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First Associated Neutrino Search for a Failed Supernova Candidate with Super-Kamiokande
Authors:
F. Nakanishi,
K. Abe,
S. Abe,
Y. Asaoka,
M. Harada,
Y. Hayato,
K. Hiraide,
K. Hosokawa,
T. H. Hung,
K. Ieki,
M. Ikeda,
J. Kameda,
Y. Kanemura,
Y. Kataoka,
S. Miki,
S. Mine,
M. Miura,
S. Moriyama,
M. Nakahata,
S. Nakayama,
Y. Noguchi,
G. Pronost,
K. Sato,
H. Sekiya,
M. Shiozawa
, et al. (221 additional authors not shown)
Abstract:
In 2024, a failed supernova candidate, M31-2014-DS1, was reported in the Andromeda galaxy (M31), located at a distance of approximately 770 kpc. In this paper, we search for neutrinos from this failed supernova using data from Super-Kamiokande (SK). Based on the estimated time of black hole formation inferred from optical and infrared observations, we define a search window for neutrino events in…
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In 2024, a failed supernova candidate, M31-2014-DS1, was reported in the Andromeda galaxy (M31), located at a distance of approximately 770 kpc. In this paper, we search for neutrinos from this failed supernova using data from Super-Kamiokande (SK). Based on the estimated time of black hole formation inferred from optical and infrared observations, we define a search window for neutrino events in the SK data. Using this window, we develop a dedicated analysis method for failed supernovae and apply it to M31-2014-DS1, by conducting a cluster search using the timing and energy information of candidate events. No significant neutrino excess is observed within the search region. Consequently, we place an upper limit on the electron antineutrino luminosity from M31-2014-DS1 and discuss its implications for various failed SN models and their neutrino emission characteristics. Despite the 18 MeV threshold adopted to suppress backgrounds, the search remains sufficiently sensitive to constrain the Shen-TM1 EOS, yielding a 90% confidence level upper limit of 1.76 \times 10^{53} erg on the electron antineutrino luminosity, slightly above the expected value of 1.35 \times 10^{53} erg.
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Submitted 5 November, 2025; v1 submitted 5 November, 2025;
originally announced November 2025.
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Search for Diffuse Supernova Neutrino Background with 956.2 days of Super-Kamiokande Gadolinium Dataset
Authors:
K. Abe,
S. Abe,
Y. Asaoka,
M. Harada,
Y. Hayato,
K. Hiraide,
K. Hosokawa,
T. H. Hung,
K. Ieki,
M. Ikeda,
J. Kameda,
Y. Kanemura,
Y. Kataoka,
S. Miki,
S. Mine,
M. Miura,
S. Moriyama,
M. Nakahata,
S. Nakayama,
Y. Noguchi,
G. Pronost,
K. Sato,
H. Sekiya,
R. Shinoda,
M. Shiozawa
, et al. (223 additional authors not shown)
Abstract:
We report the search result for the Diffuse Supernova Neutrino Background (DSNB) in neutrino energies beyond 9.3~MeV in the gadolinium-loaded Super-Kamiokande (SK) detector with $22,500\times956.2$$~\rm m^3\cdot day$ exposure. %$22.5{\rm k}\times956.2$$~\rm m^3\cdot day$ exposure. Starting in the summer of 2020, SK introduced 0.01\% gadolinium (Gd) by mass into its ultra-pure water to enhance the…
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We report the search result for the Diffuse Supernova Neutrino Background (DSNB) in neutrino energies beyond 9.3~MeV in the gadolinium-loaded Super-Kamiokande (SK) detector with $22,500\times956.2$$~\rm m^3\cdot day$ exposure. %$22.5{\rm k}\times956.2$$~\rm m^3\cdot day$ exposure. Starting in the summer of 2020, SK introduced 0.01\% gadolinium (Gd) by mass into its ultra-pure water to enhance the neutron capture signal, termed the SK-VI phase. This was followed by a 0.03\% Gd-loading in 2022, a phase referred to as SK-VII. We then conducted a DSNB search using 552.2~days of SK-VI data and 404.0~days of SK-VII data through September 2023. This analysis includes several new features, such as two new machine-learning neutron detection algorithms with Gd, an improved atmospheric background reduction technique, and two parallel statistical approaches. No significant excess over background predictions was found in a DSNB spectrum-independent analysis, and 90\% C.L. upper limits on the astrophysical electron anti-neutrino flux were set. Additionally, a spectral fitting result exhibited a $\sim1.2σ$ disagreement with a null DSNB hypothesis, comparable to a previous result from 5823~days of all SK pure water phases.
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Submitted 3 November, 2025;
originally announced November 2025.
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Combined Pre-Supernova Alert System with Kamland and Super-Kamiokande
Authors:
KamLAND,
Super-Kamiokande Collaborations,
:,
Seisho Abe,
Minori Eizuka,
Sawako Futagi,
Azusa Gando,
Yoshihito Gando,
Shun Goto,
Takahiko Hachiya,
Kazumi Hata,
Koichi Ichimura,
Sei Ieki,
Haruo Ikeda,
Kunio Inoue,
Koji Ishidoshiro,
Yuto Kamei,
Nanami Kawada,
Yasuhiro Kishimoto,
Masayuki Koga,
Maho Kurasawa,
Tadao Mitsui,
Haruhiko Miyake,
Daisuke Morita,
Takeshi Nakahata
, et al. (290 additional authors not shown)
Abstract:
Preceding a core-collapse supernova, various processes produce an increasing amount of neutrinos of all flavors characterized by mounting energies from the interior of massive stars. Among them, the electron antineutrinos are potentially detectable by terrestrial neutrino experiments such as KamLAND and Super-Kamiokande via inverse beta decay interactions. Once these pre-supernova neutrinos are ob…
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Preceding a core-collapse supernova, various processes produce an increasing amount of neutrinos of all flavors characterized by mounting energies from the interior of massive stars. Among them, the electron antineutrinos are potentially detectable by terrestrial neutrino experiments such as KamLAND and Super-Kamiokande via inverse beta decay interactions. Once these pre-supernova neutrinos are observed, an early warning of the upcoming core-collapse supernova can be provided. In light of this, KamLAND and Super-Kamiokande, both located in the Kamioka mine in Japan, have been monitoring pre-supernova neutrinos since 2015 and 2021, respectively. Recently, we performed a joint study between KamLAND and Super-Kamiokande on pre-supernova neutrino detection. A pre-supernova alert system combining the KamLAND detector and the Super-Kamiokande detector was developed and put into operation, which can provide a supernova alert to the astrophysics community. Fully leveraging the complementary properties of these two detectors, the combined alert is expected to resolve a pre-supernova neutrino signal from a 15 M$_{\odot}$ star within 510 pc of the Earth, at a significance level corresponding to a false alarm rate of no more than 1 per century. For a Betelgeuse-like model with optimistic parameters, it can provide early warnings up to 12 hours in advance.
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Submitted 1 July, 2024; v1 submitted 15 April, 2024;
originally announced April 2024.
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Development of a data overflow protection system for Super-Kamiokande to maximize data from nearby supernovae
Authors:
M. Mori,
K. Abe,
Y. Hayato,
K. Hiraide,
K. Hosokawa,
K. Ieki,
M. Ikeda,
J. Kameda,
Y. Kanemura,
R. Kaneshima,
Y. Kashiwagi,
Y. Kataoka,
S. Miki,
S. Mine,
M. Miura,
S. Moriyama,
Y. Nakano,
M. Nakahata,
S. Nakayama,
Y. Noguchi,
K. Okamoto,
K. Sato,
H. Sekiya,
H. Shiba,
K. Shimizu
, et al. (230 additional authors not shown)
Abstract:
Neutrinos from very nearby supernovae, such as Betelgeuse, are expected to generate more than ten million events over 10\,s in Super-Kamokande (SK). At such large event rates, the buffers of the SK analog-to-digital conversion board (QBEE) will overflow, causing random loss of data that is critical for understanding the dynamics of the supernova explosion mechanism. In order to solve this problem,…
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Neutrinos from very nearby supernovae, such as Betelgeuse, are expected to generate more than ten million events over 10\,s in Super-Kamokande (SK). At such large event rates, the buffers of the SK analog-to-digital conversion board (QBEE) will overflow, causing random loss of data that is critical for understanding the dynamics of the supernova explosion mechanism. In order to solve this problem, two new DAQ modules were developed to aid in the observation of very nearby supernovae. The first of these, the SN module, is designed to save only the number of hit PMTs during a supernova burst and the second, the Veto module, prescales the high rate neutrino events to prevent the QBEE from overflowing based on information from the SN module. In the event of a very nearby supernova, these modules allow SK to reconstruct the time evolution of the neutrino event rate from beginning to end using both QBEE and SN module data. This paper presents the development and testing of these modules together with an analysis of supernova-like data generated with a flashing laser diode. We demonstrate that the Veto module successfully prevents DAQ overflows for Betelgeuse-like supernovae as well as the long-term stability of the new modules. During normal running the Veto module is found to issue DAQ vetos a few times per month resulting in a total dead time less than 1\,ms, and does not influence ordinary operations. Additionally, using simulation data we find that supernovae closer than 800~pc will trigger Veto module resulting in a prescaling of the observed neutrino data.
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Submitted 13 August, 2024; v1 submitted 12 April, 2024;
originally announced April 2024.
