4,007 research outputs found
Precision Measurement of the Position-space Wave Functions of Gravitationally Bound Ultracold Neutrons
Gravity is the most familiar force at our natural length scale. However, it
is still exotic from the view point of particle physics. The first experimental
study of quantum effects under gravity was performed using a cold neutron beam
in 1975. Following this, an investigation of gravitationally bound quantum
states using ultracold neutrons was started in 2002. This quantum bound system
is now well understood, and one can use it as a tunable tool to probe gravity.
In this paper, we review a recent measurement of position-space wave functions
of such gravitationally bound states, and discuss issues related to this
analysis, such as neutron loss models in a thin neutron guide, the formulation
of phase space quantum mechanics, and UCN position sensitive detectors. The
quantum modulation of neutron bound states measured in this experiment shows
good agreement with the prediction from quantum mechanics.Comment: 13 pages, 5 figure
Magnetic field-induced deformation of the spin-density wave microphases in CaCoO
The frustrated triangular Ising magnet CaCoO has long been known
for an intriguing combination of extremely slow spin dynamics and peculiar
magnetic orders, such as the evenly-spaced non-equilibrium metamagnetic
magnetization steps and the long-wavelength spin density wave (SDW) order, the
latter of which is essentially an emergent crystal of solitons. Recently, an
elaborate field-cooling protocol to bypass the low-field SDW phase was proposed
to overcome the extraordinarily long timescale of spin relaxation that impeded
previous experimental studies in equilibrium, which may point to a deep
connection between the low-temperature slow relaxation and the cooling process
passing through the low-field SDW phase. As the first step to elucidate the
conjectured connection, we investigate the magnetic field-induced deformation
of the SDW state and incommensurate-commensurate transitions, thereby mapping
out the equilibrium in-field phase diagram for a realistic three-dimensional
lattice spin model by using Monte Carlo simulations. We also discuss
Ginzburg-Landau theory that includes several Umklapp terms as well as an
effective sine-Gordon model, which can qualitatively explain the observed
magnetic field-induced deformation of the SDW microphases.Comment: 9 pages, 5 figure
The Nagoya cosmic-ray muon spectrometer 3, part 2: Track detector
The twelve wide gap spark chambers were utilized as the track detectors of the Nagoya cosmic-ray muon spectrometer not only to obtain the precise locations of particles, but also to get some information about the correspondences between segments of trajectories. The area of each chamber is 150 x 70 sq cm and the width of a gap is 5 cm. The gas used is He at the atmospheric pressure. Each three pairs of them are placed on both sides of the deflection magnet. All images of sparks for each event are projected through the mirror system and recorded by two cameras stereoscopically. The mean detection efficiency of each chamber is 95 + or - 2% and the spacial resolution (jitter and drift) obtained from the prototype-experiment is 0.12 mm. Maximum detectable momentum of the spectrometer is estimated at about 10 TeV/c taking into account these characteristics together with the effects of the energy loss and multiple Coulomb scattering of muons in the iron magnet
Angular and Abundance Distribution of High-energy Gamma Rays and Neutrons Simulated by GEANT4 Code for Solar Flares
In the solar flare observed on June 3, 2012, high energy gamma-rays and
neutrons were observed. The event includes a remarkable feature of a high
neutron/gamma-ratio in the secondary particles. We have examined whether this
high n/-ratio can be explained by simulation. As a result of
simulations using the GEANT4 program, the high n/-ratio may be
reproduced for the case that helium and other heavy ions were dominantly
accelerated in the flare.Comment: submitted to the Proceeding of The 20th International Symposium on
Very High Energy Cosmic Ray Interaction (ISVHECRI 2018, Nagoya, Japan),
Europian Physics Journa
Monolithic Ge:Ga Detector Development for SAFARI
We describe the current status and the prospect for the development of
monolithic Ge:Ga array detector for SAFARI. Our goal is to develop a 64x64
array for the 45 -- 110 um band, on the basis of existing technologies to make
3x20 monolithic arrays for the AKARI satellite. For the AKARI detector we have
achieved a responsivity of 10 A/W and a read-out noise limited NEP (noise
equivalent power) of 10^-17 W/rHz. We plan to develop the detector for SAFARI
with technical improvements; significantly reduced read-out noise with newly
developed cold read-out electronics, mitigated spectral fringes as well as
optical cross-talks with a multi-layer antireflection coat. Since most of the
elemental technologies to fabricate the detector are flight-proven, high
technical readiness levels (TRLs) should be achieved for fabricating the
detector with the above mentioned technical demonstrations. We demonstrate some
of these elemental technologies showing results of measurements for test
coatings and prototype arrays.Comment: To appear in Proc. Workshop "The Space Infrared Telescope for
Cosmology & Astrophysics: Revealing the Origins of Planets and Galaxies".
Eds. A.M. Heras, B. Swinyard, K. Isaak, and J.R. Goicoeche
Multiferroic behavior in trimerized Mott insulators
We demonstrate multiferroic behavior in trimerized Mott insulators through
interplay between spins and electric dipole moments resulting from electronic
charge fluctuations in frustrated units. The model consists of stacked
triangular layers of trimers with small intertrimer exchange interactions
and . Ferroelectric states coexist with ferro- or antiferromagnetic
orderings depending on the value of the magnetic field and the sign of the
interlayer exchange . The electric polarization undergoes abrupt changes as
a function of .Comment: 5 pages, 2 figures; published in Phys. Rev. Let
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