### Browsing by Author "Minakata, Hisakazu"

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- Constraining visible neutrino decay at KamLAND and JUNOPorto-Silva, Yago P.; Prakash, Suprabh; Peres, O. L. G.; Nunokawa, Hiroshi; Minakata, Hisakazu (2020-10-29)
Show 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) or tau(2)/m(2), respectively, for the normal or the inverted mass orderings. We obtain the constraints on the lifetime tau(2)/m(2)>= 1.4x10(-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) >= 1.0 x 10(-1)0 s/eV at 90% CL. We find that the dependence of lightest neutrino mass (= m(lightest)), m(1)(m(3)) for the normal (inverted) mass ordering, on the constraints for the different types of couplings (scalar or pseudo-scalar) is rather strong, but the m(lightest) dependence on the lifetime/mass bound is only modest.Show more - Interference between the atmospheric and solar oscillation amplitudesHuber, Patrick; Minakata, Hisakazu; Pestes, Rebekah (2020-05-12)
Show more We propose to detect the interference effect between the atmospheric-scale and solar-scale waves of neutrino oscillation, one of the key consequences of the three-generation structure of leptons. In vacuum, we show that there is a natural and general way of decomposing the oscillation amplitude into these two oscillation modes. The nature of the interference is cleanest in the (nu) over bar (e) disappearance channel, since it is free from the CP phase delta. We find that the upcoming JUNO experiment offers an ideal setting to observe this interference with more than 4 sigma significance, even under conservative assumptions about the systematic uncertainties. Finally, we discuss the relationship between the mass-ordering resolution and the interference effect.Show more - Measuring tau neutrino appearance probability via unitarityMartinez-Soler, Ivan; Minakata, Hisakazu (American Physical Society, 2021-11-16)
Show more We propose a unitarity method for determining tau neutrino appearance probability P(nu mu -> nu tau) in longbaseline (LBL) accelerator experiments and atmospheric neutrino observations. When simultaneous in situ measurements of P(nu mu -> nu mu) and P(nu mu -> nu e) proceed, as is typical in the LBL experiments, one can use unitarity to "measure" P(nu mu -> nu tau). A theorists' toy analysis for the model-independent determination of P(nu mu -> nu mu) and P(nu mu -> nu e) is presented by using the NOvA data. It is shown in our analysis that less than or similar to 5% (8%) measurement of tau neutrino appearance probability in neutrino (antineutrino) mode is possible in the peak region 1.5 less than or similar to E nu less than or similar to 2.5 GeV. The nu SM-independent nature of determination of the probabilities is emphasized.Show more - Neutrino amplitude decomposition in matterMinakata, Hisakazu (2021-03-15)
Show more Observation of the interference between the atmospheric-scale and solar-scale oscillations is one of the challenging and tantalizing goals of the ongoing and upcoming neutrino experiments. An inevitable first step required for such analyses is to establish the way the oscillation S matrix can be decomposed into the atmospheric and solar waves, the procedure dubbed as the amplitude decomposition. In this paper, with the use of the perturbative framework proposed by Denton et al. (DMP), we establish the prescription for amplitude decomposition which covers the whole kinematical region of the terrestrial neutrino experiments. We analyze the limits to the atmospheric- and solar-resonance regions to argue that the dynamical two modes of the DMP decomposition can be interpreted as the matter-dressed atmospheric and solar oscillations. The expressions of the oscillation probability, which are decomposed into the noninterference and interference terms, are derived for all the relevant flavor oscillation channels. Through construction of the DMP decomposition, we reveal the nature of psi (theta(12) in matter) symmetry as due to the S matrix rephasing invariance. A new picture of the DMP perturbation theory emerged, a unified perturbative framework for neutrino oscillation in earth matter.Show more - Neutrino amplitude decomposition, S matrix rephasing invariance, and reparametrization symmetryMinakata, Hisakazu (2024-02-07)
