENT IN SUPERSTRING INSPIRED MODELS

In superstring E₆ models right-handed leptonic currents can arise from the mixing between the ordinary leptons and tha exotic leptons. Contributions to the neutrino magnetic moment due to this new interaction are examined. Although the result appears to be directly proportional to the heavy exotic charged lepton mass, it is shown, however, that the mixing is proportional to the ratio of the neutrino mass and the exotic lepton mass. The combination of these two factors yields a result which is of the order of that given by the SU(2)_LxU(1)_Y model.     

A determination of sin2θ w and the lepton and quark electroweak couplings frome + e − data

Published data on lepton pair and quark pair final states ine ⁺ e ^? annihilation have been analysed in a self consistent way to yield values for the lepton and quark weak vector and axial vector couplings. Generation universality has been tested for the leptons and under the assumption of the standard model of the weak interaction, the parameter sin²θ _w has been determined separately for the lepton and quark sector. In the renormalisation scheme α,G _μ and sin²θ _w , the result for the lepton final states is sin²θ _w = 0.212±0.014 and for the hadron final states, sin²θ _w = 0.236±0.015. The combined result for this single parameter in the model is sin²θ _w = 0.223±0.011±0.007, corresponding tom _Z =93.0 _?1.8 ^+2.0 GeV.     

Production of prompt leptons in a cluster model

Prompt lepton production in hadron collisions is explained in a cluster production model, by assuming that the clusters have a small branching ratio for decay into leptons. The production of low mass and small momentum clusters, normalized to reproduce pionization, can explain the observed large increases of e/π ratio for decreasing p_bdT at large angles and the decreasing values of ω/π with increasing x_lab near the forward direction. The present model predicts a large increase of the e/ω ratio near the forward direction as x_lab increases.     

Hierarchy of interactions and mass relations in asymptotically free E6 model of unified interactions

The hierarchy of gauge interactions within the E₆ model is proved, and the vector and spinor field masses are obtained. The mass spectrum of the charged W-bosons is found, and the mass scale is fixed so that the mass of the lightest of them is about 70 GeV. The lepton spectroscopy is studied and a new charged lepton, with mass of order 4–8 GeV is predicted. For the low-energy phenomenology, the model may be considered as a theory of 6 flavoured quarks and 4 charged leptons, each with its neutrino. Being 4-component the neutrinos are massive except for the ν_e (m_νe = 0, exactly) and ν_μ (m_νμ ≈ 0, approximately) particles. The problem of the “superfluous” particles which as a rule accompanies the asymptotic freedom in such theories is also briefly discussed.     

具有整体代对称性的左右对称模型中的中微子质量

本文基于具有整体U(1)代对称性的SU(2)_L×SU(2)_R×U(1)模型推导了轻子的味混合矩阵,对中微子的质量问题进行了研究.在本文的模型中,产生轻子Dirac质量的汤川耦合拉格朗日密度具有整体U(1)代对称性,所以,模型中的带电轻子质量矩阵和中微子Dirac质量矩阵是Fritzsch形式的.但是,中微子除了具有Dirac质量,一般还具有Majorana质量,在这种一般情况下, 关键词： 中微子质量 轻子味混合矩阵 左右对称模型 代对称性     

Is there a new neutral lepton?

We discuss conservation laws of lepton flavors within the context of unified weak and electromagnetic gauge theories. We show that the present upper limit on the new (U) lepton-number violating processes U→3 charged leptons already requires the presence of a neutral lepton in the SU(2) ? U(1) theory. We discuss some of the possibilities and point out the constraints implied by lowering the bounds on μ→eγ and U→3 charged leptons.     

Must the new heavy lepton have it's own neutrino?

We consider a minimal gauge theory of leptons, including only e, μ, the newly found charged lepton L and two massless two-component neutrinos.The model implies muon number non conservation. The present limit on μ+Nucleus→e+Nucleus leads to a branching ratio for μ→eγ not larger than 1.7 × 10^?12. Striking violations of μ?e universality in L decays are predicted.     

Phenomenology of the standard model under conditions of spontaneously broken mirror symmetry

Spontaneously broken mirror symmetry is able to reproduce observed qualitative properties of weak mixing for quark and leptons. Under conditions of broken mirror symmetry, the phenomenology of leptons—that is, small neutrino masses and a mixing character other than that in the case of quarks—requires the Dirac character of the neutrinos and the existence of processes violating the total lepton number. Such processes involve heavy mirror neutrinos; that is, they proceed at very high energies. Here, CP violation implies that a P-even mirror-symmetric Lagrangian must simultaneously be T-odd and, according to the CPT theorem, C-odd. All these properties create preconditions for the occurrence of leptogenesis, which is a mechanism of the emergence of the baryon–lepton asymmetry of the universe in models featuring broken mirror symmetry.     

About the leptons pairs production in hardonic collisions

Using the generalized vector dominance model a connection is established between the e⁺e^? annihilation and the lepton pair production which can explain the important number of leptons observed at large transverse momenta.     

Charge asymmetry ratio as a probe of quark flavour couplings of resonant particles at the LHC

We show how a precise knowledge of parton distribution functions, in particular those of the u and d quarks, can be used to constrain a certain class of New Physics models in which new heavy charged resonances couple to quarks and leptons. We illustrate the method by considering a left–right symmetric model with a W′ from a SU(2) _R gauge sector produced in quark–antiquark annihilation and decaying into a charged lepton and a heavy Majorana neutrino. We discuss a number of quark and lepton mixing scenarios, and simulate both signals and backgrounds in order to determine the size of the expected charge asymmetry. We show that various quark–W′ mixing scenarios can indeed be constrained by charge asymmetry measurements at the LHC, particularly at \(\sqrt{s}= 14\) TeV.     

Lepton mixing, μ → e + γ decay and neutrino oscillations

The μ → eγ decay is investigated in a gauge theory with lepton mixing under the assumption that in nature there exist heavy leptons. It is shown that for lepton masses of the order of a few GeV the μ → eγ decay probability may well be close to its experimentally determined upper limit. The relation between such a decay process and neutrino oscillations is briefly considered.     

Selection rules in a unified gauge model of leptons and hadrons

Decay modes and lifetimes of quarks, vector mesons and protons are determined for the unified model of leptons and hadrons recently proposed by Pati and Salam. It is found that while both the quarks and gauge mesons decay too rapidly to be observed, protons will be comfortably stable against decay into leptons, consistent with earlier estimates and existing experimental evidence. It is of special interest that while quarks may not be directly observable, their presence may be verified owing to the uniqueness of their preferred decay into quite a large number of pions. We also discuss an anomalous lepton-hadron scattering process whose occurrence would imply the presence of exotic SU(4) gluons carrying both baryon and lepton number.     

Neutrino magnetic moment inN=1 minimal supergravity

The complete one-loop supersymmetric (SUSY) correction to the magnetic moment (NMM) of a Dirac neutrino is calculated with allowance for mixing between the scalar leptons and for mixing between theW-gaugino and Higgs fermions. The contribution from the charged Higgs loop is negligible for all practical purpose. We thoroughly study the dependence of NMM on the SUSY parameters. The SUSY contribution to the NMM can be a few times less than or comparable to the value of the standard model (with a right-handed neutrino singlet added). The SUSY correction to the NMM increases with decreasing β value (tan β=〈H ₂〉/〈H ₁〉), and is not very sensitive to the charged scalar lepton mass.