Systematic limits on sin 22θ13 in neutrino oscillation experiments with multireactors

Sensitivities to sin 22θ13 without statistical errors ("systematic limit") are investigated in neutrino oscillation experiments with multiple reactors. Using an analytical approach, we show that the systematic limit on sin 22θ13 is dominated by the uncorrelated systematic error σu of the detector. Even in an experiment with multidetectors and multireactors, it turns out that most of the systematic errors including the one due to the nature of multiple sources is canceled as in the case with a single reactor plus two detectors, if the near detectors are placed suitably. The case of the KASKA plan (7 reactors and 3 detectors) is investigated in detail, and it is explicitly shown that it does not suffer from the extra uncertainty due to multiple reactors.