8,784 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
Guide star catalogue data retrieval software 2
The Guide Star Catalog (GSC), being the largest astronomical catalog to date, is widely used by the astronomical community for all sorts of applications, such as statistical studies of certain sky regions, searches for counterparts to observational phenomena, and generation of finder charts. It's format (2 CD-ROM's) requires minimum hardware and is ideally suited for all sorts of conditions, especially observations. Unfortunately, the actual GSC data is not easily accessible. It takes the form of FITS tables, and the coordinates of the objects are given in one coordinate system (equinox 2000). The included reading software is rudimentary at best. Thus, even generation of a simple finder chart is not a trivial undertaking. To solve this problem, at least for PC users, GUIDARES was created. GUIDARES is a user-friendly program that lets you look directly at the data in the GSC, either as a graphical sky map or as a text table. GUIDARES can read a sampling of GSC data from a given sky region, store this sampling in a text file, and display a graphical map of the sampled region in projected celestial coordinates (perfect for finder charts). GUIDARES supports rectangular and circular regions defined by coordinates in the equatorial, ecliptic (any equinox) or galactic systems
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
Oscillations of very low energy atmospheric neutrinos
There are several new features in production, oscillations and detection of
the atmospheric neutrinos of low energies, E<100 MeV. The flavor ratio, r, of
muon to electron neutrino fluxes is substantially smaller than 2 and decreases
with energy, significant part of events is due to the decay of invisible muons
at rest, etc. Oscillations in two-layer medium (atmosphere - earth) should be
taken into account. We derive analytical and semi-analytical expressions for
the oscillation probabilities of these "sub-subGeV" neutrinos. The energy
spectra of the e-like events in water cherenkov detectors are computed and
dependence of the spectra on the 2-3 mixing angle, the 1-3 mixing and
CP-violation phase are studied. We find that variations of 2-3 mixing angle in
the presently allowed region change the number of e-like events by about 15 -
20 % as well as to distortion of the energy spectrum. The 1-3 mixing and
CP-violation can lead to ~10% effects. Detailed study of the sub-subGeV
neutrinos will be possible in future Megaton-scale detectors.Comment: 36 pages, 9 figure
Supersymmetric pairing of kinks for polynomial nonlinearities
We show how one can obtain kink solutions of ordinary differential equations
with polynomial nonlinearities by an efficient factorization procedure directly
related to the factorization of their nonlinear polynomial part. We focus on
reaction-diffusion equations in the travelling frame and
damped-anharmonic-oscillator equations. We also report an interesting pairing
of the kink solutions, a result obtained by reversing the factorization
brackets in the supersymmetric quantum mechanical style. In this way, one gets
ordinary differential equations with a different polynomial nonlinearity
possessing kink solutions of different width but propagating at the same
velocity as the kinks of the original equation. This pairing of kinks could
have many applications. We illustrate the mathematical procedure with several
important cases, among which the generalized Fisher equation, the
FitzHugh-Nagumo equation, and the polymerization fronts of microtubulesComment: 13 pages, 2 figures, revised during the 2nd week of Dec. 200
Dynamics of diproton formation in the and reactions in the GeV region
Mechanisms for the production of diproton pairs, , in the
reaction are studied at proton beam energies 0.5 -- 2 GeV in
kinematics similar to those of backward elastic scattering. This reaction
provides valuable information on the short-range and interactions
that is complementary to that investigated in the well known and
processes. The reaction is related to the
subprocesses and using two different
one--pion--exchange (OPE) diagrams. Within both these models a reasonable
agreement could be obtained with the data below 1GeV. The similar energy
dependence of the and cross sections and the small
ratio of about 1.5% in the production of to deuteron final states
follow naturally within the OPE models.Comment: 10 pages, 7 figures, Late
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