Is CP Violation Observable in Long Baseline Neutrino Oscillation Experiments ?

We have studied the direct measurements of CP violation in the neutrino oscillations: the difference of the transition probabilities between CP -conjugate channels in the long baseline accelerator experiments. In those experiments, the CP violating effect is not suppressed if the highest neutrino mass scale is taken to be 1 ∼ 10eV, which is appropriate for the cosmological hot dark matter. The upper bounds of CP violation have been caluculated for three cases, in which mixings are constrained by the recent short baseline ones. The caluculated upper bounds are larger than 10, which will be observable in the long baseline accelerator experiments. The new reactor disappearance experiments will provide severer bounds of CP violation in the near future. E-mail address: [email protected]