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Measurements of the charge ratio and polarization of cosmic-ray muons with the Super-Kamiokande detector
Authors:
H. Kitagawa,
T. Tada,
K. Abe,
C. Bronner,
Y. Hayato,
K. Hiraide,
K. Hosokawa,
K. Ieki,
M. Ikeda,
J. Kameda,
Y. Kanemura,
R. Kaneshima,
Y. Kashiwagi,
Y. Kataoka,
S. Miki,
S. Mine,
M. Miura,
S. Moriyama,
Y. Nakano,
M. Nakahata,
S. Nakayama,
Y. Noguchi,
K. Okamoto,
K. Sato,
H. Sekiya
, et al. (231 additional authors not shown)
Abstract:
We present the results of the charge ratio ($R$) and polarization ($P^μ_{0}$) measurements using the decay electron events collected from 2008 September to 2022 June by the Super-Kamiokande detector. Because of its underground location and long operation, we performed high precision measurements by accumulating cosmic-ray muons. We measured the muon charge ratio to be $R=1.32 \pm 0.02$…
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We present the results of the charge ratio ($R$) and polarization ($P^μ_{0}$) measurements using the decay electron events collected from 2008 September to 2022 June by the Super-Kamiokande detector. Because of its underground location and long operation, we performed high precision measurements by accumulating cosmic-ray muons. We measured the muon charge ratio to be $R=1.32 \pm 0.02$ $(\mathrm{stat.}{+}\mathrm{syst.})$ at $E_μ\cos θ_{\mathrm{Zenith}}=0.7^{+0.3}_{-0.2}$ $\mathrm{TeV}$, where $E_μ$ is the muon energy and $θ_{\mathrm{Zenith}}$ is the zenith angle of incoming cosmic-ray muons. This result is consistent with the Honda flux model while this suggests a tension with the $πK$ model of $1.9σ$. We also measured the muon polarization at the production location to be $P^μ_{0}=0.52 \pm 0.02$ $(\mathrm{stat.}{+}\mathrm{syst.})$ at the muon momentum of $0.9^{+0.6}_{-0.1}$ $\mathrm{TeV}/c$ at the surface of the mountain; this also suggests a tension with the Honda flux model of $1.5σ$. This is the most precise measurement ever to experimentally determine the cosmic-ray muon polarization near $1~\mathrm{TeV}/c$. These measurement results are useful to improve the atmospheric neutrino simulations.
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Submitted 4 November, 2024; v1 submitted 13 March, 2024;
originally announced March 2024.
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Second gadolinium loading to Super-Kamiokande
Authors:
K. Abe,
C. Bronner,
Y. Hayato,
K. Hiraide,
K. Hosokawa,
K. Ieki,
M. Ikeda,
J. Kameda,
Y. Kanemura,
R. Kaneshima,
Y. Kashiwagi,
Y. Kataoka,
S. Miki,
S. Mine,
M. Miura,
S. Moriyama,
Y. Nakano,
M. Nakahata,
S. Nakayama,
Y. Noguchi,
K. Sato,
H. Sekiya,
H. Shiba,
K. Shimizu,
M. Shiozawa
, et al. (225 additional authors not shown)
Abstract:
The first loading of gadolinium (Gd) into Super-Kamiokande in 2020 was successful, and the neutron capture efficiency on Gd reached 50\%. To further increase the Gd neutron capture efficiency to 75\%, 26.1 tons of $\rm Gd_2(\rm SO_4)_3\cdot \rm 8H_2O$ was additionally loaded into Super-Kamiokande (SK) from May 31 to July 4, 2022. As the amount of loaded $\rm Gd_2(\rm SO_4)_3\cdot \rm 8H_2O$ was do…
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The first loading of gadolinium (Gd) into Super-Kamiokande in 2020 was successful, and the neutron capture efficiency on Gd reached 50\%. To further increase the Gd neutron capture efficiency to 75\%, 26.1 tons of $\rm Gd_2(\rm SO_4)_3\cdot \rm 8H_2O$ was additionally loaded into Super-Kamiokande (SK) from May 31 to July 4, 2022. As the amount of loaded $\rm Gd_2(\rm SO_4)_3\cdot \rm 8H_2O$ was doubled compared to the first loading, the capacity of the powder dissolving system was doubled. We also developed new batches of gadolinium sulfate with even further reduced radioactive impurities. In addition, a more efficient screening method was devised and implemented to evaluate these new batches of $\rm Gd_2(\rm SO_4)_3\cdot \rm 8H_2O$. Following the second loading, the Gd concentration in SK was measured to be $333.5\pm2.5$ ppm via an Atomic Absorption Spectrometer (AAS). From the mean neutron capture time constant of neutrons from an Am/Be calibration source, the Gd concentration was independently measured to be 332.7 $\pm$ 6.8(sys.) $\pm$ 1.1(stat.) ppm, consistent with the AAS result. Furthermore, during the loading the Gd concentration was monitored continually using the capture time constant of each spallation neutron produced by cosmic-ray muons,and the final neutron capture efficiency was shown to become 1.5 times higher than that of the first loaded phase, as expected.
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Submitted 18 June, 2024; v1 submitted 12 March, 2024;
originally announced March 2024.
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Performance of SK-Gd's Upgraded Real-time Supernova Monitoring System
Authors:
Y. Kashiwagi,
K. Abe,
C. Bronner,
Y. Hayato,
K. Hiraide,
K. Hosokawa,
K. Ieki,
M. Ikeda,
J. Kameda,
Y. Kanemura,
R. Kaneshima,
Y. Kataoka,
S. Miki,
S. Mine,
M. Miura,
S. Moriyama,
Y. Nakano,
M. Nakahata,
S. Nakayama,
Y. Noguchi,
K. Sato,
H. Sekiya,
H. Shiba,
K. Shimizu,
M. Shiozawa
, et al. (214 additional authors not shown)
Abstract:
Among multi-messenger observations of the next galactic core-collapse supernova, Super-Kamiokande (SK) plays a critical role in detecting the emitted supernova neutrinos, determining the direction to the supernova (SN), and notifying the astronomical community of these observations in advance of the optical signal. On 2022, SK has increased the gadolinium dissolved in its water target (SK-Gd) and…
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Among multi-messenger observations of the next galactic core-collapse supernova, Super-Kamiokande (SK) plays a critical role in detecting the emitted supernova neutrinos, determining the direction to the supernova (SN), and notifying the astronomical community of these observations in advance of the optical signal. On 2022, SK has increased the gadolinium dissolved in its water target (SK-Gd) and has achieved a Gd concentration of 0.033%, resulting in enhanced neutron detection capability, which in turn enables more accurate determination of the supernova direction. Accordingly, SK-Gd's real-time supernova monitoring system (Abe te al. 2016b) has been upgraded. SK_SN Notice, a warning system that works together with this monitoring system, was released on December 13, 2021, and is available through GCN Notices (Barthelmy et al. 2000). When the monitoring system detects an SN-like burst of events, SK_SN Notice will automatically distribute an alarm with the reconstructed direction to the supernova candidate within a few minutes. In this paper, we present a systematic study of SK-Gd's response to a simulated galactic SN. Assuming a supernova situated at 10 kpc, neutrino fluxes from six supernova models are used to characterize SK-Gd's pointing accuracy using the same tools as the online monitoring system. The pointing accuracy is found to vary from 3-7$^\circ$ depending on the models. However, if the supernova is closer than 10 kpc, SK_SN Notice can issue an alarm with three-degree accuracy, which will benefit follow-up observations by optical telescopes with large fields of view.
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Submitted 13 March, 2024; v1 submitted 11 March, 2024;
originally announced March 2024.
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Search for astrophysical electron antineutrinos in Super-Kamiokande with 0.01wt% gadolinium-loaded water
Authors:
M. Harada,
K. Abe,
C. Bronner,
Y. Hayato,
K. Hiraide,
K. Hosokawa,
K. Ieki,
M. Ikeda,
J. Kameda,
Y. Kanemura,
R. Kaneshima,
Y. Kashiwagi,
Y. Kataoka,
S. Miki,
S. Mine,
M. Miura,
S. Moriyama,
Y. Nakano,
M. Nakahata,
S. Nakayama,
Y. Noguchi,
K. Okamoto,
K. Sato,
H. Sekiya,
H. Shiba
, et al. (216 additional authors not shown)
Abstract:
We report the first search result for the flux of astrophysical electron antineutrinos for energies O(10) MeV in the gadolinium-loaded Super-Kamiokande (SK) detector. In June 2020, gadolinium was introduced to the ultra-pure water of the SK detector in order to detect neutrons more efficiently. In this new experimental phase, SK-Gd, we can search for electron antineutrinos via inverse beta decay w…
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We report the first search result for the flux of astrophysical electron antineutrinos for energies O(10) MeV in the gadolinium-loaded Super-Kamiokande (SK) detector. In June 2020, gadolinium was introduced to the ultra-pure water of the SK detector in order to detect neutrons more efficiently. In this new experimental phase, SK-Gd, we can search for electron antineutrinos via inverse beta decay with efficient background rejection and higher signal efficiency thanks to the high efficiency of the neutron tagging technique. In this paper, we report the result for the initial stage of SK-Gd with a $22.5\times552$ $\rm kton\cdot day$ exposure at 0.01% Gd mass concentration. No significant excess over the expected background in the observed events is found for the neutrino energies below 31.3 MeV. Thus, the flux upper limits are placed at the 90% confidence level. The limits and sensitivities are already comparable with the previous SK result with pure-water ($22.5 \times 2970 \rm kton\cdot day$) owing to the enhanced neutron tagging.
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Submitted 30 May, 2023; v1 submitted 8 May, 2023;
originally announced May 2023.
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Searching for neutrinos from solar flares across solar cycles 23 and 24 with the Super-Kamiokande detector
Authors:
K. Okamoto,
K. Abe,
Y. Hayato,
K. Hiraide,
K. Hosokawa,
K. Ieki,
M. Ikeda,
J. Kameda,
Y. Kanemura,
Y. Kaneshima,
Y. Kataoka,
Y. Kashiwagi,
S. Miki,
S. Mine,
M. Miura,
S. Moriyama,
Y. Nagao,
M. Nakahata,
Y. Nakano,
S. Nakayama,
Y. Noguchi,
K. Sato,
H. Sekiya,
K. Shimizu,
M. Shiozawa
, et al. (220 additional authors not shown)
Abstract:
Neutrinos associated with solar flares (solar-flare neutrinos) provide information on particle acceleration mechanisms during the impulsive phase of solar flares. We searched using the Super-Kamiokande detector for neutrinos from solar flares that occurred during solar cycles $23$ and $24$, including the largest solar flare (X28.0) on November 4th, 2003. In order to minimize the background rate we…
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Neutrinos associated with solar flares (solar-flare neutrinos) provide information on particle acceleration mechanisms during the impulsive phase of solar flares. We searched using the Super-Kamiokande detector for neutrinos from solar flares that occurred during solar cycles $23$ and $24$, including the largest solar flare (X28.0) on November 4th, 2003. In order to minimize the background rate we searched for neutrino interactions within narrow time windows coincident with $γ$-rays and soft X-rays recorded by satellites. In addition, we performed the first attempt to search for solar-flare neutrinos from solar flares on the invisible side of the Sun by using the emission time of coronal mass ejections (CMEs). By selecting twenty powerful solar flares above X5.0 on the visible side and eight CMEs whose emission speed exceeds $2000$ $\mathrm{km \, s^{-1}}$ on the invisible side from 1996 to 2018, we found two (six) neutrino events coincident with solar flares occurring on the visible (invisible) side of the Sun, with a typical background rate of $0.10$ ($0.62$) events per flare in the MeV-GeV energy range. No significant solar-flare neutrino signal above the estimated background rate was observed. As a result we set the following upper limit on neutrino fluence at the Earth $\mathitΦ<1.1\times10^{6}$ $\mathrm{cm^{-2}}$ at the $90\%$ confidence level for the largest solar flare. The resulting fluence limits allow us to constrain some of the theoretical models for solar-flare neutrino emission.
