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Transient beam loading effects on energy loss during beam abort in high-current storage ring
Authors:
Shuhei Obara,
Yuji Hosaka,
Ryota Saida,
Akane Agui,
Takao Asaka,
Koichi Kan,
Choji Saji,
Kota Ueshima,
Nobuyuki Nishimori
Abstract:
Beam abort by shutting off the rf cavities is a widely used machine-protection scheme in modern diffraction-limited synchrotron light source storage rings. In this process, the stored beam loses energy turn by turn until it is intercepted by a dedicated absorber. A key parameter in this process is the number of turns after the rf shutdown until the subsequent beam loss, especially for the beam-siz…
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Beam abort by shutting off the rf cavities is a widely used machine-protection scheme in modern diffraction-limited synchrotron light source storage rings. In this process, the stored beam loses energy turn by turn until it is intercepted by a dedicated absorber. A key parameter in this process is the number of turns after the rf shutdown until the subsequent beam loss, especially for the beam-size blow-up abort scheme. Despite its importance for designing an abort protection system, this quantity has not been characterized at high stored currents. We report measurements of abort turns over a broad current range from 3 to 400 mA in the 3-GeV NanoTerasu storage ring. The results show a clear current dependence: the beam is lost significantly faster at higher stored currents, with the number of turns until beam loss reduced from 435 at 3 mA to 187 at 400 mA. Our results indicate that transient beam loading induced by the aborting beam in empty rf cavities is the primary mechanism responsible for the enhanced energy loss. The number-of-turns behavior is not simply proportional to the beam loading at high current but saturates. Time-resolved cavity pickup signals, together with tracking simulations and analytical modeling, quantitatively reproduce the observed trend. Our experimental results and theoretical modeling demonstrate that transient beam loading significantly influences abort dynamics in high-current fourth-generation storage rings, emphasizing the need to incorporate this effect into machine-protection system design. Our approximate extension of the steady-state cavity-beam response to beam-abort transients reproduces experimental results well, indicating that the number of turns during a beam abort can be predicted purely numerically.
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Submitted 12 August, 2026;
originally announced August 2026.
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In-situ high voltage generation with Cockcroft-Walton multiplier for xenon gas time projection chamber
Authors:
Shinichi Akiyama,
Junya Hikida,
Masashi Yoshida,
Kazuhiro Nakamura,
Sei Ban,
Masanori Hirose,
Atsuko K. Ichikawa,
Yoshihisa Iwashita,
Tatsuya Kikawa,
Yasuhiro Nakajima,
Kiseki D. Nakamura,
Tsuyoshi Nakaya,
Shuhei Obara,
Ken Sakashita,
Hiroyuki Sekiya,
Bungo Sugashima,
Soki Urano,
Sota Hatsumi,
Sota Kobayashi,
Hayato Sasaki
Abstract:
We have newly developed a Cockcroft-Walton (CW) multiplier that can be used in a gas time projection chamber (TPC). A TPC requires a high voltage to form an electric field that drifts ionization electrons. Supplying the high voltage from outside the pressure vessel requires a dedicated high-voltage feedthrough. An alternative approach is to generate the high voltage inside the pressure vessel with…
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We have newly developed a Cockcroft-Walton (CW) multiplier that can be used in a gas time projection chamber (TPC). A TPC requires a high voltage to form an electric field that drifts ionization electrons. Supplying the high voltage from outside the pressure vessel requires a dedicated high-voltage feedthrough. An alternative approach is to generate the high voltage inside the pressure vessel with a relatively low voltage introduced from outside. A CW multiplier can convert a low AC voltage input to a high DC voltage output, making it suitable for this purpose.
We have integrated a CW multiplier into the AXEL (A Xenon ElectroLuminescence detector), a high pressure xenon gas TPC to search for neutrinoless double beta decay of $^{136}$Xe. It uses silicon photomultipliers to detect the ionization electrons through elecrtoluminescence, making it strong against electronic noise. Operation of the CW multiplier was successfully demonstrated; the TPC was operated for 40 days at 6.8 bar, and an energy resolution as high as (0.67 $\pm$ 0.08) % (FWHM) at 2615 keV was obtained.
