I'm doing neutrino physics in most of my time. Globe trotter after retirement, was in Brazil for longer than 3 yeas, was in Ecuador to construct Physics Department in a new university. I'm in Virginia US now.
We study visible neutrino decay at the reactor neutrino experiments KamLAND and, JUNO. Assuming t... more We study visible neutrino decay at the reactor neutrino experiments KamLAND and, JUNO. Assuming the Majoron model of neutrino decay, we obtain constraints on the couplings between Majoron and neutrino as well as on the lifetime/mass of the most massive neutrino state i.e., $$\tau _{3} / m_{3}$$ τ 3 / m 3 or $$\tau _{2} / m_{2}$$ τ 2 / m 2 , respectively, for the normal or the inverted mass orderings. We obtain the constraints on the lifetime $$\tau _{2} / m_{2} \ge 1.4 \times 10^{-9}~{\mathrm{s/eV}}$$ τ 2 / m 2 ≥ 1.4 × 10 - 9 s / eV in the inverted mass ordering for both KamLAND and JUNO at 90% CL. In the normal ordering in which the bound can be obtained for JUNO only, the constraint is milder than the inverted ordering case, $$\tau _{3} / m_{3} \ge 1.0 \times 10^{-10}$$ τ 3 / m 3 ≥ 1.0 × 10 - 10 s/eV at 90% CL. We find that the dependence of lightest neutrino mass ($$=m_{{{\mathrm{lightest}}}}$$ = m lightest ), $$m_1 (m_3)$$ m 1 ( m 3 ) for the normal (inverted) mass ordering, on...
We discuss physics of the three neutrino flavor transformation with non-unitary mixing matrix, wi... more We discuss physics of the three neutrino flavor transformation with non-unitary mixing matrix, with particular attention to the correlation between the νSM- and the α parameters which represent effect of unitarity violating (UV) new physics. Toward the goal, a new perturbative framework is created to illuminate the effect of non-unitarity in region of the solar-scale enhanced oscillations. We refute the skepticism about the physical reality of the νSM CP δ - α parameter phase correlation by analysis with the SOL convention of UMNS in which $$e^{ \pm i \delta}$$ is attached to s12. Then, a comparative study between the solar- and atmospheric-scale oscillation regions allowed by the framework reveals a dynamical δ- (blobs of the α parameters) correlation in the solar oscillation region, in sharp contrast to the “chiral” type phase correlation $$[e^{- i \delta } \bar{\alpha}_{\mu e}, e^{ - i \delta} \bar{\alpha}_{\tau e}, \bar{\alpha}_{\tau \mu}]$$ in the PDG convention seen in the atm...
We formulate a perturbative framework for the flavor transformation of the standard active three ... more We formulate a perturbative framework for the flavor transformation of the standard active three neutrinos but with a non-unitary flavor mixing matrix, a system which may be relevant for the leptonic unitarity test. We use the $\alpha$ parametrization of the non-unitary matrix and take its elements $\alpha_{\beta \gamma}$ ($\beta,\gamma = e,\mu,\tau$) and the ratio $\epsilon \simeq \Delta m^2_{21} / \Delta m^2_{31}$ as the small expansion parameters. Two qualitatively new features that hold in all the oscillation channels are uncovered in the probability formula obtained to first order in the expansion: (1) The phases of the complex $\alpha$ elements always come into the observable in the particular combination with the $\nu$SM CP phase $\delta$ in the form $[e^{- i \delta } \bar{\alpha}_{\mu e}, ~e^{ - i \delta} \bar{\alpha}_{\tau e}, ~\bar{\alpha}_{\tau \mu}]$ under the Particle Data Group convention of a unitary $\nu$SM mixing matrix. (2) The diagonal $\alpha$ parameters appear i...
We introduce "CP trajectory diagram in bi-probability space" as a powerful tool for pictorial rep... more We introduce "CP trajectory diagram in bi-probability space" as a powerful tool for pictorial representation of the genuine CP and the matter effects in neutrino oscillations. Existence of the correlated ambiguity in a determination of CP violating phase \delta and the sign of \Delta m^2_{13} is uncovered. Principles of tuning beam energy for a given baseline distance are proposed to resolve the ambiguity and to maximize the CP-odd effect. We finally point out, quite contrary to what is usually believed, that the ambiguity may be resolved with 50 % chance in the super-JHF experiment despite its relatively short baseline of 300 km.
