[en] The mixing ratios (δ) and the internal conversion electron particle parameters (b₂) of the 121.8KeV transition in deformed ¹⁵²Sm nuclei were determined by comparing the γ-γ and γ-e angular correlation measurements made with the same source. The experimental apparatus was constructed with a surface barrier detector for electrons and two Ge(Li) detectors for gamma rays. The following results were obtained. 244.7 KeV - 121.8 KeV ; δ = -0.012±0.007 688.6 KeV - 121.8 KeV ; δ = 17.4±3.01 964.0 KeV - 121.8 KeV ; δ = 9.51±1.93 1112.0 KeV - 121.8 KeV ; δ = 12.30±2.05 1408.0 KeV - 121.8 KeV ; δ = 0.16±0.07 964.0 KeVγ - 121.8 keVe_k ; b₂ = 1.66±0.26 1408.0 KeVγ - 121.8 KeVe_k ; b₂ = 1.63±0.10 1408.0 KeVγ - 121.8 KeVe_L ; b₂ = 0.99±0.13 The results are compared with the theoretical values derived from the Pairing-Plus-Quadrupole model and from the Interacting-Boson-Approximation model, and an anomaly was found in the low-lying E2 transition for deformed ¹⁵²Sm nuclei. (Author)

[en] Neutrino oscillations in different schemes of neutrino mixing requiring an even number of charged leptons are investigated. The theory with only either Dirac or Majorana mass terms is considered. It is shown that the Dirac and Majorana mass cases are distinguishable through the character of their oscillations. In the first case there is one oscillation length and in the second case there are two oscillation lengths

No abstract available

[en] Exact expressions for the mixing parameters are obtained in terms of mass ratios in the standard Weinberg-Salam model with permutation symmetry S₃ for six quarks. The CP-violating phase is ignored, and there are no arbitrary parameters except for the quark masses. In the lowest order, the angles defined by Kobayashi-Maskawa are sin theta/sub 1/ = sin theta/sub c/ = (m/sub d//m/sub d/ + m/sub s/)/sup 1/2/, sin theta₃ = -sin theta/sub 3/ = -m²/sub s//m²/sub b/, and m/sub t/m/sub s/ greater than or equal to m/sub c/m/sub b/ = 7.2 GeV² or m/sub t/ greater than or equal to 24 GeV for m/sub s/ = 0.3 GeV

[en] The newly proposed finite symmetry Σ(81)is applied to the problem of neutrino tribimaximal mixing. The result is more satisfactory than those of previous models based on A₄ in that the use of auxiliary symmetries (or mechanisms) may be avoided. Deviations from the tribimaximal pattern are expected, but because of its basic structure, only tan²(Θ₁₂) may differ significantly from 0.5 (say 0.45) with sin²(2*Θ₂₃) remaining very close to unity, and Θ₁₃ very nearly zero. (authors)

[en] In the S₄ model, we work out the simplest possible scheme for neutrino masses. We find that ν/sub e/ and ν/sub μ/ have dominant massless components but not ν/sub tau/. The mixing matrix is completely determined and ν/sub e/-ν/sub tau/ and ν/sub μ/-ν/sub tau/ oscillations are possible with known mixing angles and only one deltam²

[en] We review the results of global analyses of short-baseline neutrino oscillation data in 3+1 and 3+2 neutrino mixing schemes

[en] Some problems connected with the high-precision study of neutrino oscillations are discussed. In the general case of n-neutrino mixing, a convenient expression for transition probability, in which only independent terms (and mass-squared differences) enter, is derived. For three-neutrino mixing, a problem of a definition of a large (atmospheric) neutrino mass-squared difference is discussed. The possibilities to reveal the character of neutrino mass spectrum in future reactor neutrino experiments are commented on as well.

[en] The leptonic mixing matrix is characterized by two large mixing angles, θ₁₂ ∼ 35 and θ₂₃ ∼ 45 and one small mixing angle θ₁₃. For several years, the data on neutrino oscillations were compatible with θ₂₃ ∼ 0, and were approximately described by the tribimaximal (TBM) mixing matrix. However, the recent results form Daya Baya and RENO reactor neutrino experiments have established that the smallest mixing angle θ₁₃ is rather large, i.e., θ₁₃ ∼ 9°. To account for the large reactor angle, we consider the lepton mixing matrix to be of the form U_PMNS = V_LU_TBM , where V_L is the unitary matrix needed to diagonalize the charged lepton mass matrix. The form of V_L is assumed to be of the form of CKM mixing matrix of the quark sector. We find that with this modification it is possible to accommodate the large observed reactor mixing angle θ₁₃. We also study the possibility of observing non-zero CP-violation in the leptonic sector with such extended tri-bimaximal mixing matrix. (author)

No abstract available