CHOOZ

Chooz (French: ) was a short baseline neutrino oscillation experiment in Chooz, France. Its major result was setting limits on the neutrino oscillation parameters responsible for changing electron neutrinos into other neutrinos. Specifically, it found that sin2(2θ13) < 0.17 for large δm2 and δm2 > 8×10−4 eV2 for maximal mixing. Results were published in 1999. Chooz (French: ) was a short baseline neutrino oscillation experiment in Chooz, France. Its major result was setting limits on the neutrino oscillation parameters responsible for changing electron neutrinos into other neutrinos. Specifically, it found that sin2(2θ13) < 0.17 for large δm2 and δm2 > 8×10−4 eV2 for maximal mixing. Results were published in 1999. The Double Chooz experiment continues to take data using the same lab space. Chooz used neutrinos from two pressurized water reactors, which provide a >99.999% νe source. The average neutrino energy was approximately 3 MeV, and the detector was roughly 1000 m from the reactor. The intensity was measured using both the heat balance and neutron output of the reactor, and was known to better than 2%. Detailed modeling of the reactor cores was used to predict both the intensity and energy spectrum of the neutrinos as a function of time. Neutrinos were observed via the inverse beta decay reaction (p + νe → n + e+). The Chooz detector was underground, with a 300 meter water equivalent overburden to reduce cosmic ray backgrounds. The detector itself was a cylinder 5.5 m in diameter and 5.5 m tall. The detector was composed of three regions. The innermost region (region I) contained 5 tons of scintillator doped with gadolinium in a Plexiglas container. The gadolinium quickly captured the neutrons produced in the inverse beta decay. The second region (region II) contained 17 tons of undoped scintillator to capture the electromagnetic energy from the inverse beta decay (≈99%) and the photons from the neutron capture in the Gd (>95%). The outer surface of region II contained 192 inward facing photomultiplier tubes (PMT) held in an opaque plastic structure.