JSNS
2
(J-PARC Sterile Neutrino Search at J-PARC Spallation Neutron Source) is an experiment that searches for sterile neutrinos via the observation of
ν
¯
μ
→
ν
¯
e
appearance oscillations using ...muon decay-at-rest neutrinos. The JSNS
2
experiment performed data taking from 2021. In this manuscript, a study of the accidental background is presented. The rate of the accidental background is (
9.29
±
0.39
)
×
10
-
8
/spill with 0.75 MW beam power and comparable to the expected number of signal events.
The gamman-->K(+)K(-)n reaction on 12C has been studied by measuring both K+ and K- at forward angles. A sharp baryon resonance peak was observed at 1.54+/-0.01 GeV/c(2) with a width smaller than 25 ...MeV/c(2) and a Gaussian significance of 4.6sigma. The strangeness quantum number (S) of the baryon resonance is +1. It can be interpreted as a molecular meson-baryon resonance or alternatively as an exotic five-quark state (uuddsmacr;) that decays into a K+ and a neutron. The resonance is consistent with the lowest member of an antidecuplet of baryons predicted by the chiral soliton model.
JSNS
2
(J-PARC Sterile Neutrino Search at J-PARC Spallation Neutron Source) is an experiment that is searching for sterile neutrinos via the observation of
ν
¯
μ
→
ν
¯
e
appearance oscillations ...using muon decay-at-rest neutrinos. Before dedicated data taking in the first-half of 2021, we performed a commissioning run for 10 days in June 2020. Using the data obtained in this commissioning run, in this paper, we present an estimate of the correlated background which imitates the
ν
¯
e
signal in a sterile neutrino search. In addition, in order to demonstrate future prospects of the JSNS
2
experiment, possible pulse shape discrimination improvements towards reducing cosmic ray induced fast neutron background are described.
Abstract
JSNS
$$^2$$
2
(J-PARC Sterile Neutrino Search at J-PARC Spallation Neutron Source) is an experiment that is searching for sterile neutrinos via the observation of
$${\bar{\nu }}_{\mu } ...\rightarrow {\bar{\nu }}_{e}$$
ν
¯
μ
→
ν
¯
e
appearance oscillations using muon decay-at-rest neutrinos. Before dedicated data taking in the first-half of 2021, we performed a commissioning run for 10 days in June 2020. Using the data obtained in this commissioning run, in this paper, we present an estimate of the correlated background which imitates the
$${\bar{\nu }}_{e}$$
ν
¯
e
signal in a sterile neutrino search. In addition, in order to demonstrate future prospects of the JSNS
$$^2$$
2
experiment, possible pulse shape discrimination improvements towards reducing cosmic ray induced fast neutron background are described.
The ϕ-Λ(1520) interference effect in the γp→K^{+}K^{-}p reaction has been measured for the first time in the energy range from 1.673 to 2.173 GeV. The relative phases between ϕ and Λ(1520) production ...amplitudes were obtained in the kinematic region where the two resonances overlap. The measurement results support strong constructive interference when K^{+}K^{-} pairs are observed at forward angles but destructive interference for proton emission at forward angles. Furthermore, the observed interference effect does not account for the sqrts=2.1 GeV bump structure in forward differential cross sections for ϕ photoproduction. This fact suggests possible exotic structures such as a hidden-strangeness pentaquark state, a new Pomeron exchange, or rescattering processes via other hyperon states.
We have proposed an experiment for studying charmed baryons via the p( pi super(-),D super(*-))p( pi -,D*-) reaction at the J-PARC high-momentum beam line. Charmed baryons will be measured by a ...missing mass method. Scattered D super(*-)D*- will be reconstructed by detecting its decay chain of D*- arrow right Dmacr0 pi - arrow right K+ pi - pi -. We designed a Ring Imaging Cherenkov (RICH) counter with two radiators, aerogel and C sub(4)F sub(10)C4F10 of refractive indices 1.04 and 1.00137, respectively, in order to identify pions and kaons in a wide momentum range from 2 to 16 GeV/c . Spherical mirrors will be used to focus Cherenkov photons to the photon sensor alloys. The performance of the designed RICH counter is evaluated by a Monte-Carlo simulation based on GEANT4. Detection efficiency for scattered particles averaged over pi and K is found to be 99%. Wrong particle identification ratios of pions and protons to kaons are 0.1% and 0.14%, respectively. The background level in the inclusive p( pi super(-),D super(*-))p( pi -,D*-) spectrum increases only 5% due to the wrong identifications.
The three-dimensional shape information of teeth provides useful information. However, obtaining accurate three-dimensional shapes of teeth is difficult without extracting them physically. In this ...study, we aimed to develop a method for automatically extracting accurate three-dimensional shapes of teeth from dental CT images.
The proposed method includes pre-processing and region extraction. Pre-processing is a combination of image-processing techniques that enhances tooth regions. In the region-extraction process, the region-growing method is introduced for extracting a region of each tooth. Constraint conditions determined by considering the characteristics of the structure of teeth are introduced for accurate extraction. Finally, morphological image processing is applied for eliminating discontinuous points.
We carried out an experiment in which the three-dimensional shapes of teeth were reconstructed from dental CT images. Quantitative evaluation was performed by measuring the three-dimensional spatial accordance rates between the region obtained by the proposed method and the manually extracted region. The proposed method was significantly more accurate than an existing method at the 5% level.
The experimental results showed that the proposed method reconstructs the shapes of teeth with high precision. However, an unextracted region remained at the surface of the enamel. Solving this problem and improving the extraction accuracy are important topics for future work.
The photo-production of ϕ mesons from Li, C, Al, and Cu at forward angles has been measured at Eγ=1.5–2.4GeV. The number of events for incoherent ϕ photo-production is found to have a target mass ...number dependence of A0.72±0.07 in the kinematical region of |t|⩽0.6GeV2/c2. The total cross section of the ϕ–nucleon interaction, σϕN, has been estimated as 35−11+17mb using the A-dependence of the ϕ photo-production yield and a Glauber-type multiple scattering theory. This value is much larger than σϕN in free space, suggesting that the ϕ properties might change in the nuclear medium.
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