Show more Abstract The S matrix rephasing invariance is one of the fundamental principles of quantum mechanics that originates in its probabilistic interpretation. For a given S matrix which describes neutrino oscillation, one can define the two different rephased amplitudes S αβ Reph − 1 ≡ e i λ 1 / 2 E x S αβ $$ {S}_{\alpha \beta}^{\textrm{Reph}-1}\equiv {e}^{i\left({\lambda}_1/2E\right)x}{S}_{\alpha \beta} $$ and S αβ Reph − 2 ≡ e i λ 2 / 2 E x S αβ $$ {S}_{\alpha \beta}^{\textrm{Reph}-2}\equiv {e}^{i\left({\lambda}_2/2E\right)x}{S}_{\alpha \beta} $$ , which are physically equivalent to each other, where λk/2E denotes the energy eigenvalue of the k-th mass eigenstate. We point out that the transformation of the reparametrization (Rep) symmetry obtained with “Symmetry Finder” maps S αβ Reph − 1 $$ {S}_{\alpha \beta}^{\textrm{Reph}-1} $$ to S αβ Reph − 2 $$ {S}_{\alpha \beta}^{\textrm{Reph}-2} $$ , and vice versa, providing a local and manifest realization of the S matrix rephasing invariance by the Rep symmetry of the 1–2 state exchange type. It is strongly indicative of quantum mechanical nature of the Rep symmetry. The rephasing and Rep symmetry relation, though its all-order treatment remains incomplete, is shown to imply absence of the pure 1–3 exchange symmetry in Denton et al. perturbation theory. It then triggers a study of convergence of perturbation series.Show more - Neutrino oscillations at JUNO, the Born rule, and Sorkin's triple path interferenceHuber, Patrick; Minakata, Hisakazu; Minic, Djordje; Pestes, Rebekah; Takeuchi, Tatsu (American Physical Society, 2022-06-10)
Show more We argue that neutrino oscillations at JUNO offer a unique opportunity to study Sorkin's triple path interference, which is predicted to be zero in canonical quantum mechanics by virtue of the Born rule. In particular, we compute the expected bounds on triple path interference at JUNO and demonstrate that they are comparable to those already available from electromagnetic probes. Furthermore, the neutrino probe of the Born rule is much more direct due to an intrinsic independence from any boundary conditions, whereas such dependence on boundary conditions is always present in the case of electromagnetic probes. Thus, neutrino oscillations present an ideal probe of this aspect of the foundations of quantum mechanics.Show more - Physics of parameter correlations around the solar-scale enhancement in neutrino theory with unitarity violationMartinez-Soler, Ivan; Minakata, Hisakazu (2020-11)
Show more We discuss the physics of the three neutrino flavor transformation with non-unitary mixing matrix, with particular attention to the correlation between the nu SM- and the alpha parameters which represent the effect of unitarity-violating (UV) new physics. Towards this goal, a new perturbative framework is created to illuminate the effect of non-unitarity in the region of the solar-scale enhanced oscillations. We refute the skepticism about the physical reality of the nu Standard Model CP phase delta-alpha parameter phase correlation by analysis with the SOL convention of U-MNS, in which e(+/- i delta) is attached to s(12). Then, a comparative study between the solar- and atmospheric-scale oscillation regions allowed by the framework reveals a dynamical delta-(blobs of the a parameters) correlation in the solar oscillation region, in sharp contrast to the "chiral"-type phase correlation [e(-i delta) (alpha) over bar (mu e), e(-i delta)(alpha) over bar (tau e), (alpha) over bar (tau mu)] in the Particle Data Group convention seen in the atmospheric oscillation region. An explicit perturbative calculation to the first order in the nu(mu) -> nu(e) channel allows us to decompose the UV related part of the probability into the unitary evolution part and the genuine non-unitary part. We observe that the effect of non-unitarity tends to cancel between these two parts, as well as between the different alpha(beta gamma) parameters.Show more - Symmetry Finder applied to the 1-3 mass eigenstate exchange symmetryMinakata, Hisakazu (2021-11)
Show more In a previous paper, Symmetry Finder (SF) method is proposed to find the reparametrization symmetry of the state-exchange type in neutrino oscillation in matter. It has been applied successfully to the 1-2 state exchange symmetry in the DMP perturbation theory, yielding the eight symmetries. In this paper, we apply the SF method to the atmospheric-resonance perturbation theory to uncover the 1-3 state relabeling symmetries. The pure 1-3 state symmetry takes the unique position that it is practically impossible to formulate in vacuum under the conventional choice of the flavor mixing matrix. In contrast, our SF method produces the sixteen 1-3 state exchange symmetries in matter. The relationship between the symmetries in the original (vacuum plus matter) Hamiltonian and the ones in the diagonalized system is discussed.Show more - Symmetry finder: A method for hunting symmetry in neutrino oscillationMinakata, Hisakazu (2021-10-18)