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Submitted 7 May, 2025; v1 submitted 14 January, 2025;
originally announced January 2025.
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Commissioning of a compact multibend achromat lattice: A new 3 GeV synchrotron radiation facility
Authors:
Shuhei Obara,
Kota Ueshima,
Takao Asaka,
Yuji Hosaka,
Koichi Kan,
Nobuyuki Nishimori,
Toshitaka Aoki,
Hiroyuki Asano,
Koichi Haga,
Yuto Iba,
Akira Ihara,
Katsumasa Ito,
Taiki Iwashita,
Masaya Kadowaki,
Rento Kanahama,
Hajime Kobayashi,
Hideki Kobayashi,
Hideo Nishihara,
Masaaki Nishikawa,
Haruhiko Oikawa,
Ryota Saida,
Keisuke Sakuraba,
Kento Sugimoto,
Masahiro Suzuki,
Kouki Takahashi
, et al. (57 additional authors not shown)
Abstract:
NanoTerasu, a new 3 GeV synchrotron light source in Japan, began user operation in April 2024. It provides high-brilliance soft to tender X-rays and covers a wide spectral range from ultraviolet to tender X-rays. Its compact storage ring with a circumference of 349 m is based on a four-bend achromat lattice to provide two straight sections in each cell for insertion devices with a natural horizont…
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NanoTerasu, a new 3 GeV synchrotron light source in Japan, began user operation in April 2024. It provides high-brilliance soft to tender X-rays and covers a wide spectral range from ultraviolet to tender X-rays. Its compact storage ring with a circumference of 349 m is based on a four-bend achromat lattice to provide two straight sections in each cell for insertion devices with a natural horizontal emittance of 1.14 nm rad, which is small enough for soft X-rays users. The NanoTerasu accelerator incorporates several innovative technologies, including a full-energy injector C-band linear accelerator with a length of 110 m, an in-vacuum off-axis injection system, a four-bend achromat with B-Q combined bending magnets, and a TM020 mode accelerating cavity with built-in higher-order-mode dampers in the storage ring. This paper presents the accelerator machine commissioning over a half-year period and our model-consistent ring optics correction. The first user operation with a stored beam current of 160 mA is also reported. We summarize the storage ring parameters obtained from the commissioning. This is helpful for estimating the effective optical properties of synchrotron radiation at NanoTerasu.
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Submitted 11 July, 2024;
originally announced July 2024.
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Search for Charged Excited States of Dark Matter with KamLAND-Zen
Authors:
KamLAND-Zen collaboration,
:,
S. Abe,
M. Eizuka,
S. Futagi,
A. Gando,
Y. Gando,
S. Goto,
T. Hachiya,
K. Hata,
K. Hosokawa,
K. Ichimura,
S. Ieki,
H. Ikeda,
K. Inoue,
K. Ishidoshiro,
Y. Kamei,
N. Kawada,
Y. Kishimoto,
M. Koga,
M. Kurasawa,
T. Mitsui,
H. Miyake,
D. Morita,
T. Nakahata
, et al. (44 additional authors not shown)
Abstract:
Particle dark matter could belong to a multiplet that includes an electrically charged state. WIMP dark matter ($χ^{0}$) accompanied by a negatively charged excited state ($χ^{-}$) with a small mass difference (e.g. $<$ 20 MeV) can form a bound-state with a nucleus such as xenon. This bound-state formation is rare and the released energy is $\mathcal{O}(1-10$) MeV depending on the nucleus, making…
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Particle dark matter could belong to a multiplet that includes an electrically charged state. WIMP dark matter ($χ^{0}$) accompanied by a negatively charged excited state ($χ^{-}$) with a small mass difference (e.g. $<$ 20 MeV) can form a bound-state with a nucleus such as xenon. This bound-state formation is rare and the released energy is $\mathcal{O}(1-10$) MeV depending on the nucleus, making large liquid scintillator detectors suitable for detection. We searched for bound-state formation events with xenon in two experimental phases of the KamLAND-Zen experiment, a xenon-doped liquid scintillator detector. No statistically significant events were observed. For a benchmark parameter set of WIMP mass $m_{χ^{0}} = 1$ TeV and mass difference $Δm = 17$ MeV, we set the most stringent upper limits on the recombination cross section times velocity $\langleσv\rangle$ and the decay-width of $χ^{-}$ to $9.2 \times 10^{-30}$ ${\rm cm^3/s}$ and $8.7 \times 10^{-14}$ GeV, respectively at 90% confidence level.
