Search For Neutrinos Associated With Gravitational-waves Or Gamma-ray Bursts At Daya Bay

Neutrinos associated with gravitational waves(GW)or gamma-ray bursts(GRB)are produced in the universe during the coalescence of compact binaries or the collapse of massive stars and have characteristics of short bursts.So far,theories are unclear about the physical processes that occur inside such celestial events.Neutrinos travel through space,interacting so weakly with matter that they act as messengers,carrying the most primitive information from the interior of celestial point sources to detectors on Earth.In the era of multi-messengers,combined observations of neutrinos,gravitational waves,and gamma-ray bursts are crucial to understanding the dynamics of these celestial processes and the universe's evolution.This dissertation used about 340 tons of liquid scintillators in 8 electron anti-neutrino detectors in Daya Bay to search for correlated signals.The main work and innovations are as follows:·The energy differential cross-section of the inverse-beta-decay reaction for electronanti-neutrinos was studied by analyzing the deviation of cross-section calculationswith increasing energy.The recoil neutron's influence on positron energy mea-surement was under discussion and yielding a modified formula to take effect intoaccount.We performed simulation studies to compare the different databases forthe thermalization,capture the above reaction's cross-section of the delayed neu-tron,and estimated the effect on detection efficiency.·We searched for electron anti-neutrino events with a prompt positron and delayedneutron capture signals associated with the complete gravitational wave events-GW150914,GW151012,GW151226,GW170104,GW170608,GW170814,andGW170817-caused by compact binaries'mergers in the Daya Bay experiment.Ac-cording to different motivations,we applied multiple search time windows,±10 s,±500 s,and±1000 s.We found that all were consistent with the background leveland accordingly derived the corresponding upper limit of neutrino fluence.Underthe monochromatic energy spectra's assumption,the upper limit of neutrino fluenceof 5 Me V-90 Me V at 90%confidence interval is(1.12-2.28)×10¹¹cm^-2to 1.0×10⁸cm^-2.Under the assumption of the Fermi-Dirac energy spectrum,the upperlimit of neutrino fluence in(1.8 Me V,100 Me V)energy region and different timewindows is(4.2-5.5)×10⁹cm^-2.·We analyzed a total of 2225 events of GRBs occurring from December 2011 to March 2019.The searching time window of correlated neutrino signal includes±500 s,±1000 s,and a dynamic time window determined by different GRBs du-ration and redshift.The results show that the number of neutrino signals did not exceed the number of backgrounds.The upper limit of fluence at the Daya Bay experiment was between 0.08×10⁷cm^-2and 2.03×10¹⁰cm^-2at the 90%con-fidence level for the monochromatic energy spectra hypothesis and(2.08-10.8)×10⁷cm^-2for the Fermi-Dirac energy spectrum assumption.These limits are the latest upper bound results of GRB associated neutrino fluence in the world.