Search for Supernova Neutrinos with the JUNO detector

Observation of supernovae through their neutrino emission is a major fundamental field to understand both supernova dynamics and neutrino physical properties. JUNO is a 35 kiloton scintillator detector, planned to start its activity in about 4 years in the Jiangmen region, China. It is based on an acrylic vessel with a diameter of 35 meters filled with an ultra-pure liquid scintillator and rigged with ~ 18000 large (20”) and ~ 35000 small (3”) photomultipliers. The primary aim of the experiment is to determine the neutrino mass hierarchy with a precise measurement of the oscillation of neutrinos produced in two nuclear reactors located at ~ 50 km from the detector. In this thesis we analyze the detector structure and the proposed readout strategies and data acquisition architecture in order to evaluate the performance in the case of a supernova burst having a much higher event rate with respect to the nuclear reactor flux. Taking advantage of an existing Monte Carlo software developed by the JUNO collaboration for the simulation of the supernova neutrino flux at the detector, in this thesis we build a complete framework implementing a GEANT4 simulation of JUNO that is used to simulate the detector response to the supernova neutrino interactions. By means of this framework we characterize the response of the JUNO detector to a neutrino SN burst in terms of detection rate and neutrino energy reconstruction. In particular we study the behaviour of the 3” PMT system which thanks to the faster readout is the most suitable for the acquisition of an high-rate event as a supernova burst. Using simulated data we evaluate a possible analysis strategy to reconstruct the SN neutrinos flux and its time distribution. The efficiencies of different SN neutrino detection channels are evaluated and presented in the thesis. Where existing data from SN neutrino consists only of the 24 neutrino events detected from SN1987A, the detection in JUNO of a supernova from a progenitor at 10 kpc will yield ~ 5000 inverse beta decay interaction from electron antineutrinos, plus several hundreds on other CC and NC interaction channels from all neutrino species