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Submitted 3 July, 2024; v1 submitted 16 November, 2023;
originally announced November 2023.
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High-pressure xenon gas time projection chamber with scalable design and its performance at around the Q value of $^{136}$Xe double-beta decay
Authors:
Masashi Yoshida,
Kazuhiro Nakamura,
Shinichi Akiyama,
Sei Ban,
Junya Hikida,
Masanori Hirose,
Atsuko K. Ichikawa,
Yoshihisa Iwashita,
Yukimasa Kashino,
Tatsuya Kikawa,
Akihiro Minamino,
Kentaro Miuchi,
Yasuhiro Nakajima,
Kiseki D. Nakamura,
Tsuyoshi Nakaya,
Shuhei Obara,
Ken Sakashita,
Hiroyuki Sekiya,
Hibiki Shinagawa,
Bungo Sugashima,
Soki Urano
Abstract:
We have been developing a high-pressure xenon gas time projection chamber (TPC) to search for neutrinoless double beta ($0νββ$) decay of $^{136}$Xe. The unique feature of this TPC is in the detection part of ionization electrons, called ELCC. ELCC is composed of multiple units, and one unit covers 48.5 $\mathrm{cm}^2$. A 180 L size prototype detector with 12 units, 672 channels, of ELCC was constr…
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We have been developing a high-pressure xenon gas time projection chamber (TPC) to search for neutrinoless double beta ($0νββ$) decay of $^{136}$Xe. The unique feature of this TPC is in the detection part of ionization electrons, called ELCC. ELCC is composed of multiple units, and one unit covers 48.5 $\mathrm{cm}^2$. A 180 L size prototype detector with 12 units, 672 channels, of ELCC was constructed and operated with 7.6 bar natural xenon gas to evaluate the performance of the detector at around the Q value of $^{136}$Xe $0νββ$. The obtained FWHM energy resolution is (0.73 $\pm$ 0.11) % at 1836 keV. This corresponds to (0.60 $\pm$ 0.03) % to (0.70 $\pm$ 0.21) % of energy resolution at the Q value of $^{136}Xe$ $0νββ$. This result shows the scalability of the AXEL detector with ELCC while maintaining high energy resolution. Factors determining the energy resolution were quantitatively evaluated and the result indicates further improvement is feasible. Reconstructed track images show distinctive structures at the endpoint of electron tracks, which will be an important feature to distinguish $0νββ$ signals from gamma-ray backgrounds.
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Submitted 11 December, 2023; v1 submitted 30 October, 2023;
originally announced October 2023.
