15,907 research outputs found
Lepton mixing from the hidden sector
Experimental results indicate a possible relation between the lepton and
quark mixing matrices of the form U_PMNS \approx V_CKM^\dagger U_X, where U_X
is a matrix with special structure related to the mechanism of neutrino mass
generation. We propose a framework which can realize such a relation. The main
ingredients of the framework are the double seesaw mechanism, SO(10) Grand
Unification and a hidden sector of theory. The latter is composed of singlets
(fermions and bosons) of the GUT symmetry with masses between the GUT and
Planck scale. The interactions in this sector obey certain symmetries G_hidden.
We explore the conditions under which symmetries G_hidden can produce flavour
structures in the visible sector. Here the key elements are the basis-fixing
symmetry and mediators which communicate information about properties of the
hidden sector to the visible one. The interplay of SO(10) symmetry,
basis-fixing symmetry identified as Z2 x Z2 and G_hidden can lead to the
required form of U_X. A different kind of new physics is responsible for
generation of the CKM mixing. We present the simplest realizations of the
framework which differ by nature of the mediators and by symmetries of the
hidden sector.Comment: 30 pages, 6 figures; typo corrected, one reference added, version for
publication in Phys. Rev.
Atmospheric neutrinos: LMA oscillations, Ue3 induced interference and CP-violation
We consider oscillations of the low energy (sub-GeV sample) atmospheric
neutrinos in the three neutrino context. We present the semi-analytic study of
the neutrino evolution and calculate characteristics of the e-like events
(total number, energy spectra and zenith angle distributions) in the presence
of oscillations. At low energies there are three different contributions to the
number of events: the LMA contribution (from electron-neutrino oscillations
driven by the solar oscillation parameters), the Ue3-contribution proportional
to s13**2, and the Ue3 - induced interference of the two amplitudes driven by
the solar oscillation parameters. The interference term is sensitive to the
CP-violation phase. We describe in details properties of these contributions.
We find that the LMA, the interference and Ue3 contributions can reach 5 - 6%,
2 - 3% and 1 - 2 % correspondingly. An existence of the significant (> 3 - 5 %)
excess of the e-like events in the sub-GeV sample and the absence of the excess
in the multi-GeV range testifies for deviation of the 2-3 mixing from maximum.
We consider a possibility to measure the deviation as well as the CP- violation
phase in future atmospheric neutrino studies.Comment: 30 pages, RevTeX4.0, 11 figures; improved figure
Four-dimensional integration by parts with differential renormalization as a method of evaluation of Feynman diagrams
It is shown how strictly four-dimensional integration by parts combined with
differential renormalization and its infrared analogue can be applied for
calculation of Feynman diagrams.Comment: 6 pages, late
Structure of Matrix Elements in Quantum Toda Chain
We consider the quantum Toda chain using the method of separation of
variables. We show that the matrix elements of operators in the model are
written in terms of finite number of ``deformed Abelian integrals''. The
properties of these integrals are discussed. We explain that these properties
are necessary in order to provide the correct number of independent operators.
The comparison with the classical theory is done.Comment: LaTeX, 17 page
IBM: parameter symmetry, hidden symmetries and transformations of boson operators
A symmetry of the parameter space of interacting boson models IBM-1 and IBM-2
is studied. The symmetry is associated with linear canonical transformations of
boson operators, or, equivalently, with the existence of different realizations
of the symmetry algebras of the models. The relevance of the parameter symmetry
to physical observables is discussed.Comment: LATEX, 11 pages including 1 eps figure and 1 table prepared as an eps
figure; a talk given by A. M. Siirokov at XXII Symposium on Nuclear Physics,
Oaxtepec, Morelos, M\'exico, 5--8 January, 1999; to be published in Revista
Mex. Fi
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