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, $Delta$ 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 $XXZ$ 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 Ta2_{2}S2_{2}C from electrical resistivity and nonlinear AC magnetic susceptibility

Ta$_{2}$S$_{2}$C compound undergoes superconducting transitions at $T_{cl} = 3.60 \pm 0.02$ K and $T_{cu} = 9.0 \pm 0.2$ K. The nature of successive superconducting transitions has been studied from electrical resistivity, linear and nonlinear AC magnetic susceptibilities. The resistivity $\rho$ at $H$ = 0 shows a local maximum near $T_{cu}$, a kink-like behavior around $T_{cl}$, and reduces to zero at below $T_{0}$ = 2.1 K. The $\ln T$ dependence of $\rho$ is observed at $H$ = 50 kOe at low temperatures, which is due to two-dimensional weak-localization effect. Below $T_{cu}$ a two-dimensional superconducting phase occurs in each TaC layer. The linear and nonlinear susceptibilities $\chi_{1}^{\prime\prime}$, $\chi_{3}^{\prime}$, $\chi_{5}^{\prime}$, and $\chi_{7}^{\prime}$ as well as the difference $\delta\chi$ ($= \chi_{FC} - \chi_{ZFC}$) 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 $T_{cl}$, through interplanar Josephson couplings between adjacent TaC layers. The oscillatory behavior of $\chi_{3}^{\prime\prime}$, $\chi_{5}^{\prime\prime}$, and $\chi_{7}^{\prime\prime}$ below $T_{cl}$ 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