2018 Fiscal Year Annual Research Report
Studying supernova explosions via their neutrino emissions
| Project Area | Gravitational wave physics and astronomy: Genesis |
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| Project/Area Number |
17H06365
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| Research Institution | The University of Tokyo |
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Principal Investigator |
ヴァギンズ マーク 東京大学, カブリ数物連携宇宙研究機構, 教授 (90509902)
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| Co-Investigator(Kenkyū-buntansha) |
住吉 光介 沼津工業高等専門学校, 教養科, 教授 (30280720)
小汐 由介 岡山大学, 自然科学研究科, 准教授 (80292960)
松古 栄夫 大学共同利用機関法人高エネルギー加速器研究機構, 計算科学センター, 助教 (10373185)
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| Project Period (FY) |
2017-06-30 – 2022-03-31
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| Keywords | gravitational wave / supernova explosion / neutrino / neutron detection / hydrodynamic simulation |
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| Outline of Annual Research Achievements |
One of the primary sources of near-field gravitational waves [GW] are core collapse supernova [SN] explosion. SN neutrinos, famously observed from SN1987A, provide a unique and vital probe into the inner dynamics of these dramatic events. Released together with GW during the initial stellar collapse, neutrinos and GW are both certain to travel through any obscuring dust or gas and remain undiminished upon their arrival at Earth. Neutrinos also carry information regarding the end state of the star: for explosions within our galaxy, collapses into neutron stars or black holes, the eventual sources of far-field GW, can be differentiated via observations of neutrino emissions.
During FY2018, we began upgrading the existing Super-Kamiokande [SK] detector to be an advanced-technology, gadolinium-loaded SN neutrino detector. This was the first time SK was drained and serviced since 2006.
There were four main tasks: 1) fix a longstanding water leak in the SK tank; 2) clean up the interior of the detector; 3) replace failed photomultiplier tubes, and; 4) install additional piping for better circulation of Gd-loaded water.
On the theory side, SN simulations by 6D Boltzmann equation were performed on the K-computer to clarify the effects of SN core rotation in neutrino emission and transport. Moreover, the properties of SN dynamics and neutrino bursts for different progenitors and sets of the equation of state were explored as an evaluation of uncertainty in neutrino signals. We developed numerical codes for supernovae suitable for use on GPU systems.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
Our ultimate goal is to make theory and experiment work together so we will be ready to make the best possible observations of the next galactic explosion and maximize our extraction of information on the explosion mechanism, progenitor, and nuclear physics ingredients.
The SK refurbishment was a major experimental effort, involving over 3000 person-days of in-tank work during FY2018. All goals were achieved on time. The refilled, operating detector is now nearly ready for the addition of gadolinium and the greatly enhanced supernova neutrino sensitivity it will bring.
We have established a strong collaboration to provide supernova neutrino light curves by combining both theoretical and experimental members. These joint SK/theory neutrino light curve meetings have been very fruitful and enjoyable for both sides. We constructed a procedure to provide the expected neutrino event numbers at SK from the supernova numerical simulations and provided standard properties of supernova neutrino light curves for a set of supernova simulations.
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| Strategy for Future Research Activity |
Now that the Super-Kamiokande detector has been refurbished and refilled with ultrapure water, a new Gd-capable selective water filtration system will be commissioned and its ability to maintain the clarity of SK's pure water will be demonstrated. After that, the detector will be ready for enrichment with gadolinium.
On the theory side, more systematic analysis of supernova dynamics and neutrino signals will be made by performing additional simulations by 6D Boltzmann equation to extract the information of supernova neutrino bursts with reduction of the uncertainties due to progenitors and nuclear physics. Through the collaboration of theory and experiments, systematic studies of the neutrino light curves for various supernovae will be made to determine an optimal procedure to extract as much supernova information as possible from future burst events.
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