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Submitted 26 October, 2022; v1 submitted 24 October, 2022;
originally announced October 2022.
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Neutron Tagging following Atmospheric Neutrino Events in a Water Cherenkov Detector
Authors:
K. Abe,
Y. Haga,
Y. Hayato,
K. Hiraide,
K. Ieki,
M. Ikeda,
S. Imaizumi,
K. Iyogi,
J. Kameda,
Y. Kanemura,
Y. Kataoka,
Y. Kato,
Y. Kishimoto,
S. Miki,
S. Mine,
M. Miura,
T. Mochizuki,
S. Moriyama,
Y. Nagao,
M. Nakahata,
T. Nakajima,
Y. Nakano,
S. Nakayama,
T. Okada,
K. Okamoto
, et al. (281 additional authors not shown)
Abstract:
We present the development of neutron-tagging techniques in Super-Kamiokande IV using a neural network analysis. The detection efficiency of neutron capture on hydrogen is estimated to be 26%, with a mis-tag rate of 0.016 per neutrino event. The uncertainty of the tagging efficiency is estimated to be 9.0%. Measurement of the tagging efficiency with data from an Americium-Beryllium calibration agr…
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We present the development of neutron-tagging techniques in Super-Kamiokande IV using a neural network analysis. The detection efficiency of neutron capture on hydrogen is estimated to be 26%, with a mis-tag rate of 0.016 per neutrino event. The uncertainty of the tagging efficiency is estimated to be 9.0%. Measurement of the tagging efficiency with data from an Americium-Beryllium calibration agrees with this value within 10%. The tagging procedure was performed on 3,244.4 days of SK-IV atmospheric neutrino data, identifying 18,091 neutrons in 26,473 neutrino events. The fitted neutron capture lifetime was measured as 218 \pm 9 μs.
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Submitted 20 September, 2022; v1 submitted 18 September, 2022;
originally announced September 2022.
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Search for supernova bursts in Super-Kamiokande IV
Authors:
The Super-Kamiokande collaboration,
:,
M. Mori,
K. Abe,
Y. Hayato,
K. Hiraide,
K. Ieki,
M. Ikeda,
S. Imaizumi,
J. Kameda,
Y. Kanemura,
R. Kaneshima,
Y. Kashiwagi,
Y. Kataoka,
S. Miki,
S. Mine,
M. Miura,
S. Moriyama,
Y. Nagao,
M. Nakahata,
Y. Nakano,
S. Nakayama,
Y. Noguchi,
T. Okada,
K. Okamoto
, et al. (223 additional authors not shown)
Abstract:
Super-Kamiokande has been searching for neutrino bursts characteristic of core-collapse supernovae continuously, in real time, since the start of operations in 1996. The present work focuses on detecting more distant supernovae whose event rate may be too small to trigger in real time, but may be identified using an offline approach. The analysis of data collected from 2008 to 2018 found no eviden…
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Super-Kamiokande has been searching for neutrino bursts characteristic of core-collapse supernovae continuously, in real time, since the start of operations in 1996. The present work focuses on detecting more distant supernovae whose event rate may be too small to trigger in real time, but may be identified using an offline approach. The analysis of data collected from 2008 to 2018 found no evidence of distant supernovae bursts. This establishes an upper limit of 0.29 year$^{-1}$ on the rate of core-collapse supernovae out to 100 kpc at 90% C.L.. For supernovae that fail to explode and collapse directly to black holes the limit reaches to 300 kpc.
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Submitted 2 June, 2022;
originally announced June 2022.
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Pre-Supernova Alert System for Super-Kamiokande
Authors:
Super-Kamiokande Collaboration,
:,
L. N. Machado,
K. Abe,
Y. Hayato,
K. Hiraide,
K. Ieki,
M. Ikeda,
J. Kameda,
Y. Kanemura,
R. Kaneshima,
Y. Kashiwagi,
Y. Kataoka,
S. Miki,
S. Mine,
M. Miura,
S. Moriyama,
Y. Nakano,
M. Nakahata,
S. Nakayama,
Y. Noguchi,
K. Okamoto,
K. Sato,
H. Sekiya,
H. Shiba
, et al. (202 additional authors not shown)
Abstract:
In 2020, the Super-Kamiokande (SK) experiment moved to a new stage (SK-Gd) in which gadolinium (Gd) sulfate octahydrate was added to the water in the detector, enhancing the efficiency to detect thermal neutrons and consequently improving the sensitivity to low energy electron anti-neutrinos from inverse beta decay (IBD) interactions. SK-Gd has the potential to provide early alerts of incipient co…
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In 2020, the Super-Kamiokande (SK) experiment moved to a new stage (SK-Gd) in which gadolinium (Gd) sulfate octahydrate was added to the water in the detector, enhancing the efficiency to detect thermal neutrons and consequently improving the sensitivity to low energy electron anti-neutrinos from inverse beta decay (IBD) interactions. SK-Gd has the potential to provide early alerts of incipient core-collapse supernovae through detection of electron anti-neutrinos from thermal and nuclear processes responsible for the cooling of massive stars before the gravitational collapse of their cores. These pre-supernova neutrinos emitted during the silicon burning phase can exceed the energy threshold for IBD reactions. We present the sensitivity of SK-Gd to pre-supernova stars and the techniques used for the development of a pre-supernova alarm based on the detection of these neutrinos in SK, as well as prospects for future SK-Gd phases with higher concentrations of Gd. For the current SK-Gd phase, high-confidence alerts for Betelgeuse could be issued up to nine hours in advance of the core-collapse itself.
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Submitted 17 August, 2022; v1 submitted 19 May, 2022;
originally announced May 2022.
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Testing Non-Standard Interactions Between Solar Neutrinos and Quarks with Super-Kamiokande
Authors:
Super-Kamiokande Collaboration,
:,
P. Weatherly,
K. Abe,
C. Bronner,
Y. Hayato,
K. Hiraide,
M. Ikeda,
K. Iyogi,
J. Kameda,
Y. Kanemura,
Y. Kataoka,
Y. Kato,
Y. Kishimoto,
S. Miki,
M. Miura,
S. Moriyama,
T. Mochizuki,
M. Nakahata,
Y. Nakano,
S. Nakayama,
T. Okada,
K. Okamoto,
A. Orii,
G. Pronost
, et al. (248 additional authors not shown)
Abstract:
Non-Standard Interactions (NSI) between neutrinos and matter affect the neutrino flavor oscillations. Due to the high matter density in the core of the Sun, solar neutrinos are suited to probe these interactions. Using the $277$ kton-yr exposure of Super-Kamiokande to $^{8}$B solar neutrinos, we search for the presence of NSI. Our data favors the presence of NSI with down quarks at 1.8$σ$, and wit…
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Non-Standard Interactions (NSI) between neutrinos and matter affect the neutrino flavor oscillations. Due to the high matter density in the core of the Sun, solar neutrinos are suited to probe these interactions. Using the $277$ kton-yr exposure of Super-Kamiokande to $^{8}$B solar neutrinos, we search for the presence of NSI. Our data favors the presence of NSI with down quarks at 1.8$σ$, and with up quarks at 1.6$σ$, with the best fit NSI parameters being ($ε_{11}^{d},ε_{12}^{d}$) = (-3.3, -3.1) for $d$-quarks and ($ε_{11}^{u},ε_{12}^{u}$) = (-2.5, -3.1) for $u$-quarks. After combining with data from the Sudbury Neutrino Observatory and Borexino, the significance increases by 0.1$σ$.
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Submitted 22 March, 2022;
originally announced March 2022.
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New Methods and Simulations for Cosmogenic Induced Spallation Removal in Super-Kamiokande-IV
Authors:
Super-Kamiokande Collaboration,
:,
S. Locke,
A. Coffani,
K. Abe,
C. Bronner,
Y. Hayato,
M. Ikeda,
S. Imaizumi,
H. Ito,
J. Kameda,
Y. Kataoka,
M. Miura,
S. Moriyama,
Y. Nagao,
M. Nakahata,
Y. Nakajima,
S. Nakayama,
T. Okada,
K. Okamoto,
A. Orii,
G. Pronost,
H. Sekiya,
M. Shiozawa,
Y. Sonoda
, et al. (196 additional authors not shown)
Abstract:
Radioactivity induced by cosmic muon spallation is a dominant source of backgrounds for $\mathcal{O}(10)~$MeV neutrino interactions in water Cherenkov detectors. In particular, it is crucial to reduce backgrounds to measure the solar neutrino spectrum and find neutrino interactions from distant supernovae. In this paper we introduce new techniques to locate muon-induced hadronic showers and effici…
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Radioactivity induced by cosmic muon spallation is a dominant source of backgrounds for $\mathcal{O}(10)~$MeV neutrino interactions in water Cherenkov detectors. In particular, it is crucial to reduce backgrounds to measure the solar neutrino spectrum and find neutrino interactions from distant supernovae. In this paper we introduce new techniques to locate muon-induced hadronic showers and efficiently reject spallation backgrounds. Applying these techniques to the solar neutrino analysis with an exposure of $2790\times22.5$~kton.day increases the signal efficiency by $12.6\%$, approximately corresponding to an additional year of detector running. Furthermore, we present the first spallation simulation at SK, where we model hadronic interactions using FLUKA. The agreement between the isotope yields and shower pattern in this simulation and in the data gives confidence in the accuracy of this simulation, and thus opens the door to use it to optimize muon spallation removal in new data with gadolinium-enhanced neutron capture detection.
