研究者業績
基本情報
- 所属
- 国立研究開発法人宇宙航空研究開発機構 宇宙科学研究所 宇宙航空プロジェクト研究員
- 学位
- 博士(2022年3月 神戸大学)修士(2019年3月 大阪大学)学士(2017年3月 神戸大学)
- ORCID ID
https://orcid.org/0000-0002-3723-7250- J-GLOBAL ID
- 201901000915830639
- researchmap会員ID
- B000367539
経歴
2-
2022年4月 - 現在
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2019年4月 - 2022年3月
学歴
3-
2019年4月 - 2022年3月
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2017年4月 - 2019年3月
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2013年4月 - 2017年3月
委員歴
1-
2019年4月 - 2021年3月
論文
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Progress of Theoretical and Experimental Physics 2024(3) 2024年2月15日 査読有りAbstract Uncovering neutrinoless double beta decay (0ν2β) is crucial for confirming neutrinos’ Majorana characteristics. The decay rate of 0νββ is theoretically uncertain, influenced by nuclear matrix elements that vary across nuclides. To reduce this uncertainty, precise measurement of the half-life of neutrino-emitting double beta decay (2ν2β) in different nuclides is essential. We have launched the PIKACHU (Pure Inorganic scintillator experiment in KAmioka for CHallenging Underground sciences) project to fabricate high-purity Ce-doped Gd3Ga3Al2O12 (GAGG) single crystals and use them to study the double beta decay of 160Gd. Predictions from two theoretical models on nuclear matrix element calculations for 2ν2β in 160Gd show a significant discrepancy in estimated half-lives, differing by approximately an order of magnitude. If the lower half-life estimation holds true, detecting 2ν2β in 160Gd could be achievable with a sensitivity enhancement slightly more than an order of magnitude compared to prior investigations using Ce-doped Gd2SiO5 (GSO) crystal. We have successfully developed GAGG crystals with purity levels surpassing previous standards through refined purification and selection of raw materials. Our experiments with these crystals indicate the feasibility of reaching sensitivities exceeding those of earlier studies. This paper discusses the ongoing development and scintillator performance evaluation of high-purity GAGG crystals, along with the anticipated future prospects of the PIKACHU experiment.
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Physical Review Letters 131(4) 2023年7月28日 査読有り
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Physical Review D 108(1) 2023年7月26日 査読有り
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Journal of Instrumentation 18(07) P07054-P07054 2023年7月1日 査読有りAbstract The XENONnT detector uses the latest and largest liquid xenon-based time projection chamber (TPC) operated by the XENON Collaboration, aimed at detecting Weakly Interacting Massive Particles and conducting other rare event searches.The XENONnT data acquisition (DAQ) system constitutes an upgraded and expanded version of the XENON1T DAQ system.For its operation, it relies predominantly on commercially available hardware accompanied by open-source and custom-developed software.The three constituent subsystems of the XENONnT detector, the TPC (main detector), muon veto, and the newly introduced neutron veto, are integrated into a single DAQ, and can be operated both independently and as a unified system.In total, the DAQ digitizes the signals of 698 photomultiplier tubes (PMTs), of which 253 from the top PMT array of the TPC are digitized twice, at ×10 and ×0.5 gain.The DAQ for the most part is a triggerless system, reading out and storing every signal that exceeds the digitization thresholds.Custom-developed software is used to process the acquired data, making it available within ∼30 s for live data quality monitoring and online analyses.The entire system with all the three subsystems was successfully commissioned and has been operating continuously, comfortably withstanding readout rates that exceed ∼500 MB/s during calibration.Livetime during normal operation exceeds 99% and is ∼90% during most high-rate calibrations.The combined DAQ system has collected more than 2 PB of both calibration and science data during the commissioning of XENONnT and the first science run.
