Neutrino-Resonant Oscillations in the Earth, and the ν _e /ν _μ Ratio in Upward-Going Atmospheric Neutrino Fluxes

Abstract

We evaluate the conversion probability for neutrinos by solving the evolution equations with a numerical method, taking into account a density distribution of the Earth, and calculate an upward-going neutrino flux ratio (νe +ν̄e)/(νμ +ν̄μ) by using the recent values of atmospheric neutrino fluxes, where the updated ratios νμ/ν̄μ and νe/ν̄e have been taken into account. It is found that the ratio, including the effect of neutrino-resonant oscillations, can well explain the Kamiokande data for ϕ = 0° and 30°, and the NUSEX and the Fréjus data (averaged over ϕ) at energies around 1 GeV, whilst the ratio with no neutrino oscillations or with the muon polarization cannot explain the measured data.

Three-flavor atmospheric neutrino anomaly

“…However, the vacuum approximation is not adequate for neutrinos which travel in the earth matter for a large fraction of their path length. For these neutrinos one expects substantial deviations from the vacuum oscillation probability [42][43][44][45][46]23] when…”

Reconstruction of the Earth's matter density profile using a single neutrino baseline

“…Neutrino oscillations in the Earth have been extensively studied in general and it has been suggested that neutrino oscillations in matter can severely alter the energy spectrum of a neutrino beam through the Earth for long baselines [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. For quite realistic calculations of the transition probabilities the Preliminary Reference Earth Model (PREM) or similar matter density profiles have been used [31,32].…”