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Submitted 30 November, 2021;
originally announced December 2021.
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Diffuse Supernova Neutrino Background Search at Super-Kamiokande
Authors:
Super-Kamiokande Collaboration,
:,
K. Abe,
C. Bronner,
Y. Hayato,
K. Hiraide,
M. Ikeda,
S. Imaizumi,
J. Kameda,
Y. Kanemura,
Y. Kataoka,
S. Miki,
M. Miura,
S. Moriyama,
Y. Nagao,
M. Nakahata,
S. Nakayama,
T. Okada,
K. Okamoto,
A. Orii,
G. Pronost,
H. Sekiya,
M. Shiozawa,
Y. Sonoda,
Y. Suzuki
, et al. (197 additional authors not shown)
Abstract:
A new search for the diffuse supernova neutrino background (DSNB) flux has been conducted at Super-Kamiokande (SK), with a $22.5\times2970$-kton$\cdot$day exposure from its fourth operational phase IV. The new analysis improves on the existing background reduction techniques and systematic uncertainties and takes advantage of an improved neutron tagging algorithm to lower the energy threshold comp…
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A new search for the diffuse supernova neutrino background (DSNB) flux has been conducted at Super-Kamiokande (SK), with a $22.5\times2970$-kton$\cdot$day exposure from its fourth operational phase IV. The new analysis improves on the existing background reduction techniques and systematic uncertainties and takes advantage of an improved neutron tagging algorithm to lower the energy threshold compared to the previous phases of SK. This allows for setting the world's most stringent upper limit on the extraterrestrial $\barν_e$ flux, for neutrino energies below 31.3 MeV. The SK-IV results are combined with the ones from the first three phases of SK to perform a joint analysis using $22.5\times5823$ kton$\cdot$days of data. This analysis has the world's best sensitivity to the DSNB $\barν_e$ flux, comparable to the predictions from various models. For neutrino energies larger than 17.3 MeV, the new combined $90\%$ C.L. upper limits on the DSNB $\barν_e$ flux lie around $2.7$ cm$^{-2}$$\cdot$$\text{sec}^{-1}$, strongly disfavoring the most optimistic predictions. Finally, potentialities of the gadolinium phase of SK and the future Hyper-Kamiokande experiment are discussed.
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Submitted 2 November, 2021; v1 submitted 23 September, 2021;
originally announced September 2021.
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First Gadolinium Loading to Super-Kamiokande
Authors:
K. Abe,
C. Bronner,
Y. Hayato,
K. Hiraide,
M. Ikeda,
S. Imaizumi,
J. Kameda,
Y. Kanemura,
Y. Kataoka,
S. Miki,
M. Miura,
S. Moriyama,
Y. Nagao,
M. Nakahata,
S. Nakayama,
T. Okada,
K. Okamoto,
A. Orii,
G. Pronost,
H. Sekiya,
M. Shiozawa,
Y. Sonoda,
Y. Suzuki,
A. Takeda,
Y. Takemoto
, et al. (192 additional authors not shown)
Abstract:
In order to improve Super-Kamiokande's neutron detection efficiency and to thereby increase its sensitivity to the diffuse supernova neutrino background flux, 13 tons of $\rm Gd_2(\rm SO_4)_3\cdot \rm 8H_2O$ (gadolinium sulfate octahydrate) was dissolved into the detector's otherwise ultrapure water from July 14 to August 17, 2020, marking the start of the SK-Gd phase of operations. During the loa…
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In order to improve Super-Kamiokande's neutron detection efficiency and to thereby increase its sensitivity to the diffuse supernova neutrino background flux, 13 tons of $\rm Gd_2(\rm SO_4)_3\cdot \rm 8H_2O$ (gadolinium sulfate octahydrate) was dissolved into the detector's otherwise ultrapure water from July 14 to August 17, 2020, marking the start of the SK-Gd phase of operations. During the loading, water was continuously recirculated at a rate of 60 m$^3$/h, extracting water from the top of the detector and mixing it with concentrated $\rm Gd_2(\rm SO_4)_3\cdot \rm 8H_2O$ solution to create a 0.02% solution of the Gd compound before injecting it into the bottom of the detector. A clear boundary between the Gd-loaded and pure water was maintained through the loading, enabling monitoring of the loading itself and the spatial uniformity of the Gd concentration over the 35 days it took to reach the top of the detector. During the subsequent commissioning the recirculation rate was increased to 120 m$^3$/h, resulting in a constant and uniform distribution of Gd throughout the detector and water transparency equivalent to that of previous pure-water operation periods. Using an Am-Be neutron calibration source the mean neutron capture time was measured to be $115\pm1$ $μ$s, which corresponds to a Gd concentration of $111\pm2$ ppm, as expected for this level of Gd loading. This paper describes changes made to the water circulation system for this detector upgrade, the Gd loading procedure, detector commissioning, and the first neutron calibration measurements in SK-Gd.
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Submitted 15 December, 2021; v1 submitted 1 September, 2021;
originally announced September 2021.
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Search for neutrinos in coincidence with gravitational wave events from the LIGO-Virgo O3a Observing Run with the Super-Kamiokande detector
Authors:
The Super-Kamiokande collaboration,
:,
K. Abe,
C. Bronner,
Y. Hayato,
M. Ikeda,
S. Imaizumi,
J. Kameda,
Y. Kanemura,
Y. Kataoka,
S. Miki,
M. Miura,
S. Moriyama,
Y. Nagao,
M. Nakahata,
S. Nakayama,
T. Okada,
K. Okamoto,
A. Orii,
G. Pronost,
H. Sekiya,
M. Shiozawa,
Y. Sonoda,
Y. Suzuki,
A. Takeda
, et al. (189 additional authors not shown)
Abstract:
The Super-Kamiokande detector can be used to search for neutrinos in time coincidence with gravitational waves detected by the LIGO-Virgo Collaboration (LVC). Both low-energy ($7-100$ MeV) and high-energy ($0.1-10^5$ GeV) samples were analyzed in order to cover a very wide neutrino spectrum. Follow-ups of 36 (out of 39) gravitational waves reported in the GWTC-2 catalog were examined; no significa…
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The Super-Kamiokande detector can be used to search for neutrinos in time coincidence with gravitational waves detected by the LIGO-Virgo Collaboration (LVC). Both low-energy ($7-100$ MeV) and high-energy ($0.1-10^5$ GeV) samples were analyzed in order to cover a very wide neutrino spectrum. Follow-ups of 36 (out of 39) gravitational waves reported in the GWTC-2 catalog were examined; no significant excess above the background was observed, with 10 (24) observed neutrinos compared with 4.8 (25.0) expected events in the high-energy (low-energy) samples. A statistical approach was used to compute the significance of potential coincidences. For each observation, p-values were estimated using neutrino direction and LVC sky map ; the most significant event (GW190602_175927) is associated with a post-trial p-value of $7.8\%$ ($1.4σ$). Additionally, flux limits were computed independently for each sample and by combining the samples. The energy emitted as neutrinos by the identified gravitational wave sources was constrained, both for given flavors and for all-flavors assuming equipartition between the different flavors, independently for each trigger and by combining sources of the same nature.
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Submitted 13 September, 2021; v1 submitted 19 April, 2021;
originally announced April 2021.
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Supernova Model Discrimination with Hyper-Kamiokande
Authors:
Hyper-Kamiokande Collaboration,
:,
K. Abe,
P. Adrich,
H. Aihara,
R. Akutsu,
I. Alekseev,
A. Ali,
F. Ameli,
I. Anghel,
L. H. V. Anthony,
M. Antonova,
A. Araya,
Y. Asaoka,
Y. Ashida,
V. Aushev,
F. Ballester,
I. Bandac,
M. Barbi,
G. J. Barker,
G. Barr,
M. Batkiewicz-Kwasniak,
M. Bellato,
V. Berardi,
M. Bergevin
, et al. (478 additional authors not shown)
Abstract:
Core-collapse supernovae are among the most magnificent events in the observable universe. They produce many of the chemical elements necessary for life to exist and their remnants -- neutron stars and black holes -- are interesting astrophysical objects in their own right. However, despite millennia of observations and almost a century of astrophysical study, the explosion mechanism of core-colla…
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Core-collapse supernovae are among the most magnificent events in the observable universe. They produce many of the chemical elements necessary for life to exist and their remnants -- neutron stars and black holes -- are interesting astrophysical objects in their own right. However, despite millennia of observations and almost a century of astrophysical study, the explosion mechanism of core-collapse supernovae is not yet well understood. Hyper-Kamiokande is a next-generation neutrino detector that will be able to observe the neutrino flux from the next galactic core-collapse supernova in unprecedented detail. We focus on the first 500 ms of the neutrino burst, corresponding to the accretion phase, and use a newly-developed, high-precision supernova event generator to simulate Hyper-Kamiokande's response to five different supernova models. We show that Hyper-Kamiokande will be able to distinguish between these models with high accuracy for a supernova at a distance of up to 100 kpc. Once the next galactic supernova happens, this ability will be a powerful tool for guiding simulations towards a precise reproduction of the explosion mechanism observed in nature.
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Submitted 20 July, 2021; v1 submitted 13 January, 2021;
originally announced January 2021.
