No Arabic abstract
As a result of a non-trivial mixing matrix, neutrinos cannot be simultaneously in a flavor and mass eigenstate. We formulate and discuss information entropic relations that quantify the associated quantum uncertainty. We also formulate a protocol to determine the Pontecorvo-Maki-Nakagawa-Sakata (PMNS) matrix from quantum manipulations and measurements on an entangled lepton-neutrino pair. The entangled state features neutrino oscillations in a conditional probability involving measurements on the lepton and the neutrino. They can be switched off by choosing a specific observable on the lepton side which is determined by the PMNS matrix. The parameters of the latter, including the CP-violating phase $delta$, can be obtained by guessing them and improving the guess by minimizing the remaining oscillations.
We analyze the different parametrizations of a general four-zero texture mass matrices for quarks and leptons, that are able to reproduce the CKM and PMNS mixing matrices. This study is done through a Chi-Square analysis. In quark sector, only four solutions are found to be compatible with CKM mixing matrix. In leptonic sector, using the last experimental results about the mixing angles in the neutrino sector, our Chi-Square analysis shows a preferred value for m_nu_3 to be around 0.05 eV independently of the parametrization of the four-zero texture mass matrices chosen for the charged leptons and neutrinos.
The residual symmetry approach, along with a complex extension for some flavor invariance, is a powerful tool to uncover the flavor structure of the $3times3$ neutrino Majorana mass matrix $M_ u$ towards gaining insights into neutrino mixing. We utilize this to propose a complex extension of the real scaling ansatz for $M_ u$ which was introduced some years ago. Unlike the latter, our proposal allows a nonzero mass for each of the three light neutrinos as well as a nonvanishing $theta_{13}$. A major result of this scheme is that leptonic Dirac CP-violation must be maximal while atmospheric neutrino mixing need not be exactly maximal. Moreover, each of the two allowed Majorana phases, to be probed by the search for nuclear $0 u betabeta$ decay, has to be at one of its two CP-conserving values. There are other interesting consequences such as the allowed occurrence of a normal mass ordering which is not favored by the real scaling ansatz. Our predictions will be tested in ongoing and future neutrino oscillation experiments at T2K, NO$ u$A and DUNE.
We discuss what kinds of combinations of Yukawa interactions can generate the Majorana neutrino mass matrix. We concentrate on the flavor structure of the neutrino mass matrix because it does not depend on details of the models except for Yukawa interactions while determination of the overall scale of the mass matrix requires to specify also the scalar potential and masses of new particles. Thus, models to generate Majorana neutrino mass matrix can be efficiently classified according to the combination of Yukawa interactions. We first investigate the case where Yukawa interactions with only leptons are utilized. Next, we consider the case with Yukawa interactions between leptons and gauge singlet fermions, which have the odd parity under the unbroken Z_2 symmetry. We show that combinations of Yukawa interactions for these cases can be classified into only three groups. Our classification would be useful for the efficient discrimination of models via experimental tests for not each model but just three groups of models.
We classify models of the Dirac neutrino mass by concentrating on flavor structures of the mass matrix. The advantage of our classification is that we do not need to specify detail of models except for Yukawa interactions because flavor structures can be given only by products of Yukawa matrices. All possible Yukawa interactions between leptons (including the right-handed neutrino) are taken into account by introducing appropriate scalar fields. We also take into account the case with Yukawa interactions of leptons with the dark matter candidate. Then, we see that flavor structures can be classified into seven groups. The result is useful for the efficient test of models of the neutrino mass. One of seven groups can be tested by measuring the absolute neutrino mass. Other two can be tested by probing the violation of the lepton universality in $ell to ell^prime u overline{ u}$. In order to test the other four groups, we can rely on searches for new scalar particles at collider experiments.
Using the Mandelstam-Tamm method we derive time-energy uncertainty relations for neutrino oscillations. We demonstrate that the small energy uncertainty of antineutrinos in a recently considered experiment with recoilless resonant (Mossbauer) production and absorption of tritium antineutrinos is in conflict with the energy uncertainty which, according to the time-energy uncertainty relation, is necessary for neutrino oscillations to happen. A Mossbauer neutrino experiment could provide a unique possibility to test the applicability of the time-energy uncertainty relation to neutrino oscillations and to reveal the true nature of neutrino oscillations.