Exploiting the directional sensitivity of the double Chooz near detector

Abstract

In scintillator detectors, the forward displacement of the neutron in the reaction {nu}{sub e}+p{yields}e{sup +}+n provides neutrino directional information as demonstrated by the CHOOZ reactor experiment with 2500 events. The near detector of the forthcoming Double Chooz experiment will collect 1.6x10{sup 5} events per year, enough to determine the average neutrino direction with a 1{sigma} half-cone aperture of 2.3 deg. in one year. It is more difficult to separate the two Chooz reactors that are viewed at a separation angle {phi}=30 deg. If their strengths are known and approximately equal, the azimuthal location of each reactor is obtained with {+-}6 deg. (1{sigma}) and the probability of confusing them with a single source is less than 11%. Five-year's data reduce this 'confusion probability' to less than 0.3%, i.e., a 3{sigma} separation is possible. All of these numbers improve rapidly with increasing angular separation of the sources. For a setup with {phi}=90 deg. and one-year's data, the azimuthal 1{sigma} uncertainty for each source decreases to {+-}3.2 deg. Of course, for Double Chooz the two reactor locations are known, allowing one instead to measure their individual one-year integrated power output to {+-}11% (1{sigma}), and their five-year integrated output to {+-}4.8% (1{sigma})