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Measurement of cosmic-ray muon spallation products in a xenon-loaded liquid scintillator with KamLAND
Authors:
KamLAND-Zen Collaboration,
:,
S. Abe,
S. Asami,
M. Eizuka,
S. Futagi,
A. Gando,
Y. Gando,
T. Gima,
A. Goto,
T. Hachiya,
K. Hata,
K. Hosokawa,
K. Ichimura,
S. Ieki,
H. Ikeda,
K. Inoue,
K. Ishidoshiro,
Y. Kamei,
N. Kawada,
Y. Kishimoto,
M. Koga,
M. Kurasawa,
T. Mitsui,
H. Miyake
, et al. (42 additional authors not shown)
Abstract:
Cosmic-ray muons produce various radioisotopes when passing through material. These spallation products can be backgrounds for rare event searches such as in solar neutrino, double-beta decay, and dark matter search experiments. The KamLAND-Zen experiment searches for neutrinoless double-beta decay in 745kg of xenon dissolved in liquid scintillator. The experiment includes dead-time-free electroni…
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Cosmic-ray muons produce various radioisotopes when passing through material. These spallation products can be backgrounds for rare event searches such as in solar neutrino, double-beta decay, and dark matter search experiments. The KamLAND-Zen experiment searches for neutrinoless double-beta decay in 745kg of xenon dissolved in liquid scintillator. The experiment includes dead-time-free electronics with a high efficiency for detecting muon-induced neutrons. The production yields of different radioisotopes are measured with a combination of delayed coincidence techniques, newly developed muon reconstruction and xenon spallation identification methods. The observed xenon spallation products are consistent with results from the FLUKA and Geant4 simulation codes.
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Submitted 23 January, 2023;
originally announced January 2023.
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Abundances of uranium and thorium elements in Earth estimated by geoneutrino spectroscopy
Authors:
S. Abe,
S. Asami,
M. Eizuka,
S. Futagi,
A. Gando,
Y. Gando,
T. Gima,
A. Goto,
T. Hachiya,
K. Hata,
K. Hosokawa,
K. Ichimura,
S. Ieki,
H. Ikeda,
K. Inoue,
K. Ishidoshiro,
Y. Kamei,
N. Kawada,
Y. Kishimoto,
M. Koga,
M. Kurasawa,
N. Maemura,
T. Mitsui,
H. Miyake,
T. Nakahata
, et al. (43 additional authors not shown)
Abstract:
The decay of the primordial isotopes $^{238}\mathrm{U}$, $^{235}\mathrm{U}$, $^{232}\mathrm{Th}$, and $^{40}\mathrm{K}$ have contributed to the terrestrial heat budget throughout the Earth's history. Hence the individual abundance of those isotopes are key parameters in reconstructing contemporary Earth model. The geoneutrinos produced by the radioactive decays of uranium and thorium have been obs…
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The decay of the primordial isotopes $^{238}\mathrm{U}$, $^{235}\mathrm{U}$, $^{232}\mathrm{Th}$, and $^{40}\mathrm{K}$ have contributed to the terrestrial heat budget throughout the Earth's history. Hence the individual abundance of those isotopes are key parameters in reconstructing contemporary Earth model. The geoneutrinos produced by the radioactive decays of uranium and thorium have been observed with the Kamioka Liquid-Scintillator Antineutrino Detector (KamLAND). Those measurements have been improved with more than 18-year observation time, and improvements in detector background levels mainly by an 8-year almost rector-free period now permit spectroscopy with geoneutrinos. Our results yield the first constraint on both uranium and thorium heat contributions. Herein the KamLAND result is consistent with geochemical estimations based on elemental abundances of chondritic meteorites and mantle peridotites. The High-Q model is disfavored at 99.76% C.L. and a fully radiogenic model is excluded at 5.2$σ$ assuming a homogeneous heat producing element distribution in the mantle.
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Submitted 13 August, 2022; v1 submitted 30 May, 2022;
originally announced May 2022.