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Search for Tens of MeV Neutrinos associated with Gamma-Ray Bursts in Super-Kamiokande
Authors:
The Super-Kamiokande Collaboration,
A. Orii,
K. Abe,
C. Bronner,
Y. Hayato,
M. Ikeda,
S. Imaizumi,
H. Ito,
J. Kameda,
Y. Kataoka,
Y. Kato,
Y. Kishimoto,
M. Miura,
S. Moriyama,
T. Mochizuki,
Y. Nagao,
M. Nakahata,
Y. Nakajima,
S. Nakayama,
T. Okada,
K. Okamoto,
G. Pronost,
H. Sekiya,
M. Shiozawa,
Y. Sonoda
, et al. (195 additional authors not shown)
Abstract:
A search for neutrinos produced in coincidence with Gamma-Ray Bursts(GRB) was conducted with the Super-Kamiokande (SK) detector. Between December 2008 and March 2017, the Gamma-ray Coordinates Network recorded 2208 GRBs that occurred during normal SK operation. Several time windows around each GRB were used to search for coincident neutrino events. No statistically significant signal in excess of…
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A search for neutrinos produced in coincidence with Gamma-Ray Bursts(GRB) was conducted with the Super-Kamiokande (SK) detector. Between December 2008 and March 2017, the Gamma-ray Coordinates Network recorded 2208 GRBs that occurred during normal SK operation. Several time windows around each GRB were used to search for coincident neutrino events. No statistically significant signal in excess of the estimated backgrounds was detected. The $\barν_e$ fluence in the range from 8 MeV to 100 MeV in positron total energy for $\barν_e+p\rightarrow e^{+}+n$ was found to be less than $\rm 5.07\times10^5$ cm$^{-2}$ per GRB in 90\% C.L. Upper bounds on the fluence as a function of neutrino energy were also obtained.
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Submitted 26 June, 2021; v1 submitted 10 January, 2021;
originally announced January 2021.
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Improved method for measuring low concentration radium and its application to the Super-Kamiokande Gadolinium project
Authors:
S. Ito,
K. Ichimura,
Y. Takaku,
K. Abe,
M. Harada,
M. Ikeda,
H. Ito,
Y. Kishimoto,
Y. Nakajima,
T. Okada,
H. Sekiya
Abstract:
Chemical extraction using a molecular recognition resin named "Empore Radium Rad Disk" was developed to improve sensitivity for the low concentration of radium (Ra). Compared with the previous method, the extraction process speed was improved by a factor of three and the recovery rate for $^{226}$Ra was also improved from 81$\pm$4% to $>$99.9%. The sensitivity on the 10$^{-1}$ mBq level was achiev…
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Chemical extraction using a molecular recognition resin named "Empore Radium Rad Disk" was developed to improve sensitivity for the low concentration of radium (Ra). Compared with the previous method, the extraction process speed was improved by a factor of three and the recovery rate for $^{226}$Ra was also improved from 81$\pm$4% to $>$99.9%. The sensitivity on the 10$^{-1}$ mBq level was achieved using a high purity germanium detector. This improved method was applied to determine $^{226}$Ra in Gd$_2$(SO$_4$)$_3{\cdot}$8H$_2$O which will be used in the Super-Kamiokande Gadolinium project. The improvement and measurement results are reported in this paper.
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Submitted 17 June, 2020;
originally announced June 2020.
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Search for Astronomical Neutrinos from Blazar TXS0506+056 in Super-Kamiokande
Authors:
K. Hagiwara,
K. Abe,
C. Bronner,
Y. Hayato,
M. Ikeda,
H. Ito,
J. Kameda,
Y. Kataoka,
Y. Kato,
Y. Kishimoto,
Ll. Marti,
M. Miura,
S. Moriyama,
T. Mochizuki,
M. Nakahata,
Y. Nakajima,
S. Nakayama,
T. Okada,
K. Okamoto,
A. Orii,
G. Pronost,
H. Sekiya,
M. Shiozawa,
Y. Sonoda,
A. Takeda
, et al. (148 additional authors not shown)
Abstract:
We report a search for astronomical neutrinos in the energy region from several GeV to TeV in the direction of the blazar TXS0506+056 using the Super-Kamiokande detector following the detection of a 100 TeV neutrino from the same location by the IceCube collaboration. Using Super-Kamiokande neutrino data across several data samples observed from April 1996 to February 2018 we have searched for bot…
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We report a search for astronomical neutrinos in the energy region from several GeV to TeV in the direction of the blazar TXS0506+056 using the Super-Kamiokande detector following the detection of a 100 TeV neutrino from the same location by the IceCube collaboration. Using Super-Kamiokande neutrino data across several data samples observed from April 1996 to February 2018 we have searched for both a total excess above known backgrounds across the entire period as well as localized excesses on smaller time scales in that interval. No significant excess nor significant variation in the observed event rate are found in the blazar direction. Upper limits are placed on the electron and muon neutrino fluxes at 90\% confidence level as $6.03 \times 10^{-7}$ and $4.52 \times 10^{-7}$ to $9.26 \times 10^{-10}$ [${\rm erg}/{\rm cm}^2/{\rm s}$], respectively.
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Submitted 18 November, 2019; v1 submitted 16 October, 2019;
originally announced October 2019.
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Sensitivity of Super-Kamiokande with Gadolinium to Low Energy Anti-neutrinos from Pre-supernova Emission
Authors:
C. Simpson,
K. Abe,
C. Bronner,
Y. Hayato,
M. Ikeda,
H. Ito,
K. Iyogi,
J. Kameda,
Y. Kataoka,
Y. Kato,
Y. Kishimoto,
Ll. Marti,
M. Miura,
S. Moriyama,
T. Mochizuki,
M. Nakahata,
Y. Nakajima,
S. Nakayama,
T. Okada,
K. Okamoto,
A. Orii,
G. Pronost,
H. Sekiya,
M. Shiozawa,
Y. Sonoda
, et al. (165 additional authors not shown)
Abstract:
Supernova detection is a major objective of the Super-Kamiokande (SK) experiment. In the next stage of SK (SK-Gd), gadolinium (Gd) sulfate will be added to the detector, which will improve the ability of the detector to identify neutrons. A core-collapse supernova will be preceded by an increasing flux of neutrinos and anti-neutrinos, from thermal and weak nuclear processes in the star, over a tim…
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Supernova detection is a major objective of the Super-Kamiokande (SK) experiment. In the next stage of SK (SK-Gd), gadolinium (Gd) sulfate will be added to the detector, which will improve the ability of the detector to identify neutrons. A core-collapse supernova will be preceded by an increasing flux of neutrinos and anti-neutrinos, from thermal and weak nuclear processes in the star, over a timescale of hours; some of which may be detected at SK-Gd. This could provide an early warning of an imminent core-collapse supernova, hours earlier than the detection of the neutrinos from core collapse. Electron anti-neutrino detection will rely on inverse beta decay events below the usual analysis energy threshold of SK, so Gd loading is vital to reduce backgrounds while maximising detection efficiency. Assuming normal neutrino mass ordering, more than 200 events could be detected in the final 12 hours before core collapse for a 15-25 solar mass star at around 200 pc, which is representative of the nearest red supergiant to Earth, $\mathrmα$Ori (Betelgeuse). At a statistical false alarm rate of 1 per century, detection could be up to 10 hours before core collapse, and a pre-supernova star could be detected by SK-Gd up to 600 pc away. A pre-supernova alert could be provided to the astrophysics community following gadolinium loading.
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Submitted 26 September, 2019; v1 submitted 20 August, 2019;
originally announced August 2019.
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Hyper-Kamiokande Design Report
Authors:
Hyper-Kamiokande Proto-Collaboration,
:,
K. Abe,
Ke. Abe,
H. Aihara,
A. Aimi,
R. Akutsu,
C. Andreopoulos,
I. Anghel,
L. H. V. Anthony,
M. Antonova,
Y. Ashida,
V. Aushev,
M. Barbi,
G. J. Barker,
G. Barr,
P. Beltrame,
V. Berardi,
M. Bergevin,
S. Berkman,
L. Berns,
T. Berry,
S. Bhadra,
D. Bravo-Berguño,
F. d. M. Blaszczyk
, et al. (291 additional authors not shown)
Abstract:
On the strength of a double Nobel prize winning experiment (Super)Kamiokande and an extremely successful long baseline neutrino programme, the third generation Water Cherenkov detector, Hyper-Kamiokande, is being developed by an international collaboration as a leading worldwide experiment based in Japan. The Hyper-Kamiokande detector will be hosted in the Tochibora mine, about 295 km away from th…
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On the strength of a double Nobel prize winning experiment (Super)Kamiokande and an extremely successful long baseline neutrino programme, the third generation Water Cherenkov detector, Hyper-Kamiokande, is being developed by an international collaboration as a leading worldwide experiment based in Japan. The Hyper-Kamiokande detector will be hosted in the Tochibora mine, about 295 km away from the J-PARC proton accelerator research complex in Tokai, Japan. The currently existing accelerator will be steadily upgraded to reach a MW beam by the start of the experiment. A suite of near detectors will be vital to constrain the beam for neutrino oscillation measurements. A new cavern will be excavated at the Tochibora mine to host the detector. The experiment will be the largest underground water Cherenkov detector in the world and will be instrumented with new technology photosensors, faster and with higher quantum efficiency than the ones in Super-Kamiokande. The science that will be developed will be able to shape the future theoretical framework and generations of experiments. Hyper-Kamiokande will be able to measure with the highest precision the leptonic CP violation that could explain the baryon asymmetry in the Universe. The experiment also has a demonstrated excellent capability to search for proton decay, providing a significant improvement in discovery sensitivity over current searches for the proton lifetime. The atmospheric neutrinos will allow to determine the neutrino mass ordering and, together with the beam, able to precisely test the three-flavour neutrino oscillation paradigm and search for new phenomena. A strong astrophysical programme will be carried out at the experiment that will detect supernova neutrinos and will measure precisely solar neutrino oscillation.
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Submitted 28 November, 2018; v1 submitted 9 May, 2018;
originally announced May 2018.
