67 research outputs found
A method to measure the quenching factor for recoil energy of oxygen in bismuth germanium oxide scintillators
Bismuth germanium oxide (, BGO) scintillation
crystals are widely used as detectors in the fields of particle physics and
astrophysics due to their high density, and thus higher efficiency for
gamma-ray detection. Owing to their good chemical stability, they can be used
in any environment. For rare-event searches, such as dark matter and coherent
elastic neutrino-nucleus scattering, BGO crystals are essential to comprehend
the response of nuclear recoil. In this study, we have analyzed the events of
neutron elastic scattering with oxygen in BGO crystals. Then, we have measured
the quenching factor for oxygen recoil energy in the BGO crystal as a function
of recoil energy by using a monoenergetic neutron source.Comment: 14 pages, 11 figures, 1 tabl
VLBI Monitoring Observations of Water Masers Around the Semi-Regular Variable Star R Crateris
We monitored water-vapor masers around the semi-regular variable star R
Crateris with the Japanese VLBI Network (J-Net) at the 22 GHz band during four
epochs with intervals of one month. The relative proper motions and
Doppler-velocity drifts of twelve maser features were measured. Most of them
existed for longer than 80 days. The 3-D kinematics of the features indicates a
bipolar expanding flow. The major axis of the asymmetric flow was estimated to
be at P.A. = 136 degrees. The existence of a bipolar outflow suggests that a
Mira variable star had already formed a bipolar outflow. The water masers are
in a region of apparent minimum radii of 1.3 x 10^12 m and maximum radii of 2.6
x 10^12 m, between which the expansion velocity ranges from 4.3 to 7.4 km/s.
These values suggest that the water masers are radially accelerated, but still
gravitationally bound, in the water-maser region. The most positive and
negative velocity-drifting features were found relatively close to the systemic
velocity of the star. We found that the blue-shifted features are apparently
accelerated and the red-shifted apparently decelerated. The acceleration of
only the blue-shifted features seems to be consistent with that of the
expanding flow from the star.Comment: 15 pages, 5 figures, Accepted for publication in PASJ (2001),
preprint can be obtained via WWW on
http://www.nro.nao.ac.jp/library/report/list.htm
Resolving Neutrino Mass Hierarchy and CP Degeneracy by Two Identical Detectors with Different Baselines
We explore the possibility of simultaneous determination of neutrino mass
hierarchy and the CP violating phase by using two identical detectors placed at
different baseline distances. We focus on a possible experimental setup using
neutrino beam from J-PARC facility in Japan with beam power of 4MW and megaton
(Mton)-class water Cherenkov detectors, one placed in Kamioka and the other at
somewhere in Korea. We demonstrate, under reasonable assumptions of systematic
uncertainties, that the two-detector complex with each fiducial volume of 0.27
Mton has potential of resolving neutrino mass hierarchy up to sin^2 2theta_{13}
> 0.03 (0.055) at 2\sigma (3\sigma) CL for any values of delta and at the same
time has the sensitivity to CP violation by 4 + 4 years running of nu_e and
nu_e-bar appearance measurement. The significantly enhanced sensitivity is due
to clean detection of modulation of neutrino energy spectrum, which is enabled
by cancellation of systematic uncertainties between two identical detectors
which receive the neutrino beam with the same energy spectrum in the absence of
oscillations.Comment: 23 pages, 10 figures, version published in PR
Identification of intracellular squalene in living algae, Aurantiochytrium mangrovei with hyper-spectral coherent anti-Stokes Raman microscopy using a sub-nanosecond supercontinuum laser source
We applied hyper-spectral coherent anti-Stokes Raman scattering imaging to intracellular lipid identification in living microalgae, Aurantiochytrium mangrovei 18W-13a. Two different lipids, squalene and triacylglycerol, were found inside living cells with clear vibrational contrast. Based on the endogenous lipid band as a result of the cis C[DOUBLE BOND]C stretch vibrational mode, squalene and triacylglycerol were clearly distinguished in different intracellular areas. In particular, squalene was detected solely in vacuoles as lipid particles, which was also supported by electron microscopy
Current status of Japanese detectors
Current status of TAMA and CLIO detectors in Japan is reported in this
article. These two interferometric gravitational-wave detectors are being
developed for the large cryogenic gravitational wave telescope (LCGT) which is
a future plan for detecting gravitational wave signals at least once per year.
TAMA300 is being upgraded to improve the sensitivity in low frequency region
after the last observation experiment in 2004. To reduce the seismic noises, we
are installing new seismic isolation system, which is called TAMA Seismic
Attenuation System, for the four test masses. We confirmed stable mass locks of
a cavity and improvements of length and angular fluctuations by using two SASs.
We are currently optimizing the performance of the third and fourth SASs. We
continue TAMA300 operation and R&D studies for LCGT. Next data taking in the
summer of 2007 is planned.
