Topical Experimental Studies On Supernova Neutrino Detection

Core-collapse supernovae are the most energetic astrophysical events since the Big Bang.About 99%of the emitted energy is released by a tremendous number of neutrinos and antineutrinos of all flavors,with an average energy of 10-20 MeV.These neutrinos will play an irreplaceable role in studying the intrinsic properties of neutrinos and new phenomena beyond the standard model of particle physics.They also carry valuable information on supernova dynamics as well as stellar evolution.Hence,the detection of supernova neutrinos is an important interdisciplinary field of particle physics,astrophysics,nuclear physics,and cosmology.To date,the experimental studies on supernova neutrinos are not only for supernova burst neutrinos,but also for supernova relic neutrinos which are diffuse thoughout the universe from all the past supernova explosions.For the on-going Daya Bay reactor neutrino experiment and the proposed Jinping neutrino experiment,this thesis presents three experimental studies on supernova neu-trinos,mainly using the inverse beta decay?IBD?interactions of supernova electron antineutrinos.1)The design,implementation,testing,and operation of a supernova online trigger system were accomplished at Daya Bay,which has a unique feature of multiple detectors deployed at separate sites.Using IBD events from the multiple detectors,an effective algorithm was developed to let the trigger system to be the most prompt in the world and with the lowest energy threshold,and fully sensitive to core-collapse supernovae within20 kpc.This trigger system was installed at Daya Bay in August 2013 and officially integrated into the worldwide Supernova Early Warning System in November 2014.2)Supernova neutrino bursts were searched for using the Daya Bay data set acquired from 2011 December to 2013 November.The interaction of neutrino neutral-current excitation of¹²C was exploited for supernova neutrino detection,making best use of the target mass of the Daya Bay detectors.This search,with an energy threshold of 10 MeV,retains a 100%detection probability of core-collapse supernovae out to 25 kpc,which is comparable to that for the world-leading experiments.Combined with the currently-running online trigger system,the 90%C.L.upper limit on the rate of core-collapse supernovae is found to be 0.5/year.In addition,a search with a lower energy threshold of 0.7 MeV aims at a model-independent search for supernova neutrino bursts and allows a detection of the full energy spectrum of supernova neutrinos.Two candidates were identified and attributed to the background based on their occurrence rate and energy spectrum.No coincident astronomical observations of supernovae were found.Two exotic searches for coincident neutrino events with SN2014J and GW150914 were also performed.3)A computational study was carried out for the proposed Jinping neutrino experi-ment which would have the world's deepest overburden of rock and a long distance from nuclear power plants,thus providing an ultra-low cosmic-ray muon-induced background and reactor neutrino background.As a result,a kiloton-scale neutrino detector is promis-ing to make the first discovery of supernova relic neutrinos,the backgrounds for which mainly originate from the atmospheric neutrinos.The potential sensitivity is found to be comparable to that of other proposed 10-kiloton-scale typical liquid scintillator detectors or water Cherenkov detectors?as is the sensitivity to supernova neutrino bursts?.With a data set of 20 kt-year,the supernova relic neutrinos predicted by the HBD?Horiuchi,Beacom,and Dwek 2009?model can be discovered at a 99.95%confidence level at Jinping.