Empirical lepton-quark mass formula: Four dimensional state space for fermion structure?

It is observed that a simple mass formula of the formm =¯mQ ²(exp) is wholly consistent with experimental measurements and quark model estimates for all 12 fundamental fermions. Here¯m = 433.3 MeV is an input (mean fermion mass) constant,Q is the charge number of the lepton or quark, and is a real root of a quartic equation that brings in a principal quantum numbern (= 0, 1, 2, 3). The charged lepton masses are given accurately to within 0.3 of 1%, all neutrino masses are zero, and the top mass is predicted by the formula to be close tom _t = 163.6 GeV.     

τ lepton decays

We discuss recent results on τ lepton physics obtained at the BABAR, Belle and KEDR detectors They include tests of lepton universality using new measurements of T lepton mass and some branching fractions Also described are selected results on τ lepton hadronic decays coming from BABAR and Belle.     

τ lepton decays

We discuss recent results on τ lepton physics obtained at the BABAR,Belle and KEDR detectors.They include tests of lepton universality using new measurements of τ lepton mass and some branching fractious.Also described are selected results on τ lepton hadronic decays coming from BABAR and Belle.     

Neutrino masses from SUSY: Different contributions and their implications

We discuss the various sources of neutrino masses in supersymmetric standard models with explicit lepton number violation. We show that the bilinear lepton number violating soft terms in models with either bilinear or trilinear lepton number violating couplings in the superpotential, play an important role in determining the neutrino mass spectrum. A comparative study of the neutrino mass spectrum and its implications for the present neutrino anomalies in these models is presented.     

A TROUBLE FOR COMPOSITE QUARK AND LEPTON MODELS

In composite quark and lepton models a factor which depends on the quark or lepton mass ratio appears in the effective weak coupling constant of quarks and leptons. It comes from the Lorentz (contraction of the composite quark and lepton wave functions and may cause a trouble for their weak coupling constant universality.     

Decay of PSI and upsilon into a lepton pair and gluons

We calculate the decay of a heavy vector quarkonium state into a lepton pair and two gluon jets, in lowest order QCD. We present branching ratios, and the lepton pair spectrum as a function of its invariant mass, and of the missing mass recoiling against it.     

Mass extrapolation of quarks and leptons to higher generations

An empirical mass formula is tested for the basic fermion sequences of charged quarks and leptons. This relation is a generalization of Barut’s mass formula for the lepton sequence (e, μ, τ......). It is found that successful mass extrapolation to the third and possibly to other higher generations (N>2) can be obtained with the first and second generation masses as inputs, which predicts the top quark massm _t to be around 20 GeV. This also leads to the mass ratios between members of two different sequences (i) and (i′) corresponding to the same higher generations (N>2).     

See-saw neutrino masses induced by a triplet of leptons

Neutrinos can acquire mass through the see-saw mechanism by extending the lepton sector of the Standard Model. The most generalSU(2) _L assignments allowed for the exotic leptons are the singlet and triplet representations. A model is constructed involving a triplet of exotic leptons. In this model lepton number is broken. Therefore lepton number violating processes, in particular those involving the lepton triplet, could provide distinctive experimental signatures.     

Radiative corrections to semileptonic decays of charged hyperons

We have studied the radiative corrections to the lepton energy spectrum in semileptonic hyperon decays. The calculation is performed relativistically for the baryons as well as for the leptons, under the assumption of the effective current-current interaction of the V-?A type for the baryonic part. We obtain the explicit formula of radiative corrections to the lepton energy spectrum which we can exactly evaluate in case of charged hyperon decays. Numerical values of the radiative corrections to the decays rate and the shape of the lepton energy spectrum are also given for some decay modes. It is shown that the spectral shape is little affected by the radiative corrections.     

Depletion of atmospheric muon-neutrino fluxes and structure of Majorana mass matrix

We study the structures of the Dirac and Majorana mass matrices which give rise to the large lepton mixing expected from the depleted atmospheric muon-neutrino flux. In the case that the Majorana mass matrix has a hierarchy for generations, a certain kind of the neutrino Dirac mass matrix with the hierarchical structure leads to the large lepton mixing between the second generation and the third one. Our model-independent analyses serve the model-building of the mass matrices based on the quark-lepton unified theory.     

Radiative transmission of lepton flavor hierarchies

We discuss a one loop model for neutrino masses which leads to a seesaw-like formula with the difference that the charged lepton masses replace the unknown Dirac mass matrix present in the usual seesaw case. This is a considerable reduction of parameters in the neutrino sector and predicts a strong hierarchical pattern in the right handed neutrino mass matrix that is easily derived from a U(1)_H family symmetry. The model is based on the left–right gauge group with an additional Z₄ discrete symmetry which gives vanishing neutrino Dirac masses and finite Majorana masses arising at the one loop level. Furthermore, it is one of the few models that naturally allow for large (but not necessarily maximal) mixing angles in the lepton sector. A generalization of the model to the quark sector requires three iso-spin singlet vector-like down type quarks, as in E₆. The model predicts an inert doublet type scalar dark matter.     

