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identification method by the 
reaction for a 
scattering experiment at J-PARC坂尾 珠和*; 藤田 真奈美; 長谷川 勝一; 細見 健二; 市川 真也; 市川 裕大; 今井 憲一*; 七村 拓野; 成木 恵; 佐甲 博之; et al.
JPS Conference Proceedings (Internet), 33, p.011133_1 - 011133_6, 2021/03
The reaction is an important elementary process to produce from a proton target and is a key for a scattering experiment where the momentum of should be tagged from the missing momentum of the 
reaction. However, the spectroscopy method has not been established yet due to the difficulty of the 
detection. Therefore, we have proposed a new detection method where 
and 
from the decay are measured by a forward magnetic spectrometer and a detector cluster surrounding the target, respectively. The feasibility of the detection method was confirmed by analyzing the J-PARC E40 data taken with such a detector system. In the analysis, 's were successfully identified in the missing mass spectrum of the 
reaction.
scattering experiment at J-PARC and the analysis status中田 祥之*; 長谷川 勝一; 早川 修平*; 細見 健二; 市川 裕大; 今井 憲一; 七村 拓野*; 成木 恵*; 佐甲 博之; 佐藤 進; et al.
JPS Conference Proceedings (Internet), 26, p.023024_1 - 023024_5, 2019/11
J-PARC E40 aims to measure the differential cross sections of the 
elastic scatterings and the 
conversion. A clear peak of 
was observed in a missing mass spectrum of the 
reaction and recoil protons from the 
elastic scattering were successfully observed in the data taken in the summer 2018. The rest of data taking is coming in the spring 2019.
Chambers, C.*; 伊藤 由太; nEXO Collaboration*; 他150名*
Nature, 569, p.203 - 207, 2019/05
被引用回数：34 パーセンタイル：84.09(Multidisciplinary Sciences)Double-
-decay involves the simultaneous conversion of two neutrons into two protons, and the emission of two electrons and two neutrinos; the neutrinoless process, although not yet observed, is thought to involve the emission of the two electrons but no neutrinos. The search for neutrinoless-double--decay probes fundamental properties of neutrinos, including whether or not the neutrino and antineutrino are distinct particles. Double--decay detectors are large and expensive, so it is essential to achieve the highest possible sensitivity with each study, and removing spurious contributions ("background") from detected signals is crucial. In the nEXO neutrinoless-double--decay experiment, the identification, or "tagging", of the 
Ba daughter atom resulting from the double-decay of Xe provides a technique for discriminating background. The tagging scheme studied here uses a cryogenic probe to trap the barium atom in a solid xenon matrix, where the barium atom is tagged through fluorescence imaging. Here we demonstrate the imaging and counting of individual barium atoms in solid xenon by scanning a focused laser across a solid xenon matrix deposited on a sapphire window. When the laser irradiates an individual atom, the fluorescence persists for about 30 seconds before dropping abruptly to the background level a clear confirmation of one-atom imaging. Following evaporation of a barium deposit, the residual barium fluorescence is 0.16 percent or less. Our technique achieves the imaging of single atoms in a solid noble element, establishing the basic principle of barium tagging for nEXO.
meson production in the forward/backward rapidity region in Cu + Au collisions at 
= 200 GeVAdare, A.*; 長谷川 勝一; 今井 憲一; 永宮 正治; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他505名*
Physical Review C, 93(2), p.024904_1 - 024904_13, 2016/02
被引用回数：14 パーセンタイル：62.47(Physics, Nuclear)The PHENIX experiment at the Relativistic Heavy Ion Collider has measured meson production and its nuclear modification in asymmetric Cu + Au heavy-ion collisions at = 200 GeV at both forward Cu-going direction (1.2 
y 2.2) backward Au-going direction (-2.2 y -1.2) rapidities. The measurements are performed via the dimuon decay channel and reported as a function of the number of participating nucleons, rapidity, and transverse momentum. In the most central events, 0% - 20% centrality, the meson yield integrated over 1 
5 GeV/
prefers a smaller value, which means a larger nuclear modification, in the Cu-going direction compared to the Au-going direction. Additionally, the nuclear-modification factor in Cu + Au collisions averaged over all centrality is measured to be similar to the previous PHENIX result in 
+ Au collisions for these rapidities.
= 7.7-200 GeVAdare, A.*; 今井 憲一; 永宮 正治; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他506名*
Physical Review C, 93(1), p.011901_1 - 011901_8, 2016/01
被引用回数：78 パーセンタイル：96.76(Physics, Nuclear)We report the measurement of cumulants (
, 
) of the net-charge distributions measured within pseudorapidity (
) in Au + Au collisions at = 7.7-200 GeV with the PHENIX experiment at the Relativistic Heavy Ion Collider. The ratios of cumulants (e.g., 
, 
) of the net-charge distributions, which can be related to volume independent susceptibility ratios, are studied as a function of centrality and energy. These quantities are important to understand the quantum-chromodynamics phase diagram and possible existence of a critical end point. The measured values are very well described by expectation from negative binomial distributions. We do not observe any nonmonotonic behavior in the ratios of the cumulants as a function of collision energy. The measured values of and can be directly compared to lattice quantum-chromodynamics calculations and thus allow extraction of both the chemical freeze-out temperature and the baryon chemical potential at each center-of-mass energy. The extracted baryon chemical potentials are in excellent agreement with a thermal-statistical analysis model.
production in 
and Au+Au collisions at = 200 GeVAdare, A.*; 今井 憲一; 谷田 聖; PHENIX Collaboration*; 他504名*
Physical Review C, 91(2), p.024913_1 - 024913_16, 2015/02
被引用回数：43 パーセンタイル：90.48(Physics, Nuclear)Measurements of bottomonium production in heavy-ion and collisions at the Relativistic Heavy Ion Collider (RHIC) are presented. The inclusive yield of the three 
states, , was measured in the PHENIX experiment via electron-positron decay pairs at midrapidity for Au+Au and collisions at 
GeV. The 
differential cross section at midrapidity was found to be 
pb in collisions. The nuclear modification factor in the 30% most central Au+Au collisions indicates a suppression of the total state yield relative to the extrapolation from collision data. The suppression is consistent with measurements made by STAR at RHIC and at higher energies by the CMS experiment at the Large Hadron Collider.
