1,409 research outputs found
Constructing Dirac linear fermions in terms of non-linear Heisenberg spinors
We show that the massive (or massless) neutrinos can be described as special
states of Heisenberg nonlinear spinors. As a by-product of this decomposition a
particularly attractive consequence appears: the possibility of relating the
existence of only three species of mass-less neutrinos to such internal
non-linear structure. At the same time it allows the possibility that neutrino
oscillation can occurs even for massless neutrinos
Calculation of atmospheric neutrino flux using the interaction model calibrated with atmospheric muon data
Using the ``modified DPMJET-III'' model explained in the previous paper, we
calculate the atmospheric neutrino flux. The calculation scheme is almost the
same as HKKM04 \cite{HKKM2004}, but the usage of the ``virtual detector'' is
improved to reduce the error due to it. Then we study the uncertainty of the
calculated atmospheric neutrino flux summarizing the uncertainties of
individual components of the simulation. The uncertainty of -production in
the interaction model is estimated by modifying FLUKA'97 and Fritiof 7.02 so
that they also reproduce the atmospheric muon flux data correctly, and the
calculation of the atmospheric neutrino flux with those modified interaction
models. The uncertainties of the flux ratio and zenith angle dependence of the
atmospheric neutrino flux are also studied
First-Principles Study of Electronic Structure in -(BEDT-TTF)I at Ambient Pressure and with Uniaxial Strain
Within the framework of the density functional theory, we calculate the
electronic structure of -(BEDT-TTF)I at 8K and room temperature
at ambient pressure and with uniaxial strain along the - and -axes. We
confirm the existence of anisotropic Dirac cone dispersion near the chemical
potential. We also extract the orthogonal tight-binding parameters to analyze
physical properties. An investigation of the electronic structure near the
chemical potential clarifies that effects of uniaxial strain along the a-axis
is different from that along the b-axis. The carrier densities show
dependence at low temperatures, which may explain the experimental findings not
only qualitatively but also quantitatively.Comment: 10 pages, 7 figure
Astrophysical Neutrino Telescopes
This review describes telescopes designed to study neutrinos from
astrophysical sources. These sources include the Sun and Supernovae emitting
neutrino energies up to tens of MeV, atmospheric neutrino sources caused by
cosmic ray interactions and other sources generating neutrino energies ranging
up to eV. Measurements with these telescopes also provide
information on neutrino properties including clear evidence for neutrino flavor
change. Telescopes in operation in the past and present are described, along
with plans for future instruments to expand this rapidly growing field of
particle astrophysics.Comment: 28 pages, 31 figures, Invited review article submitted to Review of
Scientific Instruments May 19, 200
Photoelectrochemical properties of plasma-induced nanostructured tungsten oxide
Helium (He)-induced nanostructured tungsten sheets were synthesized by He plasma irradiation under different plasma exposure durations. After calcination, nanostructured tungsten oxide samples were used as photoelectrodes to test photoelectrochemical (PEC) performance. The results showed that nanostructured WO3 photoanodes have higher PEC performance compared to the sample without nanostructures. The 15 min irradiated sample had the highest photocurrent density of 3.5 mA/cm2 under the thermodynamic potential of water oxidation (1.23 V vs. RHE). It was found that the oxide layer thickness and exposed crystal facet have a significant impact on PEC performance. The plasma synthesis technique has proved to be an effective method for preparing nanostructured WO3 photoelectrodes.</p
Tilted-Cone Induced Cusps and Nonmonotonic Structures in Dynamical Polarization Function of Massless Dirac Fermions
The polarization function of electrons with the tilted Dirac cone found in
organic conductors is studied using the tilted Weyl equation. The dynamical
property is explored based on the analytical treatment of the particle-hole
excitation. It is shown that the polarization function as the function of both
the frequency and the momentum exhibits cusps and nonmonotonic structures. The
polarization function depends not only on the magnitude but also the direction
of the external momentum. These properties are characteristic of the tilted
Dirac cone, and are contrast to the isotropic case of grapheme. Further, the
results are applied to calculate the optical conductivity, the plasma frequency
and the screening of Coulomb interaction, which are also strongly influenced by
the tilted cone.Comment: 28 pages, 12 figures, to be published in Journal of the Physical
Society of Japan Vol. 79 (2010) No. 1
Global fits to neutrino oscillation data
I summarize the determination of neutrino oscillation parameters within the
three-flavor framework from world neutrino oscillation data with date of May
2006, including the first results from the MINOS long-baseline experiment. It
is illustrated how the determination of the leading "solar" and "atmospheric"
parameters, as well as the bound on emerge from an interplay of
various complementary data sets. Furthermore, I discuss possible implications
of sub-leading three-flavor effects in present atmospheric neutrino data
induced by and for the bound on
and non-maximal values of , emphasizing, however, that these
effects are not statistically significant at present. Finally, in view of the
upcoming MiniBooNE results I briefly comment on the problem to reconcile the
LSND signal.Comment: 5 pages, 5 figures, talk presented at the SNOW2006 workshop,
Stockholm, 2-6 May 200
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