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Physical Review Letters 130(26) 2023年6月30日 査読有り
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The European Physical Journal C 83(6) 2023年6月27日 査読有りAbstract A low-energy electronic recoil calibration of XENON1T, a dual-phase xenon time projection chamber, with an internal $${}^{37}$$Ar source was performed. This calibration source features a 35-day half-life and provides two mono-energetic lines at 2.82 keV and 0.27 keV. The photon yield and electron yield at 2.82 keV are measured to be ($$32.3\,\pm \,0.3$$) photons/keV and ($$40.6\,\pm \,0.5$$) electrons/keV, respectively, in agreement with other measurements and with NEST predictions. The electron yield at 0.27 keV is also measured and it is ($$68.0^{+6.3}_{-3.7}$$) electrons/keV. The $${}^{37}$$Ar calibration confirms that the detector is well-understood in the energy region close to the detection threshold, with the 2.82 keV line reconstructed at ($$2.83\,\pm \,0.02$$) keV, which further validates the model used to interpret the low-energy electronic recoil excess previously reported by XENON1T. The ability to efficiently remove argon with cryogenic distillation after the calibration proves that $${}^{37}$$Ar can be considered as a regular calibration source for multi-tonne xenon detectors.
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Journal of Physics G: Nuclear and Particle Physics 50(1) 013001-013001 2023年1月1日 査読有りAbstract The nature of dark matter and properties of neutrinos are among the most pressing issues in contemporary particle physics. The dual-phase xenon time-projection chamber is the leading technology to cover the available parameter space for weakly interacting massive particles, while featuring extensive sensitivity to many alternative dark matter candidates. These detectors can also study neutrinos through neutrinoless double-beta decay and through a variety of astrophysical sources. A next-generation xenon-based detector will therefore be a true multi-purpose observatory to significantly advance particle physics, nuclear physics, astrophysics, solar physics, and cosmology. This review article presents the science cases for such a detector.
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The European Physical Journal C 82(11) 2022年11月3日 査読有りAbstract The XENON collaboration has published stringent limits on specific dark matter – nucleon recoil spectra from dark matter recoiling on the liquid xenon detector target. In this paper, we present an approximate likelihood for the XENON1T 1 t-year nuclear recoil search applicable to any nuclear recoil spectrum. Alongside this paper, we publish data and code to compute upper limits using the method we present. The approximate likelihood is constructed in bins of reconstructed energy, profiled along the signal expectation in each bin. This approach can be used to compute an approximate likelihood and therefore most statistical results for any nuclear recoil spectrum. Computing approximate results with this method is approximately three orders of magnitude faster than the likelihood used in the original publications of XENON1T, where limits were set for specific families of recoil spectra. Using this same method, we include toy Monte Carlo simulation-derived binwise likelihoods for the upcoming XENONnT experiment that can similarly be used to assess the sensitivity to arbitrary nuclear recoil signatures in its eventual 20 t-year exposure.
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Physical Review Letters 129(16) 2022年10月13日 査読有り
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Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 1045 167626-167626 2022年10月 査読有り
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Physical Review C 106(2) 2022年8月26日 査読有り
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The European Physical Journal C 82(7) 2022年7月8日 査読有りAbstract The selection of low-radioactive construction materials is of the utmost importance for rare-event searches and thus critical to the XENONnT experiment. Results of an extensive radioassay program are reported, in which material samples have been screened with gamma-ray spectroscopy, mass spectrometry, and $$^{222}$$Rn emanation measurements. Furthermore, the cleanliness procedures applied to remove or mitigate surface contamination of detector materials are described. Screening results, used as inputs for a XENONnT Monte Carlo simulation, predict a reduction of materials background ($$\sim $$17%) with respect to its predecessor XENON1T. Through radon emanation measurements, the expected $$^{222}$$Rn activity concentration in XENONnT is determined to be 4.2 ($$^{+0.5}_{-0.7}$$) $$\upmu $$Bq/kg, a factor three lower with respect to XENON1T. This radon concentration will be further suppressed by means of the novel radon distillation system.
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Physical Review D 106(2) 2022年7月5日 査読有り
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Progress of Theoretical and Experimental Physics 2022年4月29日 査読有りAbstract A novel online distillation technique was developed for the XENON1T dark matter experiment to reduce intrinsic background components more volatile than xenon, such as krypton or argon, while the detector was operating. The method is based on a continuous purification of the gaseous volume of the detector system using the XENON1T cryogenic distillation column. A krypton-in-xenon concentration of (360±60)ppq was achieved. It is the lowest concentration measured in the fiducial volume of an operating dark matter detector to date. A model was developed and fit to the data to describe the krypton evolution in the liquid and gas volumes of the detector system for several operation modes over the time span of 550 days, including the commissioning and science runs of XENON1T. The online distillation was also successfully applied to remove 37Ar after its injection for a low energy calibration in XENON1T. This makes the usage of 37Ar as a regular calibration source possible in the future. The online distillation can be applied to next-generation LXe TPC experiments to remove krypton prior to, or during, any science run. The model developed here allows further optimization of the distillation strategy for future large scale detectors.
