SEARCH FOR EXTRATERRESTRIAL ANTINEUTRINO SOURCES WITH THE KamLAND DETECTOR

Abstract

We present the results of a search for extraterrestrial electron antineutrinos ( e 's) in the energy range 8.3 MeV < E e < 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 8 B solar e 's converting into e 's at 5.3 10 -5 (90% CL), if we assume an undistorted e shape. This limit corresponds to a solar e flux of 93 cm -2 s -1 or an event rate of 1.6 events (kton-year) -1 above the energy threshold (E e 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.