329 research outputs found
Performance of Multi-Pixel Photon Counters for the T2K near detectors
We have developed a Multi-Pixel Photon Counter (MPPC) for the neutrino
detectors of T2K experiment. About 64,000 MPPCs have been produced and tested
in about a year. In order to characterize a large number of MPPCs, we have
developed a system that simultaneously measures 64 MPPCs with various bias
voltage and temperature. The performance of MPPCs are found to satisfy the
requirement of T2K experiment. In this paper, we present the performance of
17,686 MPPCs measured at Kyoto University.Comment: 15 pages, 14 figure
Angle-resolved photoemission spectroscopy of Co-based boride superconductor LaCo1.73Fe0.27B2
We have performed angle-resolved photoemission spectroscopy of Co-based
boride superconductor LaCo1.73Fe0.27B2 (Tc = 4.1 K), which is isostructural to
the 122-type Fe-pnictide superconductor with the pnictogen atom being replaced
with boron. We found that the Fermi level is located at a dip in the density of
states (DOS) in contrast to Co-pnictide ferromagnets. This reduction in DOS
together with the strong Co 3d-B 2p covalent bonding removes the ferromagnetic
order and may cause the superconductivity. The energy bands near the Fermi
level show higher three dimensionality and a weaker electron-correlation effect
than those of Fe pnictides. The Fermi surface topology is considerably
different from that of Fe pnictides, suggesting the difference in the
superconducting mechanism between boride and pnictide superconductors.Comment: 5 pages, 4 figure
ARPES observation of isotropic superconducting gaps in isovalent Ru-substituted Ba(FeRu)As
We used high-energy resolution angle-resolved photoemission spectroscopy to
extract the momentum dependence of the superconducting gap of Ru-substituted
Ba(FeRu)As ( K). Despite a strong
out-of-plane warping of the Fermi surface, the magnitude of the superconducting
gap observed experimentally is nearly isotropic and independent of the
out-of-plane momentum. More precisely, we respectively observed 5.7 meV and 4.5
meV superconducting gaps on the inner and outer -centered hole Fermi
surface pockets, whereas a 4.8 meV gap is recorded on the M-centered electron
Fermi surface pockets. Our results are consistent with the model with
a dominant antiferromagnetic exchange interaction between the next-nearest Fe
neighbors.Comment: 5 pages, 4 figure
Search for Fragmented M1 Strength in 48-Ca
This research was sponsored by the National Science Foundation Grant NSF PHY-931478
The apparent Coulomb reacceleration of neutrons in electrodissociation of the deuteron
We demonstrate that the final state - interaction in the reaction of
electrodissociation of the deuteron at large in a static external field
leads to the apparent reacceleration of neutrons. The shift of the neutron
velocity from the velocity of the deuteron beam is related to the
quantum-mechanical forward-backward asymmetry of the missing momentum
distribution in the scattering.Comment: LATEX, 9 pages, 1 figure available from the authors on request,
Juelich preprint KFA-IKP(TH)-1994-3
A photogrammetric method for target monitoring inside the MEG II detector
An automatic target monitoring method based on photographs taken by a CMOS photo-camera has been developed for the MEG II detector. The technique could be adapted for other fixed-target experiments requiring good knowledge of their target position to avoid biases and systematic errors in measuring the trajectories of the outcoming particles. A CMOS-based, high resolution, high radiation tolerant, and high magnetic field resistant photo-camera was mounted inside the MEG II detector at the Paul Scherrer Institute (Switzerland). MEG II is used to search for lepton flavor violation in muon decays. The photogrammetric method’s challenges, affecting measurements of low momentum particles’ tracks, are the high magnetic field of the spectrometer, high radiation levels, tight space constraints, and the need to limit the material budget in the tracking volume. The camera is focused on the dot pattern drawn on the thin MEG II target, about 1 m away from the detector endcaps where the photo-camera is placed. Target movements and deformations are monitored by comparing images of the dots taken at various times during the measurement. The images are acquired with a Raspberry board and analyzed using custom software. Global alignment to the spectrometer is guaranteed by corner cubes placed on the target support. As a result, the target monitoring fulfills the needs of the experiment
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