Abstract
We investigate the effect induced by the variation of the density profile of the Earth's interior in a long baseline neutrino oscillation experiment. In the first instance, we point out two facts; The most essential part of the matter profile is the first Fourier mode of the matter profile function. The Earth models based on the study of the seismology include large uncertainty for the first Fourier mode. Next, we show that there is a strong correlation between the average density value and the first Fourier coefficient in the analyses on the oscillation probability. This means that the matter profile effect induces extra uncertainty for average matter parameter. Taking into account this extra uncertainty, we make numerical calculations for the sensitivity to CP violation search. The results show that the CP sensitivity is impaired in large U_<e3> region.
