Avoiding the uncertainty from correlation between |Delta m_{31}^2| and CP phase delta in nu_mu --> nu_mu long baseline experiments

We introduce a new index I_{Delta m_{31}^2} to find where is the better setup of the baseline length and energy to avoid as well as possible the uncertainty from the correlation between Delta m_{31}^2 and cos(delta) in nu_mu --> nu_mu long baseline experiments.Comment: 6 pages, 9 figure

The F/D Ratios of Spin-flip Baryon Vertex in 1/N_c Expansion

We calculate the $F/D$ ratios of spin 1/2 baryon vertex for both the non-relativistic quark model and the chiral soliton model with arbitrary number of color degrees of freedom $N_c$ and examine the results in terms of the consistency condition approach for the baryon vertices recently developed by Dashen, Jenkins and Manohar from the viewpoint of QCD. We show that the $1/N_c$ corrections have two different origins, i.e. one is from the baryon states or baryon wave functions and the other from the vertex operators. Although in the limit of $N_c \to \infty$ the $F/D$ tends to 1/3 in all models, the $1/N_c$ expansion of $F/D$ ratio does not converge for $N_c=3$ in the chiral soliton model in contrast to the non-relativistic quark model.Comment: 14 pages, Latex, 1 figur

Resonant Spin-Flavor Conversion of Supernova Neutrinos: Dependence on Electron Mole Fraction

Detailed dependence of resonant spin-flavor (RSF) conversion of supernova neutrinos on electron mole fraction Ye is investigated. Supernova explosion forms a hot-bubble and neutrino-driven wind region of which electron mole fraction exceeds 0.5 in several seconds after the core collapse. When a higher resonance of the RSF conversion is located in the innermost region, flavor change of the neutrinos strongly depends on the sign of 1-2Ye. At an adiabatic high RSF resonance the flavor conversion of bar{nu}_e -> nu_{mu,tau} occurs in Ye 0.5 and inverted mass hierarchy. In other cases of Ye values and mass hierarchies, the conversion of nu_e -> bar{nu}_{mu,tau} occurs. The final bar{nu}_e spectrum is evaluated in the cases of Ye 0.5 taking account of the RSF conversion. Based on the obtained result, time variation of the event number ratios of low bar{nu}_e energy to high bar{nu}_e energy is discussed. In normal mass hierarchy, an enhancement of the event ratio should be seen in the period when the electron fraction in the innermost region exceeds 0.5. In inverted mass hierarchy, on the other hand, a dip of the event ratio should be observed. Therefore, the time variation of the event number ratio is useful to investigate the effect of the RSF conversion.Comment: 16 pages, 33 figures, accepted for publication in Physical Review

Measuring the Leptonic CP Phase in νμ→νμ\nu_{\mu} \to \nu_{\mu} Oscillations

In $\nu_{\mu} \to \nu_{\mu}$ oscillations, we find that the effect of the CP phase $\delta$ becomes large in the region $E2000$ km. In this region, the change of the probability in this channel reaches about 0.4 due to the CP phase effect beyond our expectation in the case of large 1-3 mixing angle. Furthermore, the CP phase effect have almost same sign over the region $E>0.5$ GeV so that one may find the signal of CP violation by measuring the total rate only. As an example, we use an experimental setup and demonstrate that the allowed region is limited to one by combined analysis of $\nu_e$ and $\nu_{\mu}$ events although there remain three allowed regions by the analysis of $\nu_e$ events alone.Comment: 7 pages, 8 figures, version to appear in PL

New Index of CP Phase Effect and θ13\theta_{13} Screening in Long Baseline Neutrino Experiments

We introduce a new index of the leptonic CP phase dependence $I_{\rm CP}$ and derive the maximal condition for this index in a simple and general form. $I_{\rm CP}\simeq 100$ may be realized even in the JPARC experiment. In the case that the 1-3 mixing angle can be observed in the next generation reactor experiments, namely $\sin^2 2\theta_{13}>0.01$, and nevertheless $\nu_e$ appearance signal cannot be observed in the JPARC experiment, we conclude that the CP phase $\delta$ becomes a value around $135^{\circ}$ $(45^{\circ})$ for $\Delta m^2_{31}>0$ $(\Delta m^2_{31}<0)$ without depending the uncertainties of solar and atmospheric parameters.Comment: 7 pages, 7 figures, version to appear in PL

Supernova Neutrino Nucleosynthesis of Light Elements with Neutrino Oscillations

Light element synthesis in supernovae through neutrino-nucleus interactions, i.e., the ν-process, is affected by neutrino oscillations in the supernova environment. There is a resonance of 13-mixing in the O/C layer, which increases the rates of charged-current ν-process reactions in the outer He-rich layer. The yields of 7Li and 11B increase by about a factor of 1.9 and 1.3, respectively, for a normal mass hierarchy and an adiabatic 13-mixing resonance, compared to those without neutrino oscillations. In the case of an inverted mass hierarchy and a non-adiabatic 13-mixing resonance, the increase in the 7Li and 11B yields is much smaller. Observations of the 7Li/11B ratio in stars showing signs of supernova enrichment could thus provide a unique test of neutrino oscillations and constrain their parameters and the mass hierarchy