共查询到20条相似文献,搜索用时 15 毫秒
1.
Jai Kumar Singhal 《Pramana》2004,62(5):1029-1040
We examine the effects of mixing induced light heavy charged lepton neutral currents on the partial wave amplitude for the
process l+l− →ZZ (withl = e,μ or τ). By imposing the constraints that the amplitude should not exceed the perturbative unitarity limit at high energy (√s
= Λ), we obtain bounds on light heavy charged lepton mixing parameter sin2(2θ
L
a
) where θ
L
a
is the mixing angle of the ordinary charged lepton with its exotic partner. For Λ = 1 TeV, no bound is obtained on sin2 (2θ
L
a
) form
E < 0.69 TeV. However, sin2 (2θ
L
a
) ≤ 1.52×10−5 form
E = 5 TeV, sin2 (2θ
L
a
) ≤ 2.41 ×10−7 form
E = 10 TeV. Similarity for Λ = ∞ no bound is obtained on sin2 (2θ
L
a
) for mE < 1.97 TeV and sin2 (2θ
L
a
) ≤ 0.15 form
E = 5 TeV and sin2 (2θ
L
a
) ≤ 3.88×10-2 form
E = 10 TeV. 相似文献
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Yukio Tomozawa 《Physics letters. [Part B]》1981,104(2):136-140
A generalized mixing matrix for leptons is presented based on a composite model of quarks and leptons. The mixing matrix is expressed in terms of one parameter, which is determined either by discussing that it is identical to that of the quark mixing matrix or by assuming that the observed solar neutrino flux results from neutrino oscillations. 相似文献
5.
Y. Koide 《Zeitschrift fur Physik C Particles and Fields》1989,45(1):39-41
By starting from a mass matrix with family-independent mixing (the so-called “democratic” family mixing) and by requiring some simple constraints on the additional mass terms, but without any small parameters, a mass relation which is in excellent agreement with experiment is derived for charged leptons. 相似文献
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Recent neutrino experiments suggest strong evidence of tiny neutrino masses and the lepton-flavor mixing. Neutrino-oscillation
solutions for the atmospheric neutrino anomaly and the solar neutrino deficit can determine the texture of the neutrino mass
matrix according to the neutrino mass hierarchies as Type A: , Type B: , and Type C: , where is the i-th generation neutrino mass. In this paper we study the stability of the lepton-flavor mixing matrix against quantum corrections
for all three types of mass hierarchy in the minimal supersymmetric Standard Model with an effective dimension-five operator
which gives the Majorana masses of neutrinos. The relative sign assignments of neutrino masses in each type play crucial role
for the stability against quantum corrections. We find that the lepton-flavor mixing matrix of Type A is stable against quantum
corrections, and that of Type B with the same (opposite) signs of and are unstable (stable). For Type C, the lepton-flavor-mixing matrix approaches the definite unitary matrix according to the
relative sign assignments of the neutrino mass eigenvalues as the effects of quantum corrections become large enough to neglect
the squared mass differences of neutrinos.
Received: 24 June 1999 / Revised version: 23 December 1999 / Published online: 17 March 2000 相似文献
9.
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 相似文献
10.
Smirnov AY 《Physical review D: Particles and fields》1993,48(7):3264-3270
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《Nuclear Physics B》1995,437(3):491-519
Analytic expressions of lepton-flavour- and lepton-number-violating decays of charged leptons are derived in the context of general SU(2)L ⊗ U(1)Y seesaw scenarios that are motivated by grand unified theories (GUT's) or superstring models, in which left-handed and/or right-handed neutral singlets are present. Possible constraints imposed by cosmology and low-energy data are briefly discussed. The violation of the decoupling theorem in flavour-dependent graphs due to the presence of heavy neutral leptons of Dirac or Majorana nature is emphasized. Numerical estimates reveal that the decays τ− → e− e− e+or τ− → e− μ− μ+ can be as large as ∼ 10−6, which may be observed in LEP experiments or other τ factories. 相似文献
13.
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. 相似文献
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N. Haba Y. Matsui N. Okamura M. Sugiura 《The European Physical Journal C - Particles and Fields》1999,10(4):677-680
We study an energy-scale dependence of the lepton flavor-mixing matrix in the minimal supersymmetric standard model with
the effective dimension-five operators, which give Majorana masses of neutrinos. We analyze the renormalization group equations
of the coefficients () of these effective operators under an approximation that neglects terms of order . We find that only (where is the generation number) real independent parameters in the lepton flavor-mixing matrix depend on the energy scale. In particular,
all the phases in are scale-independent.
Received: 10 April 1999 / Revised version: 23 May 1999 / Published online: 28 September 1999 相似文献
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18.
Dr. P. Kroll 《Zeitschrift für Physik A Hadrons and Nuclei》1972,252(3):219-236
A Regge-pole model with π-, ?-,A 2- andR-meson exchange and absorptive corrections are used to reproduce the π± photoproduction data in the larges, small ¦t¦ region. The starting point for the calculation of the absorptive corrections is the Regge-pole model for invariant functions. 相似文献
19.
We examine relativistic effects in a coupled channel mixing calculation of corrections to charmonium energy levels. We find that the relativistic effect on the coupled channel mixing is large. Thus a relativistic treatment is necessary and may possibly lead to a larger admixture ofD andS states. 相似文献
20.
The electromagnetic radiative corrections toe + e ? -annihilation into lepton pairs are calculated including hard photon bremsstrahlung in the standard and extended electroweak models. For \(\sqrt s \) = 38 GeV we find for the standard model, that the radiative corrections toZ-exchange reduce the charge asymmetry up to 1% which is mainly caused by the virtual and soft photon parts of the corrections. For models with a higher forward-backward asymmetry the situation is found to be quite similar. 相似文献