We study visible neutrino decay at the reactor neutrino experiments KamLAND and, JUNO. Assuming t... more We study visible neutrino decay at the reactor neutrino experiments KamLAND and, JUNO. Assuming the Majoron model of neutrino decay, we obtain constraints on the couplings between Majoron and neutrino as well as on the lifetime/mass of the most massive neutrino state i.e., $$\tau _{3} / m_{3}$$ τ 3 / m 3 or $$\tau _{2} / m_{2}$$ τ 2 / m 2 , respectively, for the normal or the inverted mass orderings. We obtain the constraints on the lifetime $$\tau _{2} / m_{2} \ge 1.4 \times 10^{-9}~{\mathrm{s/eV}}$$ τ 2 / m 2 ≥ 1.4 × 10 - 9 s / eV in the inverted mass ordering for both KamLAND and JUNO at 90% CL. In the normal ordering in which the bound can be obtained for JUNO only, the constraint is milder than the inverted ordering case, $$\tau _{3} / m_{3} \ge 1.0 \times 10^{-10}$$ τ 3 / m 3 ≥ 1.0 × 10 - 10 s/eV at 90% CL. We find that the dependence of lightest neutrino mass ($$=m_{{{\mathrm{lightest}}}}$$ = m lightest ), $$m_1 (m_3)$$ m 1 ( m 3 ) for the normal (inverted) mass ordering, on...
We discuss physics of the three neutrino flavor transformation with non-unitary mixing matrix, wi... more We discuss physics of the three neutrino flavor transformation with non-unitary mixing matrix, with particular attention to the correlation between the νSM- and the α parameters which represent effect of unitarity violating (UV) new physics. Toward the goal, a new perturbative framework is created to illuminate the effect of non-unitarity in region of the solar-scale enhanced oscillations. We refute the skepticism about the physical reality of the νSM CP δ - α parameter phase correlation by analysis with the SOL convention of UMNS in which $$e^{ \pm i \delta}$$ is attached to s12. Then, a comparative study between the solar- and atmospheric-scale oscillation regions allowed by the framework reveals a dynamical δ- (blobs of the α parameters) correlation in the solar oscillation region, in sharp contrast to the “chiral” type phase correlation $$[e^{- i \delta } \bar{\alpha}_{\mu e}, e^{ - i \delta} \bar{\alpha}_{\tau e}, \bar{\alpha}_{\tau \mu}]$$ in the PDG convention seen in the atm...
We formulate a perturbative framework for the flavor transformation of the standard active three ... more We formulate a perturbative framework for the flavor transformation of the standard active three neutrinos but with a non-unitary flavor mixing matrix, a system which may be relevant for the leptonic unitarity test. We use the $\alpha$ parametrization of the non-unitary matrix and take its elements $\alpha_{\beta \gamma}$ ($\beta,\gamma = e,\mu,\tau$) and the ratio $\epsilon \simeq \Delta m^2_{21} / \Delta m^2_{31}$ as the small expansion parameters. Two qualitatively new features that hold in all the oscillation channels are uncovered in the probability formula obtained to first order in the expansion: (1) The phases of the complex $\alpha$ elements always come into the observable in the particular combination with the $\nu$SM CP phase $\delta$ in the form $[e^{- i \delta } \bar{\alpha}_{\mu e}, ~e^{ - i \delta} \bar{\alpha}_{\tau e}, ~\bar{\alpha}_{\tau \mu}]$ under the Particle Data Group convention of a unitary $\nu$SM mixing matrix. (2) The diagonal $\alpha$ parameters appear i...
We introduce "CP trajectory diagram in bi-probability space" as a powerful tool for pictorial rep... more We introduce "CP trajectory diagram in bi-probability space" as a powerful tool for pictorial representation of the genuine CP and the matter effects in neutrino oscillations. Existence of the correlated ambiguity in a determination of CP violating phase \delta and the sign of \Delta m^2_{13} is uncovered. Principles of tuning beam energy for a given baseline distance are proposed to resolve the ambiguity and to maximize the CP-odd effect. We finally point out, quite contrary to what is usually believed, that the ambiguity may be resolved with 50 % chance in the super-JHF experiment despite its relatively short baseline of 300 km.
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