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Search for the Majorana Nature of Neutrinos in the Inverted Mass Ordering Region with KamLAND-Zen
Authors:
KamLAND-Zen Collaboration,
:,
S. Abe,
S. Asami,
M. Eizuka,
S. Futagi,
A. Gando,
Y. Gando,
T. Gima,
A. Goto,
T. Hachiya,
K. Hata,
S. Hayashida,
K. Hosokawa,
K. Ichimura,
S. Ieki,
H. Ikeda,
K. Inoue,
K. Ishidoshiro,
Y. Kamei,
N. Kawada,
Y. Kishimoto,
M. Koga,
M. Kurasawa,
N. Maemura
, et al. (50 additional authors not shown)
Abstract:
The KamLAND-Zen experiment has provided stringent constraints on the neutrinoless double-beta ($0νββ$) decay half-life in $^{136}$Xe using a xenon-loaded liquid scintillator. We report an improved search using an upgraded detector with almost double the amount of xenon and an ultralow radioactivity container, corresponding to an exposure of 970 kg yr of $^{136}$Xe. These new data provide valuable…
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The KamLAND-Zen experiment has provided stringent constraints on the neutrinoless double-beta ($0νββ$) decay half-life in $^{136}$Xe using a xenon-loaded liquid scintillator. We report an improved search using an upgraded detector with almost double the amount of xenon and an ultralow radioactivity container, corresponding to an exposure of 970 kg yr of $^{136}$Xe. These new data provide valuable insight into backgrounds, especially from cosmic muon spallation of xenon, and have required the use of novel background rejection techniques. We obtain a lower limit for the $0νββ$ decay half-life of $T_{1/2}^{0ν} > 2.3 \times 10^{26}$ yr at 90% C.L., corresponding to upper limits on the effective Majorana neutrino mass of 36-156 meV using commonly adopted nuclear matrix element calculations.
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Submitted 16 February, 2023; v1 submitted 4 March, 2022;
originally announced March 2022.
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The nylon balloon for xenon loaded liquid scintillator in KamLAND-Zen 800 neutrinoless double-beta decay search experiment
Authors:
KamLAND-Zen collaboration,
:,
Y. Gando,
A. Gando,
T. Hachiya,
S. Hayashida,
K. Hosokawa,
H. Ikeda,
T. Mitsui,
T. Nakada,
S. Obara,
H. Ozaki,
J. Shirai,
K. Ueshima,
H. Watanabe,
S. Abe,
K. Hata,
A. Hayashi,
Y. Honda,
S. Ieki,
K. Inoue,
K. Ishidoshiro,
S. Ishikawa,
Y. Kamei,
K. Kamizawa
, et al. (49 additional authors not shown)
Abstract:
The KamLAND-Zen 800 experiment is searching for the neutrinoless double-beta decay of $^{136}$Xe by using $^{136}$Xe-loaded liquid scintillator. The liquid scintillator is enclosed inside a balloon made of thin, transparent, low-radioactivity film that we call Inner Balloon (IB). The IB, apart from guaranteeing the liquid containment, also allows to minimize the background from cosmogenic muon-spa…
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The KamLAND-Zen 800 experiment is searching for the neutrinoless double-beta decay of $^{136}$Xe by using $^{136}$Xe-loaded liquid scintillator. The liquid scintillator is enclosed inside a balloon made of thin, transparent, low-radioactivity film that we call Inner Balloon (IB). The IB, apart from guaranteeing the liquid containment, also allows to minimize the background from cosmogenic muon-spallation products and $^{8}$B solar neutrinos. Indeed these events could contribute to the total counts in the region of interest around the Q-value of the double-beta decay of $^{136}$Xe. In this paper, we present an overview of the IB and describe the various steps of its commissioning minimizing the radioactive contaminations, from the material selection, to the fabrication of the balloon and its installation inside the KamLAND detector. Finally, we show the impact of the IB on the KamLAND background as measured by the KamLAND detector itself.
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Submitted 4 June, 2021; v1 submitted 21 April, 2021;
originally announced April 2021.
