27 research outputs found
Search for astrophysical electron antineutrinos in Super-Kamiokande with 0.01wt% gadolinium-loaded water
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 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 () owing
to the enhanced neutron tagging
Performance of SK-Gd’s upgraded real-time supernova monitoring system
Among multimessenger 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. In 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 has been upgraded. SK_SN Notice, a warning system that works together with this monitoring system, was released on 2021 December 13, and is available through GCN Notices. 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° to 7° 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
Performance of SK-Gd's upgraded real-time supernova monitoring system
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∘ 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
Search for proton decay via <math display="inline"><mi>p</mi><mo stretchy="false">→</mo><msup><mi>μ</mi><mo>+</mo></msup><msup><mi>K</mi><mn>0</mn></msup></math> in 0.37 megaton-years exposure of Super-Kamiokande
International audienceWe searched for proton decay via p→μ+K0 in 0.37 Mton·years of data collected between 1996 and 2018 from the Super-Kamiokande water Cherenkov experiment. The selection criteria were defined separately for KS0 and KL0 channels. No significant event excess has been observed. As a result of this analysis, which extends the previous search by an additional 0.2 Mton·years of exposure and uses an improved event reconstruction, we set a lower limit of 3.6×1033 years on the proton lifetime
Search for proton decay via in 0.37 megaton-years exposure of Super-Kamiokande
We searched for proton decay via in 0.37 Mtonyears of data collected between 1996 and 2018 from the Super-Kamiokande water Cherenkov experiment. The selection criteria were defined separately for and channels. No significant event excess has been observed. As a result of this analysis, which extends the previous search by an additional 0.2 Mtonyears of exposure and uses an improved event reconstruction, we set a lower limit of years on the proton lifetime