DETERMINING NEUTRINO PARAMETERS FROM FUTURE LONG-BASELINE OSCILLATION EXPERIMENTS

Assuming three flavors of neutrinos, ve, v^ and uT and the standard parameterization of the MNS mixing matrix, neutrino oscillation parameters are currently constrained as \ Am^ ~ 7 x 1CT5 eV2, sin2 2#i2 ^ 0.85 from solar neutrino observations and the KamLAND experiment, Am23 ~ 2.5 x 10~3 eV2, sin22023 — 1-0 from atmospheric neutrinos and K2K experiment, sin2 29\z ^ 0.2 from CHOOZ experiment. Next step is to answer (1) How small is #13?, (2) What is the sign of Am23? and (3) What is the value of CP/T violating phase 51 The first stage of the next generation long-baseline neutrino oscillation experiments with superbeams 2 will be devoted to the precise measurement of Am^ and sin2 2023 and discovery of non-zero #13. If #13 is turned out to be non-zero, we can eventually study the effect of CP violation and neutrino mass hierarchy by oscillation experiments. In this short contribution, we illustrate a possible strategy to determine oscillation parameters using the bi-probability plots which are useful for qualitative understanding. Due to the tight space limitation, we will show only a few illustrative plots and short descriptions about them and refer Refs. 6>7 and the references therein for more detail. We have introduced and studied bi-probability plots in Refs.3'4'5'6'7'8. In Fig. 1, we show some examples of such plots for JHF and NuMI oscillation experiments where allowed region in the bi-probability planes are shown with represented ellipses with fixed values of #13. From these plots we can conclude that if the CP phase is close to 3TT/2 (TT/2) for Aro23 > 0 (Ara23 < 0) we have a good