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Design and performance of a high-pressure xenon gas TPC as a prototype for a large-scale neutrinoless double-beta decay search
Authors:
S. Ban,
M. Hirose,
A. K. Ichikawa,
Y. Iwashita,
T. Kikawa,
A. Minamino,
K. Miuchi,
T. Nakadaira,
Y. Nakajima,
K. D. Nakamura,
K. Z. Nakamura,
T. Nakaya,
S. Obara,
K. Sakashita,
H. Sekiya,
B. Sugashima,
S. Tanaka,
K. Ueshima,
M. Yoshida
Abstract:
A high-pressure xenon gas time projection chamber, with a unique cellular readout structure based on electroluminescence, has been developed for a large-scale neutrinoless double-beta decay search. In order to evaluate the detector performance and validate its design, a 180~L size prototype is being constructed and its commissioning with partial detector has been performed. The obtained energy res…
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A high-pressure xenon gas time projection chamber, with a unique cellular readout structure based on electroluminescence, has been developed for a large-scale neutrinoless double-beta decay search. In order to evaluate the detector performance and validate its design, a 180~L size prototype is being constructed and its commissioning with partial detector has been performed. The obtained energy resolution at 4.0~bar is 1.73 $\pm$ 0.07% (FWHM) at 511 keV. The energy resolution at the $^{136}$Xe neutrinoless double-beta decay Q-value is estimated to be between 0.79 and 1.52% (FWHM) by extrapolation. Reconstructed event topologies show patterns peculiar to track end-point which can be used to distinguish $0νββ$ signals from gamma-ray backgrounds.
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Submitted 19 February, 2020; v1 submitted 9 January, 2020;
originally announced January 2020.
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Front-end-Electronics for the SiPM-readout gaseous TPC for neutrinoless double beta decay search
Authors:
K. Z. Nakamura,
S. Ban,
A. K. Ichikawa,
M. Ikeno,
K. D. Nakamura,
T. Nakaya,
S. Obara,
S. Tanaka,
T. Uchida,
M. Yoshida
Abstract:
We have developed a dedicated front-end-electronics board for a high-pressure xenon gas time projection chamber for a neutrinoless double-beta decay search. The ionization signal is readout by detecting electroluminescence photons with SiPM's. The board readout the signal from 56~SiPM's through the DC-coupling and record the waveforms at 5 MS/s with a wide dynamic range up to 7,000 photons/200 ns.…
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We have developed a dedicated front-end-electronics board for a high-pressure xenon gas time projection chamber for a neutrinoless double-beta decay search. The ionization signal is readout by detecting electroluminescence photons with SiPM's. The board readout the signal from 56~SiPM's through the DC-coupling and record the waveforms at 5 MS/s with a wide dynamic range up to 7,000 photons/200 ns. The SiPM bias voltages are provided by the board and can be adjusted for each SiPM. In order to calibrate and monitor the SiPM gain, additional auxiliary ADC measures 1 photon-equivalent dark current. The obtained performance satisfies the requirement for a neutrinoless double-beta decay search.
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Submitted 6 January, 2020;
originally announced January 2020.
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Scintillation balloon for liquid scintillator base Neutrinoless double beta decay search experiments
Authors:
S. Obara,
Y. Gando,
K. Ishidoshiro
Abstract:
A liquid scintillator base experiment KamLAND-Zen has set a lower limit on neutrinoless double beta decay half-life, and upgrade project KamLAND-Zen 800 has started in 2019. Unfortunately, this project expects some backgrounds, and one of the main backgrounds is beta/gamma-ray from 214Bi in container of xenon loaded liquid scintillator (mini-balloon). In order to reject the background, we suggest…
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A liquid scintillator base experiment KamLAND-Zen has set a lower limit on neutrinoless double beta decay half-life, and upgrade project KamLAND-Zen 800 has started in 2019. Unfortunately, this project expects some backgrounds, and one of the main backgrounds is beta/gamma-ray from 214Bi in container of xenon loaded liquid scintillator (mini-balloon). In order to reject the background, we suggest using scintillation film for the future mini-balloon. If we can tag alpha-ray from 214Po by scintillation detection, we can eliminate 214Bi events by delayed coincidence analysis. Recently, it was reported that polyethylene naphthalate (PEN) can be used as a scintillator with blue photon emission. PEN has chemical compatibility for strong solvent, thus it has a possibility to use in liquid scintillator. In this presentation, we will mention the results for feasibility studies about transparency and emission spectra, light yield, radioactivity, strength of film etc.. We also show the test-sized scintillation balloon with an 800-mm diameter and discussions about how to use the scintillation balloon in KamLAND.
