Electron Antineutrino Search at the Sudbury Neutrino Observatory

Abstract

Upper limits on the v¯e flux at the Sudbury Neutrino Observatory have been set based on the v¯e charged-current reaction on deuterium. The reaction produces a positron and two neutrons in coincidence. This distinctive signature allows a search with very low background for v¯e’s from the Sun and other potential sources. Both differential and integral limits on the v¯e flux have been placed in the energy range from 4 – 14.8 MeV. For an energy-independent ve -> v¯e conversion mechanism, the integral limit on the flux of solar v¯e’s in the energy range from 4 – 14.8 MeV is found to be Φv¯e ≤ 3.4 × 104cm−2s−1 (90% C.L.), which corresponds to 0.81% of the standard solar model 8B e flux of 5.05 × 106cm−2s−1, and is consistent with the more sensitive limit from KamLAND in the 8.3 – 14.8 MeV range of 3.7×102cm−2s−1 (90% C.L.). In the energy range from 4 – 8 MeV, a search for v¯e’s is conducted using coincidences in which only the two neutrons are detected. Assuming a v¯e spectrum for the neutron induced fission of naturally occurring elements, a flux limit of Φv¯e 2.0 × 106cm−2s−1 (90% C.L.) is obtained.