A study of B meson oscillations using hadronic Z0 decays containing leptons

An event sample enriched in semileptonic decays of b hadrons is selected using an inclusive lepton selection from approximately 3.0 million hadronic Z⁰ decays collected with the OPAL detector. This sample is used to investigate B meson oscillations by reconstructing a proper decay time for the parent of each lepton, using a jet charge method to estimate the production flavour of this parent, and using the lepton charge to tag the decay flavour. We measure the mass difference between the two B⁰ _d mass eigenstates     

论反常作用、轻子结构和μ-e质量差

本文提出了反常作用的μ荷观点,μ荷不仅是一种反映μ-e禁戒性的量子数,而且是反常作用的承担者。在此观点下,讨论了轻子结构和μ-e质量差,得到了关于轻子结构的一些普遍定理。例如,证明了电子的反常作用和电磁作用形状因子相同等。在讨论轻子结构的基础上,得到了将μ-e质量差和轻子的电磁结构相联系的公式,证明了主要由于电磁作用干涉产生的μ荷-μ矩作用是反常作用自能的主要部分,它是负值,故是电子参与反常作用。利用电子的电磁结构数据能合理地解释μ-e质量差,而后者也提供了有关电子电磁结构的进一步知识。     

Low mass lepton pair production and pion dynamics in ultrarelativistic heavy ion collisions

The production of lepton pairs with low invariant mass as probes for the pion dynamics in relativistic nuclear collisions is discussed in some detail. We emphasize the implications of a possible large positive pion chemical potential for the production rate of lepton pairs. We find a strong enhancement in the low invariant mass region, \(2m_\pi \leqslant M_{\mu ^ + \mu ^ - } \leqslant 600\,MeV\) , for lepton pairs which are produced via the annihilation of pions in the hot and dense collision zone. Various sources of background which could mask this enhancement are discussed in some detail. We present and compare calculations for dilepton mass spectra based on different nuclear collision scenarios. It is found that the di-muon mass spectrum can serve as a useful probe to distinguish between these different scenarios.     

Search for lepton flavor violating decays tau(+/-) --> l(+/-)pi0, l(+/-)eta, l(+/-)eta'

A search for lepton flavor violating decays of the tau lepton to a lighter mass lepton and a pseudoscalar meson has been performed using 339 fb;{-1} of e;{+}e;{-} annihilation data collected at a center-of-mass energy near 10.58 GeV by the BABAR detector at the SLAC PEP-II storage ring. No evidence of a signal has been found, and upper limits on the branching fractions are set at the 10;{-7} level.     

An analytical expression of the asymptotic QED cross-section of four lepton two pair production in γγ collisions

For the first time we have obtained an analytical QED asymptotic formula for the γγ production of two lepton pair with equal or unequal masses.     

SU(3) LEPTON MODEL AND THE DYNAMICAL GENERATION OF LEPTON MASS DIFFERENCES

A SU (3) lepton model is discussed in which the left- and right-handed leptons are on equal footing and sin²θ_w=1/4 is obtained. Dynamical symmetry breaking is investigated to see if lepton mass difference can be generated in this way so as to reduce the number of Higgs scalars and Yukawa coupling constants. Calculating the effective potential up to two-loop graphs gives the results that composite Goldstone bosons can exist only when the remained Yukawa coupling constant lies within a certain range. The corresponding heavy lepton mass obtained is about 130 GeV.     

Baryogenesis from mixing of lepton doublets

It is shown that the mixing of lepton doublets of the Standard Model can yield sizable contributions to the lepton asymmetry, that is generated through the decays of right-handed neutrinos at finite temperature in the early Universe. When calculating the flavour-mixing correlations, we account for the effects of Yukawa as well as of gauge interactions. We compare the freeze-out asymmetry from lepton-doublet mixing to the standard contributions from the mixing and direct decays of right-handed neutrinos. The asymmetry from lepton mixing is considerably large when the mass ratio between the right-handed neutrinos is of order of a few, while it becomes Maxwell-suppressed for larger hierarchies. For an intermediate range between the case of degenerate right-handed neutrinos (resonant leptogenesis) and the hierarchical case, lepton mixing can yield the main contribution to the lepton asymmetry.     

LMA solution to the solar neutrino problem and a phenomenological charged lepton mass matrix

We propose a phenomenological form of the charged lepton mass matrix which extends the idea of a ”lopsided” mass matrix found in the literature. The features of the form are that both the 2-3 and 1-3 elements of the charged lepton mass matrix are of order 1 and that the small elements have a new structure. This form leads to the interesting result that both large atmospheric and solar neutrino mixing can be accounted for by the matrix. Another interesting result of this mass matrix is that it leads to very small 1-3 mixing in the lepton sector and can suppress the branching ratio of under the present experimental limit in the supersymmetric see-saw case. Received: 3 October 2002 / Revised version: 10 November 2002 / Published online: 24 January 2003 RID="a" ID="a" e-mail: bixj@mail.tsinghua.edu.cn RID="b" ID="b" e-mail: dyb@itp.ac.cn     

A possible interpretation of CDF dijet mass anomaly and its realization in supersymmetry

Recently, the CDF Collaboration reports an anomaly in dijet mass distribution in association with a lepton and missing energy. We discuss a possibility that the origin of the lepton and missing energy comes not from a W boson but a new boson particle, which is also responsible for the dijet mass peak. We show that such a situation can be realized in the framework of the minimal supersymmetric standard model and the dijet anomaly can be explained.