15,037 research outputs found
CP and T violation in neutrino oscillations
The conditions to induce appreciable CP-and T-odd effects in neutrino
oscillations are discussed. The propagation in matter leads to fake CP-and
CPT-odd asymmetries, besides a Bohm-Aharonov type modification of the
interference pattern. We study the separation of fake and genuine CP violation
by means of energy and distance dependence.Comment: To appear in the Proceedings of TAUP 99 Worksho
Twist transition of nematic hyperbolic hedgehogs
Stability of an idealized hyperbolic hedgehog in a nematic liquid crystal against a twist transition is investigated by extending the methodology of Rüdinger and Stark [Liq. Cryst. 26, 753 (1999)], where the hedgehog is confined between two concentric spheres. In the ideal hyperbolic-hedgehog the molecular orientation is assumed to rotate proportionally with respect to the inclination angle, θ (and in the opposite sense). However, when splay, k11, and bend, k33, moduli differ this proportionality is lost and the liquid crystal deforms relative to the ideal with bend and splay. Although slight, these deformations are shown to significantly shift the transition if k11/k33 is small. By increasing the degree of confinement the twist transition can be inhibited, a characteristic both hyperbolic and radial hedgehogs have in common. The twist transition of a hyperbolic defect that accompanies a particle is found to be well predicted by the earlier stability analysis of a thick shell
Low-Energy Predictions of Lopsided Family Charges
We consider the Froggatt-Nielsen (FN) mechanism reproducing the observed mass
hierarchies and mixing angles for quarks and leptons. The large - mixing suggested from recent Superkamiokande experiments on the
atmospheric neutrinos implies lopsided FN U(1) charges for the lepton doublets.
There are two possible charge assignments to generate the large - mixing. We point out that the two models with different charge
assignments have distinct low-energy predictions and hence they are
distinguishable in future neutrino experiments on such as CP violation and
decay.Comment: 14 pages,11 figures, Several discussions are sophisticate
Neutrino masses and mixing angles from leptoquark interactions
In this paper we show that the mixing between leptoquarks (LQ's) from
different multiplets can generate a non-trivial Majorana mass matrix
for neutrinos through one loop self energy diagrams. Such mixing can arise from
gauge invariant and renormalizable LQ-Higgs interaction terms after EW symmetry
breaking. We use the experimental indication on neutrino oscillation to find
constraints on specific combinations of LQ couplings to quark-lepton pairs and
to the SM higgs boson. These constraints are compared with the ones from
.Comment: The expressions for majorana mass matrix of neutrinos have been
corrected so that they are symmetric. Final version to be published in
Physical Review
Thermoelectricity of EuCu{2}(Ge{1-x}Si{x}){2} intermetallics
The evolution of the thermopower EuCu{2}(Ge{1-x}Si{x}){2} intermetallics,
which is induced by the Si-Ge substitution, is explained by the Kondo
scattering of conduction electrons on the Eu ions which fluctuate between the
magnetic 2+ and non-magnetic 3+ Hund's rule configurations. The Si-Ge
substitution is equivalent to chemical pressure which modifies the coupling and
the relative occupation of the {\it f} and conduction states.Comment: 2 pages, Proceedings of the SCES 2005 confernece. Physica B (2006),
in pres
Neutrinos and Gauge Unification
The approximate unification of gauge couplings is the best indirect evidence
for low-energy supersymmetry, although it is not perfect in its simplest
realizations. Given the experimental evidence for small non-zero neutrino
masses, it is plausible to extend the MSSM with three right-handed neutrino
chiral multiplets, with large Majorana masses below the unification scale, so
that a see-saw mechanism can be implemented. In this extended MSSM, the
unification prediction for the strong gauge coupling constant at M_Z can be
lowered by up to \sim 5%, bringing it closer to the experimental value at
1\sigma, therefore improving significantly the accuracy of gauge coupling
unification.Comment: 5 pages, LaTeX, 1 figur
Weak and Electromagnetic Nuclear Decay Signatures for Neutrino Reactions in SuperKamiokande
We suggest the study of events in the SuperKamiokande neutrino data due to
charged- and neutral-current neutrino reactions followed by weak and/or
electromagnetic decays of struck nuclei and fragments thereof. This study could
improve the prospects of obtaining evidence for production from oscillations and could augment the data sample used to disfavor
oscillations.Comment: 7 pages, latex, to appear in Phys. Rev. Let
Searching for Oscillations with Extragalactic Neutrinos
We propose a novel approach for studying oscillations
with extragalactic neutrinos. Active Galactic Nuclei and Gamma Ray Bursts are
believed to be sources of ultrahigh energy muon neutrinos. With distances of
100 Mpc or more, they provide an unusually long baseline for possible detection
of with mixing parameters down to
eV, many orders of magnitude below the current accelerator
experiments. By solving the coupled transport equations, we show that
high-energy 's, as they propagate through the earth, cascade down in
energy, producing the enhancement of the incoming flux in the low
energy region, in contrast to the high-energy 's, which get absorbed.
For an AGN quasar model we find the flux to be a factor of 2 to 2.5
larger than the incoming flux in the energy range between GeV and
GeV, while for a GRB fireball model, the enhancement is 10%-27% in the same
energy range and for zero nadir angle. This enhancement decreases with larger
nadir angle, thus providing a novel way to search for appearance by
measuring the angular dependence of the muons. To illustrate how the cascade
effect and the final flux depend on the steepness of the incoming
, we show the energy and angular distributions for several generic
cases of the incoming tau neutrino flux, for n=1,2 and
3.6. We show that for the incoming flux that is not too steep, the signal for
the appearance of high-energy is the enhanced production of lower
energy and their distinctive angular dependence, due to the contribution
from the decay into just below the detector.Comment: 11 pages, including 4 color figure
Filling-dependence of the zigzag Hubbard ladder for a quasi-one-dimensional superconductor Pr_2Ba_4Cu_7O_{15-delta}
We investigate filling dependence of the zigzag Hubbard ladder, using density
matrix renormalization group method. We illustrate the chemical-potential vs.
electron-density and spin gap vs. electron density curves, which reflect
characteristic properties of the electron state.On the basis of the obtained
phase diagram, we discuss the connection to a novel quasi-one-dimensional
superconductor PrBaCuO.Comment: 5 pages, 6 figures, fig.4 is adde
Neutrino Exotica in the Skew E_6 Left-Right Model
With the particle content of the 27 representation of E_6, a skew left-right
supersymmetric gauge model was proposed many years ago, with a variety of
interesting phenomenological implications. The neutrino sector of this model
offers a natural framework for obtaining small Majorana masses for nu_e, nu_mu,
and nu_tau, with the added bonus of accommodating 2 light sterile neutrinos.Comment: 12 pages, no figure, conclusion clarifie
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