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Journal of Instrumentation 16(12) P12033-P12033 2021年12月1日 査読有り筆頭著者責任著者Abstract Scintillation detector is widely used for the particle detection in the field of particle physics. Particle detectors containing fluorine-19 (19F) are known to have advantages for Weakly Interacting Massive Particles (WIMPs) dark matter search, especially for spin-dependent interactions with WIMPs due to its spin structure. In this study, the scintillation properties of carbontetrafluoride (CF4) gas at low temperature were evaluated because its temperature dependence of light yield has not been measured. We evaluated the light yield by cooling the gas from room temperature (300 K) to 263 K. As a result, the light yield of CF4 was found to increase by (41.0 ± 4.0stat. ± 6.6syst.)% and the energy resolution was also found to improve at low temperature.
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Physical Review D 103(9) 2021年5月26日 査読有りWe developed a CANDLES-III system to study the neutrinoless double beta (0νββ) decay of Ca48. The proposed system employs 96 CaF2 scintillation crystals (305 kg) with natural Ca (Canat) isotope which corresponds 350 g of Ca48. External backgrounds were rejected using a 4π active shield of a liquid scintillator surrounding the CaF2 crystals. The internal backgrounds caused by the radioactive impurities within the CaF2 crystals can be reduced effectively through analysis of the signal pulse shape. We analyzed the data obtained in the Kamioka underground for a live-time of 130.4 days to evaluate the feasibility of the low background measurement with the CANDLES-III detector. Using Monte Carlo simulations, we estimated the background rate from the radioactive impurities in the CaF2 crystals and the rate of high energy γ-rays caused by the (n,γ) reactions induced by environmental neutrons. The expected background rate was in a good agreement with the measured rate, i.e., approximately 10-3 events/keV/yr/(kg of Canat), in the 0νββ window. In conclusion, the background candidates were estimated properly by comparing the measured energy spectrum with the background simulations. With this measurement method, we performed the first search for 0νββ decay in a low background condition using a detector on the scale of hundreds of kg of nonenriched Ca. Deploying scintillators enriched in Ca48 will increase the sensitivity strongly. Ca48 has a high potential for use in 0νββ decay search, and is expected to be useful for the development of a next-generation detector for highly sensitive measurements.
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Physical Review D 103(6) 2021年3月19日 査読有りWe report the results of a search for the inelastic scattering of weakly interacting massive particles (WIMPs) in the XENON1T dark matter experiment. Scattering off Xe129 is the most sensitive probe of inelastic WIMP interactions, with a signature of a 39.6 keV deexcitation photon detected simultaneously with the nuclear recoil. Using an exposure of 0.83 tonne-years, we find no evidence of inelastic WIMP scattering with a significance of more than 2σ. A profile-likelihood ratio analysis is used to set upper limits on the cross section of WIMP-nucleus interactions. We exclude new parameter space for WIMPs heavier than 100 GeV/c2, with the strongest upper limit of 3.3×10-39 cm2 for 130 GeV/c2 WIMPs at 90% confidence level.
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Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 986 164727-164727 2021年1月 査読有り
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Journal of Physics: Conference Series 1643(1) 2020年12月23日 査読有りWe have studied the neutrino-less double beta decay(0νββ) of 48Ca with the CANDLES III system, which consists of CaF2(pure) scintillators. Rejection analyses for background events from radioactive contaminations in the CaF2(pure) scintillators were effective to reduce backgrounds in Qββ -value region. As the results, no events were observed in the region for the data of 131 days 86 kg. It gave a lower limit 6.2 1022 year (90 % C.L.) for the half-life of 0νββ of 48Ca. For higher sensitive measurement of 48Ca 0νββ, we have developed new techniques for 48Ca enrichment and CaF2 scintillating bolometer. In this paper, we will also show current status of these techniques.