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Search for Neutrinos in Super-Kamiokande associated with the GW170817 neutron-star merger
Authors:
K. Abe,
C. Bronner,
Y. Hayato,
M. Ikeda,
K. Iyogi,
J. Kameda,
Y. Kato,
Y. Kishimoto,
Ll. Marti,
M. Miura,
S. Moriyama,
M. Nakahata,
Y. Nakajima,
Y. Nakano,
S. Nakayama,
A. Orii,
G. Pronost,
H. Sekiya,
M. Shiozawa,
Y. Sonoda,
A. Takeda,
A. Takenaka,
H. Tanaka,
S. Tasaka,
T. Yano
, et al. (138 additional authors not shown)
Abstract:
We report the results of a neutrino search in Super-Kamiokande for coincident signals with the first detected gravitational wave produced by a binary neutron star merger, GW170817, which was followed by a short gamma-ray burst, GRB170817A, and a kilonova/macronova. We searched for coincident neutrino events in the range from 3.5 MeV to $\sim$100 PeV, in a time window $\pm$500 seconds around the gr…
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We report the results of a neutrino search in Super-Kamiokande for coincident signals with the first detected gravitational wave produced by a binary neutron star merger, GW170817, which was followed by a short gamma-ray burst, GRB170817A, and a kilonova/macronova. We searched for coincident neutrino events in the range from 3.5 MeV to $\sim$100 PeV, in a time window $\pm$500 seconds around the gravitational wave detection time, as well as during a 14-day period after the detection. No significant neutrino signal was observed for either time window. We calculated 90% confidence level upper limits on the neutrino fluence for GW170817. From the upward-going-muon events in the energy region above 1.6 GeV, the neutrino fluence limit is $16.0^{+0.7}_{-0.6}$ ($21.3^{+1.1}_{-0.8}$) cm$^{-2}$ for muon neutrinos (muon antineutrinos), with an error range of $\pm5^{\circ}$ around the zenith angle of NGC4993, and the energy spectrum is under the assumption of an index of $-2$. The fluence limit for neutrino energies less than 100 MeV, for which the emission mechanism would be different than for higher-energy neutrinos, is also calculated. It is $6.6 \times 10^7$ cm$^{-2}$ for anti-electron neutrinos under the assumption of a Fermi-Dirac spectrum with average energy of 20 MeV.
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Submitted 29 March, 2018; v1 submitted 12 February, 2018;
originally announced February 2018.
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Search for an excess of events in the Super-Kamiokande detector in the directions of the astrophysical neutrinos reported by the IceCube Collaboration
Authors:
The Super-Kamiokande Collaboration,
:,
K. Abe,
C. Bronner,
G. Pronost,
Y. Hayato,
M. Ikeda,
K. Iyogi,
J. Kameda,
Y. Kato,
Y. Kishimoto,
Ll. Marti,
M. Miura,
S. Moriyama,
M. Nakahata,
Y. Nakano,
S. Nakayama,
Y. Okajima,
A. Orii,
H. Sekiya,
M. Shiozawa,
Y. Sonoda,
A. Takeda,
A. Takenaka,
H. Tanaka
, et al. (139 additional authors not shown)
Abstract:
We present the results of a search in the Super-Kamiokande (SK) detector for excesses of neutrinos with energies above a few GeV that are in the direction of the track events reported in IceCube. Data from all SK phases (SK-I through SK-IV) were used, spanning a period from April 1996 to April 2016 and corresponding to an exposure of 225 kilotonne-years . We considered the 14 IceCube track events…
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We present the results of a search in the Super-Kamiokande (SK) detector for excesses of neutrinos with energies above a few GeV that are in the direction of the track events reported in IceCube. Data from all SK phases (SK-I through SK-IV) were used, spanning a period from April 1996 to April 2016 and corresponding to an exposure of 225 kilotonne-years . We considered the 14 IceCube track events from a data set with 1347 livetime days taken from 2010 to 2014. We use Poisson counting to determine if there is an excess of neutrinos detected in SK in a 10 degree search cone (5 degrees for the highest energy data set) around the reconstructed direction of the IceCube event. No significant excess was found in any of the search directions we examined. We also looked for coincidences with a recently reported IceCube multiplet event. No events were detected within a $\pm$ 500 s time window around the first detected event, and no significant excess was seen from that direction over the lifetime of SK.
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Submitted 5 January, 2018; v1 submitted 26 July, 2017;
originally announced July 2017.
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Search for Neutrinos in Super-Kamiokande associated with Gravitational Wave Events GW150914 and GW151226
Authors:
K. Abe,
K. Haga,
Y. Hayato,
M. Ikeda,
K. Iyogi,
J. Kameda,
Y. Kishimoto,
M. Miura,
S. Moriyama,
M. Nakahata,
T. Nakajima,
Y. Nakano,
S. Nakayama,
A. Orii,
H. Sekiya,
M. Shiozawa,
A. Takeda,
H. Tanaka,
S. Tasaka,
T. Tomura,
R. Akutsu,
T. Kajita,
K. Kaneyuki,
Y. Nishimura,
E. Richard
, et al. (108 additional authors not shown)
Abstract:
We report the results from a search in Super-Kamiokande for neutrino signals coincident with the first detected gravitational wave events, GW150914 and GW151226, using a neutrino energy range from 3.5 MeV to 100 PeV. We searched for coincident neutrino events within a time window of $\pm$500 seconds around the gravitational wave detection time. Four neutrino candidates are found for GW150914 and n…
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We report the results from a search in Super-Kamiokande for neutrino signals coincident with the first detected gravitational wave events, GW150914 and GW151226, using a neutrino energy range from 3.5 MeV to 100 PeV. We searched for coincident neutrino events within a time window of $\pm$500 seconds around the gravitational wave detection time. Four neutrino candidates are found for GW150914 and no candidates are found for GW151226. The remaining neutrino candidates are consistent with the expected background events. We calculated the 90\% confidence level upper limits on the combined neutrino fluence for both gravitational wave events, which depends on event energy and topologies. Considering the upward going muon data set (1.6 GeV - 100 PeV) the neutrino fluence limit for each gravitational wave event is 14 - 37 (19 - 50) cm$^{-2}$ for muon neutrinos (muon antineutrinos), depending on the zenith angle of the event. In the other data sets, the combined fluence limits for both gravitational wave events range from 2.4$\times 10^{4}$ to 7.0$\times 10^{9}$ cm$^{-2}$.
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Submitted 31 August, 2016;
originally announced August 2016.
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Real-Time Supernova Neutrino Burst Monitor at Super-Kamiokande
Authors:
K. Abe,
Y. Haga,
Y. Hayato,
M. Ikeda,
K. Iyogi,
J. Kameda,
Y. Kishimoto,
M. Miura,
S. Moriyama,
M. Nakahata,
Y. Nakano,
S. Nakayama,
H. Sekiya,
M. Shiozawa,
Y. Suzuki,
A. Takeda,
H. Tanaka,
T. Tomura,
K. Ueno,
R. A. Wendell,
T. Yokozawa,
T. Irvine,
T. Kajita,
I. Kametani,
K. Kaneyuki
, et al. (102 additional authors not shown)
Abstract:
We present a real-time supernova neutrino burst monitor at Super-Kamiokande (SK). Detecting supernova explosions by neutrinos in real time is crucial for giving a clear picture of the explosion mechanism. Since the neutrinos are expected to come earlier than light, a fast broadcasting of the detection may give astronomers a chance to make electromagnetic radiation observations of the explosions ri…
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We present a real-time supernova neutrino burst monitor at Super-Kamiokande (SK). Detecting supernova explosions by neutrinos in real time is crucial for giving a clear picture of the explosion mechanism. Since the neutrinos are expected to come earlier than light, a fast broadcasting of the detection may give astronomers a chance to make electromagnetic radiation observations of the explosions right at the onset. The role of the monitor includes a fast announcement of the neutrino burst detection to the world and a determination of the supernova direction. We present the online neutrino burst detection system and studies of the direction determination accuracy based on simulations at SK.
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Submitted 11 April, 2016; v1 submitted 18 January, 2016;
originally announced January 2016.
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Measurements of the atmospheric neutrino flux by Super-Kamiokande: energy spectra, geomagnetic effects, and solar modulation
Authors:
E. Richard,
K. Okumura,
K. Abe,
Y. Haga,
Y. Hayato,
M. Ikeda,
K. Iyogi,
J. Kameda,
Y. Kishimoto,
M. Miura,
S. Moriyama,
M. Nakahata,
T. Nakajima,
Y. Nakano,
S. Nakayama,
A. Orii,
H. Sekiya,
M. Shiozawa,
A. Takeda,
H. Tanaka,
T. Tomura,
R. A. Wendell,
R. Akutsu,
T. Irvine,
T. Kajita
, et al. (104 additional authors not shown)
Abstract:
A comprehensive study on the atmospheric neutrino flux in the energy region from sub-GeV up to several TeV using the Super-Kamiokande water Cherenkov detector is presented in this paper. The energy and azimuthal spectra of the atmospheric $ν_e+{\barν}_e$ and $ν_μ+{\barν}_μ$ fluxes are measured. The energy spectra are obtained using an iterative unfolding method by combining various event topologie…
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A comprehensive study on the atmospheric neutrino flux in the energy region from sub-GeV up to several TeV using the Super-Kamiokande water Cherenkov detector is presented in this paper. The energy and azimuthal spectra of the atmospheric $ν_e+{\barν}_e$ and $ν_μ+{\barν}_μ$ 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 $ν_e$ and $ν_μ$ samples at 8.0 σ and 6.0 σ significance, respectively, and an indication that the asymmetry dipole angle changes depending on the zenith angle was seen at the 2.2 σ 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 also performed, and a weak indication of a correlation was seen at the 1.1 σ level, using SK I-IV data spanning a 20 year period. For particularly strong solar activity periods known as Forbush decreases, no theoretical prediction is available, but a deviation below the typical neutrino event rate is seen at the 2.4 σ level.
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Submitted 6 September, 2016; v1 submitted 27 October, 2015;
originally announced October 2015.
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Calibration of the Super-Kamiokande Detector
Authors:
K. Abe,
Y. Hayato,
T. Iida,
K. Iyogi,
J. Kameda,
Y. Kishimoto,
Y. Koshio,
Ll. Marti,
M. Miura,
S. Moriyama,
M. Nakahata,
Y. Nakano,
S. Nakayama,
Y. Obayashi,
H. Sekiya,
M. Shiozawa,
Y. Suzuki,
A. Takeda,
Y. Takenaga,
H. Tanaka,
T. Tomura,
K. Ueno,
R. A. Wendell,
T. Yokozawa,
T. J. Irvine
, et al. (108 additional authors not shown)
Abstract:
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 th…
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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 the modeling of the detector in our Monte Carlo simulation, including in particular the optical properties of its water target and their variability over time. Detailed studies on the water quality are also presented. As a result of this work, we achieved a precision sufficient for physics analysis over a wide energy range (from a few MeV to above a TeV). For example, the charge determination was understood at the 1% level, and the timing resolution was 2.1 nsec at the one-photoelectron charge level and 0.5 nsec at the 100-photoelectron charge level.