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Submitted 16 December, 2019;
originally announced December 2019.
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AXEL: High-pressure Xe gas TPC for BG-free $0\nu2β$ decay search
Authors:
S. Obara,
S. Ban,
M. Hirose,
A. K. Ichikawa,
T. Kikawa,
K. Z. Nakamura,
T. Nakaya,
S. Tanaka,
M. Yoshida,
Y. Iwashita,
H. Sekiya,
Y. Nakajima,
K. Ueshima,
K. Miuchi,
K. D. Nakamura,
A. Minamino,
T. Nakadaira,
K. Sakashita
Abstract:
AXEL is a high-pressure xenon gas time projection chamber for neutrinoless double-beta decay (0n2b) search. The AXEL has a unique readout system called ELCC which has a cellular structure and photosensors to detect electroluminescence light produced by ionization electrons. We demonstrated the performance of the ELCC with a small prototype detector (AXEL-HP10L). The obtained energy resolution corr…
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AXEL is a high-pressure xenon gas time projection chamber for neutrinoless double-beta decay (0n2b) search. The AXEL has a unique readout system called ELCC which has a cellular structure and photosensors to detect electroluminescence light produced by ionization electrons. We demonstrated the performance of the ELCC with a small prototype detector (AXEL-HP10L). The obtained energy resolution corresponds to 0.82 -- 1.74% (FWHM) at the 0n2b Q-value. We are constructing a new prototype (AXEL-HP180L) in order to study the energy resolution at the Q-value of 0n2b with a new design of ELCC with unit structure, newly developed electronics board, field-shaping electrodes, and Cockcroft-Walton-type high voltage power supply. For a future 1-ton scale large AXEL detector, we are developing new background-reduction techniques; topology identification with machine learning, positive-ion detection, and active-shield options.
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Submitted 30 September, 2019; v1 submitted 20 September, 2019;
originally announced September 2019.
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Scintillation Balloon for Neutrinoless Double-Beta Decay Search with Liquid Scintillator Detectors
Authors:
S. Obara,
Y. Gando,
K. Ishidoshiro
Abstract:
Environmental radioactivity is a dominant background for rare decay search experiments, and it is difficult to completely remove such an impurity from detector vessels. We propose a scintillation balloon as the active vessel of a liquid scintillator in order to identify this undesirable radioactivity. According to our feasibility studies, the scintillation balloon enables the bismuth--polonium seq…
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Environmental radioactivity is a dominant background for rare decay search experiments, and it is difficult to completely remove such an impurity from detector vessels. We propose a scintillation balloon as the active vessel of a liquid scintillator in order to identify this undesirable radioactivity. According to our feasibility studies, the scintillation balloon enables the bismuth--polonium sequential decay to be tagged with a 99.7\% efficiency, assuming a KamLAND (Kamioka Liquid scintillator AntiNeutrino Detector)-type liquid scintillator detector. This tagging of sequential decay using alpha-ray from the polonium improves the sensitivity to neutrinoless double-beta decay with rejecting beta-ray background from the bismuth.
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Submitted 3 June, 2019; v1 submitted 26 March, 2019;
originally announced March 2019.
