Modern Physics Letters A

T2K is the first of a new generation of long baseline neutrino oscillation experiments that will measure neutrino oscillations parameters. The experiment uses the J-PARC accelerator complex on the east cost of Japan to sent a neutrino beam to the Kamioka mine, located 295 km to the west. It consists of a dedicated beam-line, a near detector complex to characterize the beam and the well-known Super-Kamiokande detector to measure the oscillation signal. This paper describes the experimental setup, the results of the first measurement campaign as well as giving an outlook on the future potential of the experiment.

In this paper we investigate a tachyon field model in cosmology, provided its interaction with the quintessence or phantom fields. The model takes into account this interaction beyond the usual approach, in which the interaction is phenomenologically described by the energy flow between the matter components. In our model, the interaction of tachyon field with a canonical scalar field is taken into account through the interaction potential in the total Lagrangian of the system, like in the case of two or more canonical scalar fields. We obtain the different types of exact solution for the model by employing the so-called "first order formalism" procedures.

Unlike all the previous studies on proton decay which worked only in the Minimal Supersymmetric Standard Model, we study the effects of the dimension-5 operators in the Supersymmetric Unification Models with left–right symmetry at low energy. The full chargino sector is used for the analysis. Dressing of the RRRR operators by the SU(2)_R wino makes important or even dominant contributions to the proton decay modes into charged leptons.

We make an explicit calculation of Casimir effect through an alternative approach of field quantization for a spherical shell in which only the radial part of fluctuation has been taken into account. In this method, negative norm states have been utilized to obtain a natural renormalized theory with the condition that they cannot be affected by the physical boundary conditions. It is shown that by using this method, the exact result is obtained without any appearance of infinity.

We consider the regularization of a gauge quantum field theory following a modification of the Pochinski proof based on the introduction of a cutoff function. We work with a Poincaré invariant deformation of the ordinary pointwise product of fields introduced by Ardalan, Arfaei, Ghasemkhani and Sadooghi, and show that it yields, through a limiting procedure of the cutoff functions, to a regularized theory, preserving all symmetries at every stage. The new gauge symmetry yields a new Hopf algebra with deformed costructures, which is inequivalent to the standard one.

We study a simple higher-dimensional toy model of electroweak symmetry breaking, in particular a pure gauge 5D theory on flat background with one extra finite space dimension. The principle of least action and the requirement of gauge independence of scattering amplitudes are used to determine the possible choices of boundary conditions. We demonstrate that for any of these choices the scattering amplitudes of vector bosons do not exhibit power-like growth in the high energy limit. Our analysis is an extension and generalization of the results obtained previously by other authors.