SEARCH FOR EXTRATERRESTRIAL ANTINEUTRINO SOURCES WITH THE KamLAND DETECTOR.

We present the results of a search for extraterrestrial electron antineutrinos (퐯̄e's) in the energy range 8.3 MeV < E퐯̄e < 31.8 MeV using the KamLAND detector. In an exposure of 4.53 kton-year, we identify 25 candidate events. All of the candidate events can be attributed to background, most importantly neutral current atmospheric neutrino interactions, setting an upper limit on the probability of 8B solar ve's converting into 퐯̄e's at 5.3 x 10-5 (90% CL), if we assume an undistorted 퐯̄e shape. This limit corresponds to a solar 퐯̄e flux of 93 cm-2 s-1 or an event rate of 1.6 events (kton-year)-1 above the energy threshold (E퐯̄e ≳ 8.3 MeV). The present data also allows us to set more stringent limits on the diffuse supernova neutrino flux and on the annihilation rates for light dark matter particles. [ABSTRACT FROM AUTHOR]