How will Double Chooz Measure θ13?


The Double Chooz site. The near detector is at the bottom of the picture, approximately
400 m away from reactor cores and 40 m underground and the far detector is in the left
part of the picture, approximately 1.1 km away and 110 m underground. The (electron anti)
neutrino source are west reactor and east nuclear reactor. All electron anti-neutrinos from
nuclear reactor cores reach near detector as electron anti-neutrino type, while some of the
anti-neutrinos have enough time to convert to other types (muon and tau anti-neutrino)
before reaching the far detector.

  • Double Chooz uses two detectors of electron anti-neutrinos located at different distances away from a pair of nuclear reactors that serve as anti-neutrino sources.
  • Both near and far detector will measure the number and energy of neutrinos coming from the nuclear reactor cores.
  • Near detector is close enough (400 m) to the nuclear reactors core that all neutrinos arrive in there original flavor (electron anti-neutrino).
  • Far detector is 1.1 km away from the nuclear reactors and depending on the size of θ13 part of neutrinos will change their type into muon or tau anti-neutrino and will therefore not be detected.  (Detectors can only detect electron anti-neutrinos.)
  • Difference between the number of neutrinos detected by the near and the far detector will be equal to the fraction of electron anti-neutrinos that changed their flavor into muon or tau anti-neutrino before reaching the far detector.
  • Conversion electron anti-neutrino rate into a different neutrino flavor directly depends upon the size of θ13
  • The utilization of two identical detectors will ensure an accurate measurement of θ13