4,754 research outputs found
Tau polarization effects in the CNGS tau-neutrino appearance experiments
We studied tau polarization effects on the decay distributions of tau
produced in the CNGS tau-neutrino appearance experiments. We show that energy
and angular distributions for the decay products in the laboratory frame are
significantly affected by the tau polarization. Rather strong azimuthal
asymmetry about the tau momentum axis is predicted, which may have observable
consequences in experiments even with small statistics.Comment: 5 pages, 6 eps figures, espcrc2.sty; Proceedings of the 4th
International Workshop on Neutrino-Nucleus Interactions in the Few GeV Region
(NuInt05), September 26-29, 2005, Okayama, Japa
Pseudoscalar Form Factors in Tau-Neutrino Nucleon Scattering
We investigate the pseudoscalar transition form factors of nucleon for
quasi-elastic scattering and \Delta resonance production in tau-neutrino
nucleon scattering via the charged current interactions. Although the
pseudoscalar form factors play an important role for the \tau production in
neutrino-nucleon scattering, these are not known well. In this article, we
examine their effects in quasi-elastic scattering and \Delta resonance
production and find that the cross section, Q^{2} distribution, and spin
polarization of the produced \tau^{\pm} leptons are quite sensitive to the
pseudoscalar form factors.Comment: 7 pages, 3 figure
Polarization effects in tau production by neutrino
We studied polarization effects in tau production by neutrino-nucleon
scattering. Quasi-elastic scattering, resonance production and deep
inelastic scattering processes are taken into account for the CERN-to-Gran
Sasso projects. We show that the tau produced by neutrino has high degree of
polarization, and its spin direction depends non-trivially on the energy and
the scattering angle of tau in the laboratory frame.Comment: 6 pages, 5 eps figures, espcrc2.sty; Proceedings of the 3rd
International Workshop on Neutrino-Nucleus Interactions in the Few GeV Region
(NuInt04), March 17-21, 2004, Gran Sasso, Italy; minor changes, typos in Eq.
(6) correcte
Energy diffusion in frustrated quantum spin chains exhibiting Gaussian orthogonal ensemble level statistics
Frustrated quantum spin chains with the next-nearest-neighbor (NNN)
couplings are typically deterministic many-body systems exhibiting Gaussian
orthogonal ensemble (GOE) spectral statistics. We investigate energy diffusion
for these spin chains in the presence of a periodically oscillating magnetic
field. Diffusion coefficients are found to obey the power law with respect to
both the field strength and driving frequency with its power varying depending
on the linear response and non-perturbative regimes. The widths of the linear
response and the non-perturbative regimes depend on the strength of
frustrations. We have also elucidated a mechanism for oscillation of energy
diffusion in the case of weakened frustrations.Comment: 6 pages, 6 figure
VLBI study of water maser emission in the Seyfert 2 galaxy NGC5793. I: Imaging blueshifted emission and the parsec-scale jet
We present the first result of VLBI observations of the blueshifted water
maser emission from the type 2 Seyfert galaxy NGC5793, which we combine with
new and previous VLBI observations of continuum emission at 1.7, 5.0, 8.4, 15,
and 22 GHz. Maser emission was detected earlier in single-dish observations and
found to have both red- and blueshifted features relative to the systemic
velocity. We could image only the blueshifted emission, which is located 3.6 pc
southwest of the 22 GHz continuum peak. The blueshifted emission was found to
originate in two clusters that are separated by 0.7 milliarcsecond (0.16 pc).
No compact continuum emission was found within 3.6 pc of the maser spot. A
compact continuum source showing a marginally inverted spectrum between 1.7 and
5.0 GHz was found 4.2 pc southwest of the maser position. The spectral turnover
might be due to synchrotron self-absorption caused by a shock in the jet owing
to collision with dense gas, or it might be due to free-free absorption in an
ionized screen possibly the inner part of a disk, foreground to the jet.
The water maser may be part of a maser disk. If so, it would be rotating in
the opposite sense to the highly inclined galactic disk observed in CO
emission. We estimate a binding mass within 1 pc of the presumed nucleus to be
on the order of 10^7 Msun. Alternatively, the maser emission could result from
the amplification of a radio jet by foreground circumnuclear molecular gas. In
this case, the high blueshift of the maser emission might mean that the masing
region is moving outward away from the molecular gas surrounding an active
nucleus.Comment: 20 pages, 6 figures, to appear in ApJ, Oct. 200
Study on successive superconducting transitions in TaSC from electrical resistivity and nonlinear AC magnetic susceptibility
TaSC compound undergoes superconducting transitions at K and K. The nature of successive
superconducting transitions has been studied from electrical resistivity,
linear and nonlinear AC magnetic susceptibilities. The resistivity at
= 0 shows a local maximum near , a kink-like behavior around
, and reduces to zero at below = 2.1 K. The dependence
of is observed at = 50 kOe at low temperatures, which is due to
two-dimensional weak-localization effect. Below a two-dimensional
superconducting phase occurs in each TaC layer. The linear and nonlinear
susceptibilities , ,
, and as well as the difference
() between the FC and ZFC
susceptibilities, start to appear below 6.0 K, the onset temperature of
irreversibility. A drastic growth of the in-plane superconducting coherence
length below 6.0 K gives rise to a three-dimensional superconducting phase
below , through interplanar Josephson couplings between adjacent TaC
layers. The oscillatory behavior of ,
, and below is
related to the nonlinear behavior arising from the thermally activated flux
flow.Comment: 11 pages, 10 figures, Physical Review B (accepted for publication
Tau Polarization in Tau-Neutrino Nucleon Scattering
We investigate the spin polarization of \tau^{\pm} leptons produced in
\nu_{\tau} and \bar{\nu}_{\tau} nucleon scattering via charged currents.
Quasi-elastic scattering, \Delta resonance production and deep inelastic
scattering processes are studied. The polarization information is essential for
measuring the \tau^{\pm} appearance rate in long baseline neutrino oscillation
experiments, because the decay particle distributions depend crucially on the
\tau^{\pm} spin. In this article, we calculate the spin density matrix of each
process and estimate the spin polarization vector in medium and high neutrino
energy interactions. We find that the produced \tau^{\pm}'s have high degree of
polarization, and their spin direction depends non-trivially on the energy and
the scattering angle of \tau^{\pm} in the laboratory frame.Comment: 23 pages, 35 figures; compile errors corrected; notation errors in
Eq.(30) and (31) corrected, typo error in Eq.(40) corrected, references and
comments in footnote adde
Spin-orbital gap of multiorbital antiferromagnet
In order to discuss the spin-gap formation in a multiorbital system, we
analyze an e_g-orbital Hubbard model on a geometrically frustrated zigzag chain
by using a density-matrix renormalization group method. Due to the appearance
of a ferro-orbital arrangement, the system is regarded as a one-orbital system,
while the degree of spin frustration is controlled by the spatial anisotropy of
the orbital. In the region of strong spin frustration, we observe a finite
energy gap between ground and first-excited states, which should be called a
spin-orbital gap. The physical meaning is clarified by an effective Heisenberg
spin model including correctly the effect of the orbital arrangement influenced
by the spin excitation.Comment: 8 pages, 6 figures, extended versio
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