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Journal of Cosmology and Astroparticle Physics 2020(11) 031-031 2020年11月16日 査読有りXENONnT is a dark matter direct detection experiment, utilizing 5.9 t of instrumented liquid xenon, located at the INFN Laboratori Nazionali del Gran Sasso. In this work, we predict the experimental background and project the sensitivity of XENONnT to the detection of weakly interacting massive particles (WIMPs). The expected average differential background rate in the energy region of interest, corresponding to (1, 13) keV and (4, 50) keV for electronic and nuclear recoils, amounts to 12.3 ± 0.6 (keV t y)-1 and (2.2± 0.5)× 10-3 (keV t y)-1, respectively, in a 4 t fiducial mass. We compute unified confidence intervals using the profile construction method, in order to ensure proper coverage. With the exposure goal of 20 t y, the expected sensitivity to spin-independent WIMP-nucleon interactions reaches a cross-section of 1.4×10-48 cm2 for a 50 GeV/c2 mass WIMP at 90% confidence level, more than one order of magnitude beyond the current best limit, set by XENON1T . In addition, we show that for a 50 GeV/c2 WIMP with cross-sections above 2.6×10-48 cm2 (5.0×10-48 cm2) the median XENONnT discovery significance exceeds 3σ (5σ). The expected sensitivity to the spin-dependent WIMP coupling to neutrons (protons) reaches 2.2×10-43 cm2 (6.0×10-42 cm2).
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Physical Review D 102(7) 2020年6月17日 査読有りWe report results from searches for new physics with low-energy electronic recoil data recorded with the XENON1T detector. With an exposure of 0.65 t-y and an unprecedentedly low background rate of $76\pm2$ events/(t y keV) between 1 and 30 keV, the data enables sensitive searches for solar axions, an enhanced neutrino magnetic moment, and bosonic dark matter. An excess over known backgrounds is observed at low energies and most prominent between 2 and 3 keV. The solar axion model has a 3.4$\sigma$ significance, and a 3D 90% confidence surface is reported for axion couplings to electrons, photons, and nucleons. This surface is inscribed in the cuboid defined by $g_{ae}<3.8 \times 10^{-12}$, $g_{ae}g_{an}^{eff}<4.8\times 10^{-18}$, and $g_{ae}g_{a\gamma}<7.7\times10^{-22} GeV^{-1}$, and excludes either $g_{ae}=0$ or $g_{ae}g_{a\gamma}=g_{ae}g_{an}^{eff}=0$. The neutrino magnetic moment signal is similarly favored over background at 3.2$\sigma$ and a confidence interval of $\mu_{\nu} \in (1.4,2.9)\times10^{-11}\mu_B$ (90% C.L.) is reported. Both results are in strong tension with stellar constraints. The excess can also be explained by $\beta$ decays of tritium at 3.2$\sigma$ with a trace amount that can neither be confirmed nor excluded with current knowledge of its production and reduction mechanisms. The significances of the solar axion and neutrino magnetic moment hypotheses are reduced to 2.0$\sigma$ and 0.9$\sigma$, respectively, if an unconstrained tritium component is included in the fitting. With respect to bosonic dark matter, the excess favors a monoenergetic peak at ($2.3\pm0.2$) keV (68% C.L.) with a 3.0$\sigma$ global (4.0$\sigma$ local) significance. We also consider the possibility that $^{37}$Ar may be present in the detector and yield a 2.82 keV peak. Contrary to tritium, the $^{37}$Ar concentration can be tightly constrained and is found to be negligible.
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Journal of Physics: Conference Series 1468(1) 2020年3月20日 査読有りCANDLES(CAlcium uoride for the study of Neutrinos and Dark matters by Low Energy Spectrometer) is the experiment to search for the neutrino-less double beta decay(0vβ β) of 48Ca with CaF2 scintillator. 48Ca has the highest Qβ β-value (4.3 MeV) among all isotope candidates for 0vβ β. It enables us to measure signals with very low background condition. After rejection analysis with 131 days x 86 kg data for background events from radioactive contaminations in the CaF2 scintillators, no events are observed in the Qβ β-value region. As a result, the 0vβ β half-life of 48Ca is greater than 6.2 x 1022 yr (90% confidence level). For further high sensitive measurement of 48Ca 0vβ β search, we have been developing the 48Ca enrichment and CaF2 scintillating bolometer techniques. In this paper, the latest result for CANDLES and the status of scintillating bolometer development are described.
