Super-Kamiokande (SK) can search for weakly interacting massive particles (WIMPs) by detecting neutrinos produced from WIMP annihilations occurring inside the Sun. In this analysis, we include ...neutrino events with interaction vertices in the detector in addition to upward-going muons produced in the surrounding rock. Compared to the previous result, which used the upward-going muons only, the signal acceptances for light (few-GeV/c^{2}-200-GeV/c^{2}) WIMPs are significantly increased. We fit 3903 days of SK data to search for the contribution of neutrinos from WIMP annihilation in the Sun. We found no significant excess over expected atmospheric-neutrino background and the result is interpreted in terms of upper limits on WIMP-nucleon elastic scattering cross sections under different assumptions about the annihilation channel. We set the current best limits on the spin-dependent WIMP-proton cross section for WIMP masses below 200 GeV/c^{2} (at 10 GeV/c^{2}, 1.49×10^{-39} cm^{2} for χχ→bbover ¯ and 1.31×10^{-40} cm^{2} for χχ→τ^{+}τ^{-} annihilation channels), also ruling out some fraction of WIMP candidates with spin-independent coupling in the few-GeV/c^{2} mass range.
Although generally ascribed to the presence of defects, an ultimate assignment of the different contributions to the emission spectrum in terms of surface states and deep levels in ZnO nanostructures ...is still lacking. In this work we unambiguously give first evidence that zinc vacancies at the (1010) nonpolar surfaces are responsible for the green luminescence of ZnO nanostructures. The result is obtained by performing an exhaustive comparison between spatially resolved cathodoluminescence spectroscopy and imaging and ab initio simulations. Our findings are crucial to control undesired recombinations in nanostructured devices.
A comprehensive study of the atmospheric neutrino flux in the energy region from sub-GeV up to several TeV using the Super-Kamiokande (SK) water Cherenkov detector is presented in this paper. The ...energy and azimuthal spectra, and variation over time, of the atmospheric νe+ν¯e and νμ+ν¯μ fluxes are measured. The energy spectra are obtained using an iterative unfolding method by combining various event topologies with differing energy responses. The azimuthal spectra depending on energy and zenith angle, and their modulation by geomagnetic effects, are also studied. A predicted east-west asymmetry is observed in both the νe and νμ samples at 8.0σ and 6.0σ significance, respectively, and an indication that the asymmetry dipole angle changes depending on the zenith angle was seen at the 2.2σ level. The measured energy and azimuthal spectra are consistent with the current flux models within the estimated systematic uncertainties. A study of the long-term correlation between the atmospheric neutrino flux and the solar magnetic activity cycle is performed, and a weak preference for a correlation was seen at the 1.1σ level, using SK-I–SK-IV data spanning a 20-year period. For several particularly strong solar activity periods, corresponding to Forbush decrease events, no theoretical prediction is available but a deviation below the typical neutrino event rate is seen at the 2.4σ level. The seasonal modulation of the neutrino flux is also examined, but the change in flux at the SK site is predicted to be negligible, and, as expected, no evidence for a seasonal correlation is seen.
ZnO micropatterning under very mild conditions is presented. Photolysis (using a mask) of Si–C bonds in a self‐assembled phenylsilane layer yields a patterned phenyl/hydroxy surface. ZnO is ...selectively deposited at 55 °C on the phenyl domains by electroless deposition using a Pd catalyst adhered to the surface. The viability of the ZnO pattern as a phosphor is illustrated by the visible light cathodoluminescence image shown in the Figure and on the cover.
This paper presents the formation of complex cross-sectional microfibers using three-dimensional microfluidic devices. The compartments and shapes of core and shell layers in the microfibers were ...independently controlled
via
three-dimensional fluidic channels fabricated by the combination of sheath units. The number of layers is easily expanded by the stacking of these units. Therefore, the highly heterogeneous microfibers of alginate hydrogel are obtained in polydimethylsiloxane structures. This widely expandable method has great potential for the development of functional and complex fiber-shaped materials.