CLIO is a 100-m baseline length prototype detector for LCGT to investigate
interferometer performance in cryogenic condition. The key features of CLIO are
that it locates Kamioka underground site for low seismic noise level, and
adopts cryogenic Sapphire mirrors for low thermal noise level. The first
operation of the cryogenic interferometer was successfully demonstrated in
February of 2006. Current sensitivity at room temperature is close to the
target sensitivity within a factor of 4. Several observation experiments at
room temperature have been done. Once the displacement noise reaches at thermal
noise level of room temperature, its improvement by cooling test mass mirrors
should be demonstrated.Comment: 6 pages, 5 figures, Proceedings of GWDAW-1
\mu-\tau Symmetry and Maximal CP Violation
We argue the possibility that a real part of a flavor neutrino mass matrix
only respects a mu-tau symmetry. This possibility is shown to be extended to
more general case with a phase parameter \theta, where the mu-tau symmetric
part has a phase of \theta/2. This texture shows maximal CP violation and no
Majorana CP violation.Comment: 5 pages, version to appear in Phys. Lett.
SHG-specificity of cellular Rootletin filaments enables naĂŻve imaging with universal conservation
Despite growing demand for truly naĂŻve imaging, label-free observation of cilium-related structure remains challenging, and validation of the pertinent molecules is correspondingly difficult. In this study, in retinas and cultured cells, we distinctively visualized Rootletin filaments in rootlets in the second harmonic generation (SHG) channel, integrated in custom coherent nonlinear optical microscopy (CNOM) with a simple, compact, and ultra-broadband supercontinuum light source. This SHG signal was primarily detected on rootlets of connecting cilia in the retinal photoreceptor and was validated by colocalization with anti-Rootletin staining. Transfection of cells with Rootletin fragments revealed that the SHG signal can be ascribed to filaments assembled from the R234 domain, but not to cross-striations assembled from the R123 domain. Consistent with this, Rootletin-depleted cells lacked SHG signal expected as centrosome linker. As a proof of concept, we confirmed that similar fibrous SHG was observed even in unicellular ciliates. These findings have potential for broad applications in clinical diagnosis and biophysical experiments with various organisms
Determination of Neutrino Mass Texture for Maximal CP Violation
We show a general form of neutrino mass matrix (M), whose matrix elements are
denoted by M_{ij} (i.j=e, mu, tau) as flavor neutrino masses, that induces
maximal CP violation as well as maximal atmospheric neutrino mixing. The masses
of M_{mu mu}, M_{tau tau} and M_{mu tau}+sigma M_{ee} (sigma =\pm 1) turn out
to be completely determined by M_{e mu} and M_{e tau} for given mixing angles.
The appearance of CP violation is found to originate from the interference
between the mu-tau symmetric part of M and its breaking part. If |M_{e
mu}|=|M_{e tau}|, giving either M_{e mu}=-sigma e^{i theta} M_{e tau} or M_{e
mu}=-sigma e^{i theta}M*_{e tau} with a phase parameter theta, is further
imposed, we find that |M_{mu mu}|=|M_{tau tau}|is also satisfied. These two
constraints can be regarded as an extended version of the constraints in the
mu-tau symmetric texture given by M_{e mu}=-sigma M_{e tau} and M_{mu
mu}=M_{tau tau}. Majorana CP violation becomes active if arg(M_{mu tau})\neq
arg(M_{e mu})+theta/2 for M_{e mu}=-sigma e^{i theta} M_{e tau} and if
arg(M_{mu tau})\neq theta/2 for M_{e mu}=-sigma e^{i theta} M*_{e tau}.Comment: 10 pages, RevTex, typos corrected, minor clarifications added in
Sec.3 and Sec.4, version to appear in Nucl. Phys.
Coincidence analysis to search for inspiraling compact binaries using TAMA300 and LISM data
Japanese laser interferometric gravitational wave detectors, TAMA300 and
LISM, performed a coincident observation during 2001. We perform a coincidence
analysis to search for inspiraling compact binaries. The length of data used
for the coincidence analysis is 275 hours when both TAMA300 and LISM detectors
are operated simultaneously. TAMA300 and LISM data are analyzed by matched
filtering, and candidates for gravitational wave events are obtained. If there
is a true gravitational wave signal, it should appear in both data of detectors
with consistent waveforms characterized by masses of stars, amplitude of the
signal, the coalescence time and so on. We introduce a set of coincidence
conditions of the parameters, and search for coincident events. This procedure
reduces the number of fake events considerably, by a factor
compared with the number of fake events in single detector analysis. We find
that the number of events after imposing the coincidence conditions is
consistent with the number of accidental coincidences produced purely by noise.
We thus find no evidence of gravitational wave signals. We obtain an upper
limit of 0.046 /hours (CL ) to the Galactic event rate within 1kpc from
the Earth. The method used in this paper can be applied straightforwardly to
the case of coincidence observations with more than two detectors with
arbitrary arm directions.Comment: 28 pages, 17 figures, Replaced with the version to be published in
Physical Review
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