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1468 2020年 査読有り筆頭著者最終著者責任著者
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Radiation detectors and their uses : proceedings of the 33rd Workshop on Radiation Detectors and Their Uses 42-50 2019年12月 査読有り
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2019 JINST 14 P06037 14(06) P06037-P06037 2019年6月28日 査読有り筆頭著者責任著者(Gd,La)$_2$Si$_2$O$_7$:Ce (La-GPS:Ce) is a new scintillator material with<br /> high light output, high energy resolution, and fast decay time. Moreover, the<br /> scintillator has a good light output even at high temperature (up to<br /> 150$^\circ$C) and is non-hygroscopic in nature; thus, it is especially suitable<br /> for underground resource exploration. Particle identification greatly expands<br /> the possible applications of scintillator. For resource exploration, the<br /> particle identification should be completed in a single pulse only. The<br /> pulse-shape discrimination of the scintillator was confirmed. We compared two<br /> methods; a double gate method and a digital filter method. Using digital filter<br /> method (shape indicator), F-measure to evaluate a separation between $\alpha$<br /> and $\gamma$ particles was obtained to be 0.92 at 0.66 MeVee.
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Progress of Theoretical and Experimental Physics 2018(12) 2018年12月1日 査読有り筆頭著者責任著者Abstract Ambient neutrons are one of the most serious backgrounds for underground experiments searching for rare events. The ambient neutron flux in an underground laboratory at the Kamioka Observatory was measured using a $\mathrm{^3He}$ proportional counter with various moderator setups. Since the detector response largely depends on the spectral shape, the energy spectra of the neutrons transported from the rock to the laboratory were estimated by Monte Carlo simulations. The ratio of the thermal neutron flux to the total neutron flux was found to depend on the thermalizing efficiency of the rock. Therefore, the ratio of the count rate without a moderator to that with a moderator was used to determine this parameter. Consequently, the most likely neutron spectrum predicted by the simulations for the parameters determined by the experimental results was obtained. The result suggests an interesting spectral shape, which has not been indicated in previous studies. The total ambient neutron flux is $(23.5 \pm 0.7 \ \mathrm{_{stat. } } ^{+1.9}_{-2.1} \ \mathrm{_{sys. } }) \times 10^{-6}$ cm$^{-2}$ s$^{-1}$. This result, especially the energy spectrum information, could be a new and important input for estimating the background in current and future experiments in the underground laboratory at the Kamioka Observatory.
MISC
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1468 2019年11月3日Ambient neutrons are one of the most serious backgrounds for underground<br /> experiments in search of rare events. The ambient neutron flux in an<br /> underground laboratory of Kamioka Observatory was measured using a<br /> $\mathrm{^3He}$ proportional counter with various moderator setups. Since the<br /> detector response largely depends on the spectral shape, the energy spectra of<br /> the neutrons transported from the rock to the laboratory were estimated by<br /> Monte-Carlo simulations. The ratio of the thermal neutron flux to the total<br /> neutron flux was found to depend on the thermalizing efficiency of the rock.<br /> Thus, the ratio of the count rate without a moderator to that with a moderator<br /> was used to determine this parameter. Consequently, the most-likely neutron<br /> spectrum predicted by the simulations for the parameters determined by the<br /> experimental results was obtained. The result suggests an interesting spectral<br /> shape, which has not been indicated in previous studies. The total ambient<br /> neutron flux is $(23.5 \pm 0.7 \ \mathrm{_{stat. } } ^{+1.9}_{-2.1} \<br /> \mathrm{_{sys. } }) \times 10^{-6}$ cm$^{-2}$ s$^{-1}$. In this paper, we explain<br /> our method of the result and discuss our future plan.
主要な講演・口頭発表等
31担当経験のある科目(授業)
6所属学協会
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日本学術振興会 科学研究費助成事業 2024年4月 - 2026年3月
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日本学術振興会 科学研究費助成事業 2022年8月 - 2024年3月