This paper presents the formation of complex cross-sectional microfibers using three-dimensional microfluidic devices.
The generation of polycrystalline grains region near the crucible wall during seeded growth of monocrystalline silicon in a unidirectional solidification furnace was analyzed numerically. The ...crystal–melt interface is tracked by an enthalpy method. Numerical results show that some polycrystalline silicon grains generates along the crucible wall and marches into the interior of crystal. The ratio of polycrystalline silicon grains in a global crystal is mainly determined by a ratio of thermal flux along the crucible wall to thermal flux along the seed. By reducing the thermal flux along the crucible wall or by increasing the thermal flux along the seed, the ratio of polycrystalline silicon grains in a global crystal can be markedly reduced.
► Seeded growth of monocrystalline silicon is simulated. ► Polycrystalline silicon grains near crucible wall can be reduced. ► Reducing thermal flux along crucible wall will reduce polycrystalline silicon grains. ► Increasing thermal flux along seed will also reduce grains' polycrystalline silicon.
We present a compact, vacuum compatible seismic attenuation system designed to isolate five auxiliary optical benches for Advanced Virgo, a second generation gravitational wave detector. We report on ...the design of the device, coined MultiSAS (multistage seismic attenuation system) and on its measured vibration isolation performance. The latter can be summarized by quoting a payload isolation ratio at 10 Hz of 100 dB and 140 dB in vertical and horizontal, respectively. We also present the design and performance of the MultiSAS control system along the translation degrees of freedom, as well as a discussion of the possible coupling to the angular degrees of freedom. Over a time-scale of 100 s, 1 m magnitude RMS for translational degrees of freedom is achieved for seismic conditions observed in the past five years at the Virgo site and in Amsterdam. The spectral displacement levels are expected to be lower than 10−14 m from 10 Hz onwards in vertical and horizontal. In addition we discuss effects that could deteriorate the performance of the device such as thermal drifts of the mechanical filters, residual acoustic coupling and cradle effects on the inverted pendulum pre-isolation stage. Mitigation strategies or solutions were devised and installed in the five Advanced Virgo systems.
In this study, the simple and rapid formation of porous silicon on a pillar array structure using inductively coupled plasma reactive ion etching (ICP-RIE) is realized. This method can render the ...outermost surface porous without using an additional etching or deposition apparatus because the same equipment is used to form the structure. As a basic experiment, we attempted to etch the structure by considerably varying three parameters (bias power, chamber pressure, and gas flow rate) in ICP-RIE. The etching step condition was determined for the porous structure from the result. Furthermore, we obtained a porous pillar surface while almost maintaining the structure by performing multicycle etching and an additional passivation step. A number of pores (diameter: ~100 nm) were formed randomly on the side wall of the pillar array using the proposed method. Compared with original pillar, the surface roughness of porous pillar increased by 48%. 2019-0216.
Calibration of the Super-Kamiokande detector Abe, K.; Iyogi, K.; Kameda, J. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
02/2014, Letnik:
737
Journal Article
Recenzirano
Odprti dostop
Procedures and results on hardware-level detector calibration in Super-Kamiokande (SK) are presented in this paper. In particular, we report improvements made in our calibration methods for the ...experimental phase IV in which new readout electronics have been operating since 2008.
The topics are separated into two parts. The first part describes the determination of constants needed to interpret the digitized output of our electronics so that we can obtain physical numbers such as photon counts and their arrival times for each photomultiplier tube (PMT). In this context, we developed an in situ procedure to determine high-voltage settings for PMTs in large detectors like SK, as well as a new method for measuring PMT quantum efficiency and gain in such a detector.
The second part describes modeling of the detector in Monte Carlo simulations, including, in particular, the optical properties of the water target and their variability over time. Detailed studies on water quality are also presented.
As a result of this work, we have achieved a precision sufficient for physics analyses over a wide energy range (from a few MeV to above 1TeV). For example, charge determination was at the level of 1%, and the timing resolution was 2.1ns at the one-photoelectron charge level and 0.5ns at the 100-photoelectron charge level.
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