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Submitted 20 December, 2013; v1 submitted 29 June, 2013;
originally announced July 2013.
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Search for GUT Monopoles at Super-Kamiokande
Authors:
The Super-Kamiokande Collaboration,
:,
K. Ueno,
K. Abe,
Y. Hayato,
T. Iida,
K. Iyogi,
J. Kameda,
Y. Koshio,
Y. Kozuma,
M. Miura,
S. Moriyama,
M. Nakahata,
S. Nakayama,
Y. Obayashi,
H. Sekiya,
M. Shiozawa,
Y. Suzuki,
A. Takeda,
Y. Takenaga,
K. Ueshima,
S. Yamada,
T. Yokozawa,
K. Martens,
J. Schuemann
, et al. (88 additional authors not shown)
Abstract:
GUT monopoles captured by the Sun's gravitation are expected to catalyze proton decays via the Callan-Rubakov process. In this scenario, protons, which initially decay into pions, will ultimately produce ν_{e}, ν_μ and \barν_μ. After undergoing neutrino oscillation, all neutrino species appear when they arrive at the Earth, and can be detected by a 50,000 metric ton water Cherenkov detector, Super…
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GUT monopoles captured by the Sun's gravitation are expected to catalyze proton decays via the Callan-Rubakov process. In this scenario, protons, which initially decay into pions, will ultimately produce ν_{e}, ν_μ and \barν_μ. After undergoing neutrino oscillation, all neutrino species appear when they arrive at the Earth, and can be detected by a 50,000 metric ton water Cherenkov detector, Super-Kamiokande (SK). A search for low energy neutrinos in the electron total energy range from 19 to 55 MeV was carried out with SK and gives a monopole flux limit of F_M(σ_0/1 mb) < 6.3 \times 10^{-24} (β_M/10^{-3})^2 cm^{-2} s^{-1} sr^{-1} at 90% C.L., where β_M is the monopole velocity in units of the speed of light and σ_0 is the catalysis cross section at β_M=1. The obtained limit is more than eight orders of magnitude more stringent than the current best cosmic-ray supermassive monopole flux limit, F_M < 1 \times 10^{-15} cm^{-2} s^{-1} sr^{-1} for β_M < 10^{-3} and also two orders of magnitude lower than the result of the Kamiokande experiment, which used a similar detection method.
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Submitted 5 March, 2012;
originally announced March 2012.
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Constraints on a vacuum energy from both SNIa and CMB temperature observations
Authors:
Riou Nakamura,
E. P. Berni Ann Thushari,
Mikio Ikeda,
Masa-aki Hashimoto
Abstract:
We investigate the cosmic thermal evolution with a vacuum energy which decays into photon at the low-redshift. We assume that the vacuum energy is a function of the scale factor that increases toward the early universe. We put on the constraints using recent observations of both type Ia supernovae (SNIa) by Union-2 compilation and the cosmic microwave background (CMB) temperature at the range of t…
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We investigate the cosmic thermal evolution with a vacuum energy which decays into photon at the low-redshift. We assume that the vacuum energy is a function of the scale factor that increases toward the early universe. We put on the constraints using recent observations of both type Ia supernovae (SNIa) by Union-2 compilation and the cosmic microwave background (CMB) temperature at the range of the redshift 0.01 < z < 3. From SNIa, we find that the effects of a decaying vacuum energy on the cosmic expansion rate should be very small but could be possible for z < 1.5. On the other hand, we obtain the severe constraints for parameters from the CMB temperature observations. Although the temperature can be still lower than the case of the standard cosmological model, it should only affect the thermal evolution at the early epoch.
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Submitted 27 April, 2012; v1 submitted 13 December, 2011;
originally announced December 2011.
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Letter of Intent: The Hyper-Kamiokande Experiment --- Detector Design and Physics Potential ---
Authors:
K. Abe,
T. Abe,
H. Aihara,
Y. Fukuda,
Y. Hayato,
K. Huang,
A. K. Ichikawa,
M. Ikeda,
K. Inoue,
H. Ishino,
Y. Itow,
T. Kajita,
J. Kameda,
Y. Kishimoto,
M. Koga,
Y. Koshio,
K. P. Lee,
A. Minamino,
M. Miura,
S. Moriyama,
M. Nakahata,
K. Nakamura,
T. Nakaya,
S. Nakayama,
K. Nishijima
, et al. (16 additional authors not shown)
Abstract:
We propose the Hyper-Kamiokande (Hyper-K) detector as a next generation underground water Cherenkov detector. It will serve as a far detector of a long baseline neutrino oscillation experiment envisioned for the upgraded J-PARC, and as a detector capable of observing -- far beyond the sensitivity of the Super-Kamiokande (Super-K) detector -- proton decays, atmospheric neutrinos, and neutrinos from…
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We propose the Hyper-Kamiokande (Hyper-K) detector as a next generation underground water Cherenkov detector. It will serve as a far detector of a long baseline neutrino oscillation experiment envisioned for the upgraded J-PARC, and as a detector capable of observing -- far beyond the sensitivity of the Super-Kamiokande (Super-K) detector -- proton decays, atmospheric neutrinos, and neutrinos from astronomical origins. The baseline design of Hyper-K is based on the highly successful Super-K, taking full advantage of a well-proven technology. (to be continued)
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Submitted 15 September, 2011;
originally announced September 2011.
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An Indirect Search for WIMPs in the Sun using 3109.6 days of upward-going muons in Super-Kamiokande
Authors:
The Super-Kamiokande Collaboration,
:,
T. Tanaka,
K. Abe,
Y. Hayato,
T. Iida,
J. Kameda,
Y. Koshio,
Y. Kouzuma,
M. Miura,
S. Moriyama,
M. Nakahata,
S. Nakayama,
Y. Obayashi,
H. Sekiya,
M. Shiozawa,
Y. Suzuki,
A. Takeda,
Y. Takenaga,
K. Ueno,
K. Ueshima,
S. Yamada,
T. Yokozawa,
C. Ishihara,
S. Hazama
, et al. (89 additional authors not shown)
Abstract:
We present the result of an indirect search for high energy neutrinos from WIMP annihilation in the Sun using upward-going muon (upmu) events at Super-Kamiokande. Datasets from SKI-SKIII (3109.6 days) were used for the analysis. We looked for an excess of neutrino signal from the Sun as compared with the expected atmospheric neutrino background in three upmu categories: stopping, non-showering, an…
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We present the result of an indirect search for high energy neutrinos from WIMP annihilation in the Sun using upward-going muon (upmu) events at Super-Kamiokande. Datasets from SKI-SKIII (3109.6 days) were used for the analysis. We looked for an excess of neutrino signal from the Sun as compared with the expected atmospheric neutrino background in three upmu categories: stopping, non-showering, and showering. No significant excess was observed. The 90% C.L. upper limits of upward-going muon flux induced by WIMPs of 100 GeV/c$^2$ were 6.4$\times10^{-15}$ cm$^{-2}$ sec$^{-1}$ and 4.0$\times10^{-15}$ cm$^{-2}$ sec$^{-1}$ for the soft and hard annihilation channels, respectively. These limits correspond to upper limits of 4.5$\times10^{-39}$ cm$^{-2}$ and 2.7$\times10^{-40}$ cm$^{-2}$ for spin-dependent WIMP-nucleon scattering cross sections in the soft and hard annihilation channels, respectively.
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Submitted 31 July, 2012; v1 submitted 16 August, 2011;
originally announced August 2011.
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Warm and Dense Molecular Gas in the N159 Region: 12CO J=4-3 and 13CO J=3-2 Observations with NANTEN2 and ASTE
Authors:
Yoji Mizuno,
Akiko Kawamura,
Toshikazu Onishi,
Tetsuhiro Minamidani,
Erik Muller,
Hiroaki Yamamoto,
Takahiro Hayakawa,
Norikazu Mizuno,
Akira Mizuno,
Jurgen Stutzki,
Jorge L. Pineda,
Uli Klein,
Frank Bertoldi,
Bon-Chul Koo,
Monica Rubio,
Michael Burton,
Arnold Benz,
Hajime Ezawa,
Nobuyuki Yamaguchi,
Kotaro Kohno,
Tetsuo Hasegawa,
Ken'ichi Tatematsu,
Masafumi Ikeda,
Jurgen Ott,
Tony Wong
, et al. (7 additional authors not shown)
Abstract:
New 12CO J=4-3 and 13CO J=3-2 observations of the N159 region in the Large Magellanic Cloud have been made. The 12CO J=4-3 distribution is separated into three clumps. These new measurements toward the three clumps are used in coupled calculations of molecular rotational excitation and line radiation transfer, along with other transitions of the 12CO as well as the isotope transitions of 13CO. T…
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New 12CO J=4-3 and 13CO J=3-2 observations of the N159 region in the Large Magellanic Cloud have been made. The 12CO J=4-3 distribution is separated into three clumps. These new measurements toward the three clumps are used in coupled calculations of molecular rotational excitation and line radiation transfer, along with other transitions of the 12CO as well as the isotope transitions of 13CO. The temperatures and densities are determined to be ~70-80K and ~3x10^3 cm-3 in N159W and N159E and ~30K and ~1.6x10^3 cm-3 in N159S. These results are compared with the star formation activity. The N159E clump is associated with embedded cluster(s) as observed at 24 micron and the derived high temperature is explained as due to the heating by these sources. The N159E clump is likely responsible for a dark lane in a large HII region by the dust extinction. The N159W clump is associated with embedded clusters mainly toward the eastern edge of the clump only. These clusters show offsets of 20"-40" from the 12CO J=4-3 peak and are probably responsible for heating indicated by the derived high temperature. The N159W clump exhibits no sign of star formation toward the 12CO J=4-3 peak position and its western region. We suggest that the N159W peak represents a pre-star-cluster core of ~105M_sol which deserves further detailed studies. Note that recent star formation took place between N159W and N159E as indicated by several star clusters and HII regions, while the natal molecular gas toward the stars have already been dissipated by the ionization and stellar winds of the OB stars. The N159S clump shows little sign of star formation as is consistent with the lower temperature and somewhat lower density. The N159S clump is also a candidate for future star formation.
