Gamma-Ray Echo as a Probe of Supernova Neutrino Emission Anisotropy and Long-Baseline Effects
During a core-collapse supernova (CCSN), the emitted electron antineutrino ($\bar{\nu}_e$) burst initiates inverse beta decay (IBD) in the outer hydrogen layer of the stellar envelope. This leads to the production of a characteristic 511 keV photon signal, termed the Gamma-Ray Echo. The same neutrino burst, when detect...