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Nao-aki Yamashita

Publications and source records attributed to Nao-aki Yamashita.

4 recordsLinked to original sources
arXiv2005

Effective Theory Approach to the Skyrme model and Application to Pentaquarks

The Skyrme model is reconsidered from an effective theory point of view. From the most general chiral Lagrangian up to including terms of order $p^4$, $N_c$ and $δm^2$ ($δm\equiv m_s-m$), new interactions, which have never been considered before, appear upon collective coordinate quantization. We obtain the parameter set best fitted to the observed low-lying baryon masses, by performing the second order perturbative calculations with respect to $δm$. We calculate the masses and the decay widths of the other members of (mainly) anti-decuplet pentaquark states. The formula for the decay widths is reconsidered and its baryon mass dependence is clarified.

hep-ph↗
arXiv2001

Oscillation enhanced search for new interaction with neutrinos

We discuss the measurement of new physics in long baseline neutrino oscillation experiments. Through the neutrino oscillation, the probability to detect the new physics effects such as flavor violation is enhanced by the interference with the weak interaction. We carefully explain the situations that the interference can take place. Assuming a neutrino factory and an upgraded conventional beam, we estimate the feasibility to observe new physics numerically and point out that we can search new interactions using some channels, for example $ν_μ \to ν_μ$, in these experiments. We also discuss several models which induce the effective interactions interfering with the weak interaction, and show that some new physics effects are large enough to be observed in the oscillation enhanced way.

hep-ph↗
arXiv2000

Mass Hierarchy from SU(1,1) Horizontal Symmetry

The new mechanism for the generation of the chiral generations is proposed based on the SU(1,1) horizontal gauge symmetry. The appearance of the chiral generations is controlled by the coupling constant s of the model. This is crucial in the grand unification scheme. The resulting chiral generations naturally acquire the hierarchal Yukawa coupli ng matrices. Propriety of the model to the observed hierarchical structure is discussed nume rically under the minimal parameter set.

hep-ph↗