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Submitted 1 October, 2009;
originally announced October 2009.
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Sub-millimeter Observations of Giant Molecular Clouds in the Large Magellanic Cloud: Temperature and Density as Determined from J=3-2 and J=1-0 transitions of CO
Authors:
T. Minamidani,
N. Mizuno,
Y. Mizuno,
A. Kawamura,
T. Onishi,
T. Hasegawa,
K. Tatematsu,
M. Ikeda,
Y. Moriguchi,
N. Yamaguchi,
J. Ott,
T. Wong,
E. Muller,
J. L. Pineda,
A. Hughes,
L. Staveley-Smith,
U. Klein,
A. Mizuno,
S. Nikolić,
R. S. Booth,
A. Heikkilä,
L. -A. Nyman,
M. Lerner,
G. Garay,
S. Kim
, et al. (4 additional authors not shown)
Abstract:
We have carried out sub-mm 12CO(J=3-2) observations of 6 giant molecular clouds (GMCs) in the Large Magellanic Cloud (LMC) with the ASTE 10m sub-mm telescope at a spatial resolution of 5 pc and very high sensitivity. We have identified 32 molecular clumps in the GMCs and revealed significant details of the warm and dense molecular gas with n(H2) $\sim$ 10$^{3-5}$ cm$^{-3}$ and Tkin $\sim$ 60 K.…
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We have carried out sub-mm 12CO(J=3-2) observations of 6 giant molecular clouds (GMCs) in the Large Magellanic Cloud (LMC) with the ASTE 10m sub-mm telescope at a spatial resolution of 5 pc and very high sensitivity. We have identified 32 molecular clumps in the GMCs and revealed significant details of the warm and dense molecular gas with n(H2) $\sim$ 10$^{3-5}$ cm$^{-3}$ and Tkin $\sim$ 60 K. These data are combined with 12CO(J=1-0) and 13CO(J=1-0) results and compared with LVG calculations. We found that the ratio of 12CO(J=3-2) to 12CO(J=1-0) emission is sensitive to and is well correlated with the local Halpha flux. We interpret that differences of clump propeties represent an evolutionary sequence of GMCs in terms of density increase leading to star formation.Type I and II GMCs (starless GMCs and GMCs with HII regions only, respectively) are at the young phase of star formation where density does not yet become high enough to show active star formation and Type III GMCs (GMCs with HII regions and young star clusters) represents the later phase where the average density is increased and the GMCs are forming massive stars. The high kinetic temperature correlated with \Halpha flux suggests that FUV heating is dominant in the molecular gas of the LMC.
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Submitted 23 October, 2007;
originally announced October 2007.
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Search for Supernova Neutrino Bursts at Super-Kamiokande
Authors:
Super-Kamiokande Collaboration,
:,
M. Ikeda,
A. Takeda,
Y. Fukuda,
M. R. Vagins
Abstract:
The result of a search for neutrino bursts from supernova explosions using the Super-Kamiokande detector is reported. Super-Kamiokande is sensitive to core-collapse supernova explosions via observation of their neutrino emissions. The expected number of events comprising such a burst is ~10^4 and the average energy of the neutrinos is in few tens of MeV range in the case of a core-collapse super…
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The result of a search for neutrino bursts from supernova explosions using the Super-Kamiokande detector is reported. Super-Kamiokande is sensitive to core-collapse supernova explosions via observation of their neutrino emissions. The expected number of events comprising such a burst is ~10^4 and the average energy of the neutrinos is in few tens of MeV range in the case of a core-collapse supernova explosion at the typical distance in our galaxy (10 kiloparsecs); this large signal means that the detection efficiency anywhere within our galaxy and well past the Magellanic Clouds is 100%. We examined a data set which was taken from May, 1996 to July, 2001 and from December, 2002 to October, 2005 corresponding to 2589.2 live days. However, there is no evidence of such a supernova explosion during the data-taking period. The 90% C.L. upper limit on the rate of core-collapse supernova explosions out to distances of 100 kiloparsecs is found to be 0.32 SN/year.
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Submitted 15 June, 2007;
originally announced June 2007.
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Mapping Observations of DNC and HN^13C in Dark Cloud Cores
Authors:
T. Hirota,
M. Ikeda,
S. Yamamoto
Abstract:
We present results of mapping observations of the DNC, HN^13C, and H^13CO^+ lines (J=1-0) toward 4 nearby dark cloud cores, TMC-1, L1512, L1544, and L63, along with observations of the DNC and HN^13C lines (J=2-1) toward selected positions. By use of statistical equilibrium calculations based on the LVG model, the H_2 densities are derived to be (1.4-5.5)*10^5 cm^-3, and the [DNC]/[HN^13C] ratio…
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We present results of mapping observations of the DNC, HN^13C, and H^13CO^+ lines (J=1-0) toward 4 nearby dark cloud cores, TMC-1, L1512, L1544, and L63, along with observations of the DNC and HN^13C lines (J=2-1) toward selected positions. By use of statistical equilibrium calculations based on the LVG model, the H_2 densities are derived to be (1.4-5.5)*10^5 cm^-3, and the [DNC]/[HN^13C] ratios are derived to be 1.25-5.44 with a typical uncertainty by a factor of 2. The observed [DNC]/[HNC] ratios range from 0.02 to 0.09, assuming the [^12C]/[^13C] ratio of 60. Distributions of DNC and HN^13C are generally similar to each other, whereas the distribution of H^13CO^+ is more extended than those of DNC and HN^13C, indicating that they reside in an inner part of the cores than HCO^+. The [DNC]/[HN^13C] ratio is rather constant within each core, although a small systematic gradients are observed in TMC-1 and L63. Particularly, no such systematic gradient is found in L1512 and L1544, where a significant effect of depletion of molecules is reported toward the central part of the cores. This suggests that the [DNC]/[HNC] ratio would not be very sensitive to depletion factor, unlike the [DCO^+]/[HCO^+] ratio. On the other hand, the core to core variation of the [DNC]/[HNC] ratio, which range an order of magnitude, is more remarkable than the variation within each core. These results are interpreted qualitatively by a combination of three competing time-dependent processes; gas-phase deuterium fractionation, depletion of molecules onto grain surface, and dynamical evolution of a core.
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Submitted 20 May, 2003;
originally announced May 2003.
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Atomic Carbon and CO Isotope Emission in the Vicinity of DR15
Authors:
T. Oka,
S. Yamamoto,
M. Iwata,
H. Maezawa,
M. Ikeda,
T. Ito,
K. Kamegai,
T. Sakai,
Y. Sekimoto,
K. Tatematsu,
Y. Arikawa,
Y. Aso,
T. Noguchi,
S-C. Shi,
K. Miyazawa,
S. Saito,
H. Ozeki,
H. Fujiwara,
M. Ohishi,
J. Inatani
Abstract:
We present observations of the 3P1-3P0 fine structure transition of atomic carbon [CI], the J=3-2 transition of CO, as well as of the J=1-0 transitions of 13CO and C18O toward DR15, an HII region associated with two mid-infrared dark clouds (IRDCs). The 13CO and C18O J=1-0 emissions closely follow the dark patches seen in optical wavelength, showing two self-gravitating molecular cores with mass…
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We present observations of the 3P1-3P0 fine structure transition of atomic carbon [CI], the J=3-2 transition of CO, as well as of the J=1-0 transitions of 13CO and C18O toward DR15, an HII region associated with two mid-infrared dark clouds (IRDCs). The 13CO and C18O J=1-0 emissions closely follow the dark patches seen in optical wavelength, showing two self-gravitating molecular cores with masses of 2000 Msun and 900 Msun, respectively, at the positions of the catalogued IRDCs.
Our data show a rough spatial correlation between [CI] and 13CO J=1-0. Bright [CI] emission occurs in relatively cold gas behind the molecular cores, neither in highly excited gas traced by CO J=3-2 emission nor in HII region/molecular cloud interface. These results are inconsistent with those predicted by standard photodissociation region (PDR) models, suggesting an origin for interstellar atomic carbon unrelated to photodissociation processes.
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Submitted 30 May, 2001;
originally announced May 2001.
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Large-scale mapping observations of the CI(3P1-3P0) and CO(J=3-2) lines toward the Orion A molecular cloud
Authors:
Masafumi Ikeda,
Hiroyuki Maezawa,
Tetsuya Ito,
Gaku Saito,
Yutaro Sekimoto,
Satoshi Yamamoto,
Ken'ichi Tatematsu,
Yuji Arikawa,
Yoshiyuki Aso,
Takashi Noguchi,
Sheng-Cai Shi,
Keisuke Miyazawa,
Syuji Saito,
Hiroyuki Ozeki,
Hideo Fujiwara,
Masatoshi Ohishi,
Junji Inatani
Abstract:
Large scale mapping observations of the 3P1-3P0 fine structure transition of atomic carbon (CI, 492 GHz) and the J=3-2 transition of CO (346 GHz) toward the Orion A molecular cloud have been carried out with the Mt. Fuji submillimeter-wave telescope. The observations cover 9 square degrees, and include the Orion nebula M42 and the L1641 dark cloud complex. The CI emission extends over almost the…
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Large scale mapping observations of the 3P1-3P0 fine structure transition of atomic carbon (CI, 492 GHz) and the J=3-2 transition of CO (346 GHz) toward the Orion A molecular cloud have been carried out with the Mt. Fuji submillimeter-wave telescope. The observations cover 9 square degrees, and include the Orion nebula M42 and the L1641 dark cloud complex. The CI emission extends over almost the entire region of the Orion A cloud and is surprisingly similar to that of 13CO(J=1-0).The CO(J=3-2) emission shows a more featureless and extended distribution than CI.The CI/CO(J=3-2) integrated intensity ratio shows a spatial gradient running from the north (0.10) to the south (1.2) of the Orion A cloud, which we interpret as a consequence of the temperature gradient. On the other hand, the CI/13CO(J=1-0) intensity ratio shows no systematic gradient. We have found a good correlation between the CI and 13CO(J=1-0) intensities over the Orion A cloud. This result is discussed on the basis of photodissociation region models.
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Submitted 14 December, 1999;
originally announced December 1999.