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Search for double-beta decay of 136Xe to excited states of 136Ba with the KamLAND-Zen experiment
Authors:
KamLAND-Zen Collaboration,
:,
K. Asakura,
A. Gando,
Y. Gando,
T. Hachiya,
S. Hayashida,
H. Ikeda,
K. Inoue,
K. Ishidoshiro,
T. Ishikawa,
S. Ishio,
M. Koga,
S. Matsuda,
T. Mitsui,
D. Motoki,
K. Nakamura,
S. Obara,
M. Otani,
T. Oura,
I. Shimizu,
Y. Shirahata,
J. Shirai,
A. Suzuki,
H. Tachibana
, et al. (21 additional authors not shown)
Abstract:
A search for double-beta decays of 136Xe to excited states of 136Ba has been performed with the first phase data set of the KamLAND-Zen experiment. The 0+1, 2+1 and 2+2 transitions of 0ν\{beta}\{beta} decay were evaluated in an exposure of 89.5kg-yr of 136Xe, while the same transitions of 2ν\{beta}\{beta} decay were evaluated in an exposure of 61.8kg-yr. No excess over background was found for all…
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A search for double-beta decays of 136Xe to excited states of 136Ba has been performed with the first phase data set of the KamLAND-Zen experiment. The 0+1, 2+1 and 2+2 transitions of 0ν\{beta}\{beta} decay were evaluated in an exposure of 89.5kg-yr of 136Xe, while the same transitions of 2ν\{beta}\{beta} decay were evaluated in an exposure of 61.8kg-yr. No excess over background was found for all decay modes. The lower half-life limits of the 2+1 state transitions of 0ν\{beta}\{beta} and 2ν\{beta}\{beta} decay were improved to T(0ν, 0+ \rightarrow 2+) > 2.6\times10^25 yr and T(2ν, 0+ \rightarrow 2+) > 4.6\times10^23 yr (90% C.L.), respectively. We report on the first experimental lower half-life limits for the transitions to the 0+1 state of 136Xe for 0ν\{beta}\{beta} and 2ν\{beta}\{beta} decay. They are T (0ν, 0+ \rightarrow 0+) > 2.4\times10^25 yr and T(2ν, 0+ \rightarrow 0+) > 8.3\times10^23 yr (90% C.L.). The transitions to the 2+2 states are also evaluated for the first time to be T(0ν, 0+ \rightarrow 2+) > 2.6\times10^25 yr and T(2ν, 0+ \rightarrow 2+) > 9.0\times10^23 yr (90% C.L.). These results are compared to recent theoretical predictions.
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Submitted 8 December, 2015; v1 submitted 12 September, 2015;
originally announced September 2015.
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KamLAND Sensitivity to Neutrinos from Pre-Supernova Stars
Authors:
K. Asakura,
A. Gando,
Y. Gando,
T. Hachiya,
S. Hayashida,
H. Ikeda,
K. Inoue,
K. Ishidoshiro,
T. Ishikawa,
S. Ishio,
M. Koga,
S. Matsuda,
T. Mitsui,
D. Motoki,
K. Nakamura,
S. Obara,
T. Oura,
I. Shimizu,
Y. Shirahata,
J. Shirai,
A. Suzuki,
H. Tachibana,
K. Tamae,
K. Ueshima,
H. Watanabe
, et al. (22 additional authors not shown)
Abstract:
In the late stages of nuclear burning for massive stars ($M>8~M_{\sun}$), the production of neutrino-antineutrino pairs through various processes becomes the dominant stellar cooling mechanism. As the star evolves, the energy of these neutrinos increases and in the days preceding the supernova a significant fraction of emitted electron anti-neutrinos exceeds the energy threshold for inverse beta d…
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In the late stages of nuclear burning for massive stars ($M>8~M_{\sun}$), the production of neutrino-antineutrino pairs through various processes becomes the dominant stellar cooling mechanism. As the star evolves, the energy of these neutrinos increases and in the days preceding the supernova a significant fraction of emitted electron anti-neutrinos exceeds the energy threshold for inverse beta decay on free hydrogen. This is the golden channel for liquid scintillator detectors because the coincidence signature allows for significant reductions in background signals. We find that the kiloton-scale liquid scintillator detector KamLAND can detect these pre-supernova neutrinos from a star with a mass of $25~M_{\sun}$ at a distance less than 690~pc with 3$σ$ significance before the supernova. This limit is dependent on the neutrino mass ordering and background levels. KamLAND takes data continuously and can provide a supernova alert to the community.
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Submitted 22 January, 2016; v1 submitted 3 June, 2015;
originally announced June 2015.