Heavy neutrino mixing in the T2HK, the T2HKK and an extension of the T2HK with a detector at Oki Islands

We study the discovery potential for the mixing of heavy isospin-singlet neutrinos in extensions of the Tokai-to-Kamioka (T2K) experiment: The Tokai-to-Hyper-Kamiokande (T2HK), the Tokai-to-Hyper-Kamiokande-to-Korea (T2HKK), and a plan of adding a new detector at Oki Islands to the T2HK. We parametrize the mixing of heavy neutrinos in terms of a non-unitary mixing matrix acting on active flavors. It is shown that in the T2HK and T2HKK, the sensitivity to heavy neutrino mixing deteriorates for some values of $CP$-violating phases in the standard and the non-unitary mixing matrices, but the deterioration is drastically mitigated if a detector at Oki Islands is added to the T2HK. We also consider the feasibility of measuring the mass hierarchy and the standard $CP$-violating phase $\delta_{CP}$ in the presence of heavy neutrino mixing, by fitting experimental data with the standard oscillation parameters only, i.e., under the assumption of unitary mixing. It is revealed that such measurement can be performed to some accuracy in the T2HKK and the extension of the T2HK with a detector at Oki Islands, owing to the fact that data with largely varying $L/E$ are collected in these experiments, while it cannot be in the T2HK.Comment: 41 pages, 16 figures. Version accepted for publication in EPJ

Radion stabilization in the presence of Wilson line phase

We study the stabilization of an extra-dimensional radius in the presence of a Wilson line phase of an extra $U(1)$ gauge symmetry on a five-dimensional space-time, using the effective potential relating both the radion and the Wilson line phase at the one-loop level. We find that the radion can be stabilized by the introduction of a small number of fermions.Comment: 12 pages, 5 figures, Comments added. References added. Typo correcte

High-energy properties of the graviton scattering in quadratic gravity

We obtain the matter-graviton scattering amplitude in the gravitational theory of quadratic curvature, which has $R_{\mu\nu}^2$ term in the action. Unitarity bound is not satisfied because of the existence of negative norm states, while an analog of unitarity bound for $S$-matrix unitarity holds due to the cancelation among the positive norm states and negative norm ones in the unitarity summation in the optical theorem. The violation of unitarity bound is a counter example of Llewellyn Smith's conjecture on the relation between tree-level unitarity and renormalizability. We have recently proposed a new conjecture that an analog of the unitarity bound for $S$-matrix unitarity gives the equivalent conditions to those for renormalizability. We show that the gravitational theory of quadratic curvature is a nontrivial example consistent with our conjecture.Comment: 61pages, 3 figure

Gravity Loop Corrections to the Standard Model Higgs in Einstein Gravity

We study one-loop quantum gravity corrections to the standard model Higgs potential $V(\phi) \grave{\rm a}$ la Coleman-Weinberg and examine the stability question of $V(\phi)$ in the energy region of Planck mass scale, $\mu\simeq M_{\rm Pl}$ $(M_{\rm Pl}=1.22\times10^{19}{\rm GeV})$. We calculate the gravity one-loop corrections to $V(\phi)$ in Einstein gravity by using the momentum cut-off $\Lambda$. We have found that even small gravity corrections compete with the standard model term of $V(\phi)$ and affect the stability argument of the latter part alone. This is because the latter part is nearly zero in the energy region of $M_{\rm Pl}$

RETRATO SIN IDENTIFICAR [Material gráfico]

Copia digital. Madrid : Ministerio de Educación, Cultura y Deporte. Subdirección General de Coordinación Bibliotecaria, 201