205 research outputs found
Characterization of electrostatic shock in laser-produced optically-thin plasma flows using optical diagnostics
We present a method for evaluating the properties of electrostatic shock in laser-produced plasmas by using optical diagnostics. A shock is formed by a collimated jet in counter-streaming plasmas in nearly collisionless condition, showing the steepening of the transition width in time. In the present experiment, a streaked optical pyrometry was applied to evaluate the electron density and temperatures in the upstream and downstream regions of the shock so that the shock conditions are satisfied, by assuming thermal bremsstrahlung emission in optically thin plasmas. The derived electron densities are nearly consistent with those estimated from interferometry
Bond-disordered Anderson model on a two dimensional square lattice - chiral symmetry and restoration of one-parameter scaling
Bond-disordered Anderson model in two dimensions on a square lattice is
studied numerically near the band center by calculating density of states
(DoS), multifractal properties of eigenstates and the localization length. DoS
divergence at the band center is studied and compared with Gade's result [Nucl.
Phys. B 398, 499 (1993)] and the powerlaw. Although Gade's form describes
accurately DoS of finite size systems near the band-center, it fails to
describe the calculated part of DoS of the infinite system, and a new
expression is proposed. Study of the level spacing distributions reveals that
the state closest to the band center and the next one have different level
spacing distribution than the pairs of states away from the band center.
Multifractal properties of finite systems furthermore show that scaling of
eigenstates changes discontinuously near the band center. This unusual behavior
suggests the existence of a new divergent length scale, whose existence is
explained as the finite size manifestation of the band center critical point of
the infinite system, and the critical exponent of the correlation length is
calculated by a finite size scaling. Furthermore, study of scaling of Lyapunov
exponents of transfer matrices of long stripes indicates that for a long stripe
of any width there is an energy region around band center within which the
Lyapunov exponents cannot be described by one-parameter scaling. This region,
however, vanishes in the limit of the infinite square lattice when
one-parameter scaling is restored, and the scaling exponent calculated, in
agreement with the result of the finite size scaling analysis.Comment: 23 pages, 11 figures. RevTe
Transitions from the Quantum Hall State to the Anderson Insulator: Fa te of Delocalized States
Transitions between the quantum Hall state and the Anderson insulator are
studied in a two dimensional tight binding model with a uniform magnetic field
and a random potential. By the string (anyon) gauge, the weak magnetic field
regime is explored numerically. The regime is closely related to the continuum
model. The change of the Hall conductance and the trajectoy of the delocalized
states are investigated by the topological arguments and the Thouless number
study.Comment: 10 pages RevTeX, 14 postscript figure
Explicit Gauge Fixing for Degenerate Multiplets: A Generic Setup for Topological Orders
We supply basic tools for the study of the topological order of a multiplet
which is an eigenspace of a finite-dimensional normal operator with continuous
parameters. We allow intrinsic degeneracies within the multiplet where a
well-known standard procedure does not work. As an important example, we give
novel expressions for a spin Hall conductance for unitary superconductors with
equal spin pairing. Generic topological orders will be treated in this unified
manner particularly with nontrivial topological degeneracies.Comment: Almost final version. (Topological) Degeneracy is stresse
Search for Electron Neutrino Appearance in a 250 km Long-baseline Experiment
We present a search for electron neutrino appearance from accelerator
produced muon neutrinos in the K2K long baseline neutrino experiment. One
candidate event is found in the data corresponding to an exposure of 4.8*10^19
protons on target. The expected background in the absence of neutrino
oscillations is estimated to be 2.4+-0.6 events and is dominated by
mis-identification of events from neutral current pi^0 production. We exclude
the \nu_\mu to \nu_e oscillations at 90% C.L. for the effective mixing angle in
2-flavor approximation of sin^2(2theta_\mu_e) (~= 1/2 sin^2 2 th_13) > 0.15 at
Delta m^2_\mu_e = 2.8*10^{-3} eV^2, the best fit value of the \nu_\mu
disappearance analysis in K2K. The most stringent limit of sin^2(2theta_\mu_e)
< 0.09 is obtained at Delta m^2_\mu_e = 6*10^{-3} eV^2.Comment: 5 pages with 2 figures embeded in two column revtex4 style. Accepted
to be published in Phys. Rev. Let
The K2K SciBar Detector
A new near detector, SciBar, for the K2K long-baseline neutrino oscillation
expe riment was installed to improve the measurement of neutrino energy
spectrum and to study neutrino interactions in the energy region around 1 GeV.
SciBar is a 'fully active' tracking detector with fine segmentation consisting
of plastic scintillator bars. The detector was constructed in summer 2003 and
is taking data since October 2003. The basic design and initial performance is
presented.Comment: 7 pages, 4figures, Contributed to Proceedings of the 10th Vienna
Conference on Instrumentation, Vienna, February 16-21, 200
Measurement of single pi0 production in neutral current neutrino interactions with water by a 1.3 GeV wide band muon neutrino beam
Neutral current single pi0 production induced by neutrinos with a mean energy
of 1.3 GeV is measured at a 1000 ton water Cherenkov detector as a near
detector of the K2K long baseline neutrino experiment. The cross section for
this process relative to the total charged current cross section is measured to
be 0.064 +- 0.001 (stat.) +- 0.007 (sys.). The momentum distribution of
produced pi0s is measured and is found to be in good agreement with an
expectation from the present knowledge of the neutrino cross sections.Comment: 6 pages, 4 figures, Submitted to Phys. Lett.
Belle II Technical Design Report
The Belle detector at the KEKB electron-positron collider has collected
almost 1 billion Y(4S) events in its decade of operation. Super-KEKB, an
upgrade of KEKB is under construction, to increase the luminosity by two orders
of magnitude during a three-year shutdown, with an ultimate goal of 8E35 /cm^2
/s luminosity. To exploit the increased luminosity, an upgrade of the Belle
detector has been proposed. A new international collaboration Belle-II, is
being formed. The Technical Design Report presents physics motivation, basic
methods of the accelerator upgrade, as well as key improvements of the
detector.Comment: Edited by: Z. Dole\v{z}al and S. Un
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