Show more Symmetry in neutrino oscillation serves for a better understanding of the physical properties of the phenomenon. We present a systematic way of finding symmetry in neutrino oscillation, which we call symmetry finder (SF). By extending the known framework in vacuum into a matter environment, we derive the SF equation, a powerful machinery for identifying symmetry in the system. After learning lessons on symmetry in the Zaglauer-Schwarzer system with matter equivalent to the vacuum symmetry, we apply the SF method to the [P. B. Denton et al., Compact perturbative expressions for neutrino oscillations in matter, J. High Energy Phys. 06 (2016) 051.] (DMP) perturbation theory to first order. We show that the method is so powerful that we uncover the eight reparametrization symmetries with the 1 <-> 2 state exchange in DMP, denoted as IA, IB,.., IVB, all new except for IA. The transformations consist of both fundamental and dynamical variables, indicating their equal importance. It is also shown that all the symmetries discussed in this paper can be understood as the Hamiltonian symmetries, which ensures their all-order validity and applicability to varying density matter.Show more - Symmetry in Neutrino Oscillation in Matter: New Picture and the νSM-Non-Unitarity InterplayMinakata, Hisakazu (MDPI, 2022-12-06)
Show more We update and summarize the present status of our understanding of the reparametrization symmetry with an i↔j state exchange in neutrino oscillation in matter. We introduce a systematic method called “Symmetry Finder” (SF) to uncover such symmetries, demonstrate its efficient hunting capability, and examine their characteristic features. Apparently they have a local nature: the 1–2 and 1–3 state exchange symmetries exist at around the solar and atmospheric resonances, respectively, with the level-crossing states exchanged. However, this view is not supported, to date, in the globally valid Denton et al. (DMP) perturbation theory, which possesses the 1–2, but not the 1–3, exchange symmetry. This is probably due to our lack of understanding, and we find a clue for a larger symmetry structure than we know of. In the latter part of this article, we introduce non-unitarity, or unitarity violation (UV), into the νSM neutrino paradigm, a low-energy description of beyond νSM new physics at a high (or low) scale. Based on the analyses of UV extended versions of the atmospheric resonance and the DMP perturbation theories, we argue that the reparametrization symmetry has a diagnostic capability for the theory with the νSM and UV sectors. Speculation is given on the topological nature of the identity, which determines the transformation property of the UV α parameters.Show more - Toward diagnosing neutrino non-unitarity through CP phase correlationsMinakata, Hisakazu (Oxford University Press, 2022-06-14)
Show more We discuss correlations between the neutrino-mass-embedded Standard Model CP phase d and the phases that originate from new physics which cause neutrino-sector unitarity violation (UV) at low energies. This study aims to provide one of the building blocks for machinery to diagnose non-unitarity, our ultimate goal. We extend the perturbation theory of neutrino oscillation in matter proposed by Denton et al. (DMP) to include the UV effect expressed by the alpha parametrization. By analyzing the DMP-UV perturbation theory to first order, we are able to draw a complete picture of the delta-UV phase correlations in the whole kinematical region covered by terrestrial neutrino experiments. Two regions exist with characteristically different patterns of the correlations: (i) the chiral-type [e(-i delta)alpha(mu e), e(-i delta)alpha(tau e), alpha(tau mu)] (Particle Data Group convention) correlation in the entire high-energy region vertical bar rho E vertical bar greater than or similar to 6 (g/cm(3)) GeV, and (ii) (blobs of the a parameters)-e(+/- i delta) correlation anywhere else. Some relevant aspects for the measurement of the UV parameters, such as the necessity of determining all the alpha(beta gamma) elements at once, are also pointed out.Show more