The Prediction of the Atmospheric Neutrino Fluxes

Abstract

A consensus has emerged that the existing data on atmospheric neutrinos shows convincing evidence for the “disappearance” of v ^μ and $\bar v_\mu$ that requires the existence of some form of “new physics” beyond the standard model. The evidence for the existence of new physics is based on the observation of three effects: (i) a measured μ/e ratio smaller that the expectation, (ii) the detection of a strong up/down asymmetry for μ-like events, and (iii) the distotion of the zenith angle distribution of μ-induced up-going muons. The atmospheric v fluxes have two properties that can be predicted in a model independent way: (1) the fluxes are up-down symmetric, that is $\varphi _{v_\alpha } (E_v ,\theta ) \simeq \varphi _{v_\alpha } (E_v ,\pi - \theta )$, (2) the fluxes of v _e and V _μ are strictly related. Therefore the qualitative results of SK[1] that show a suppression of μ-like relative to e-like events, and of up-going (long L) relative to down-going (short L) events can indeed be considered as a “smoking gun”, a model independent result that demands the existence of new physics. These results confirm the source of the “atmospheric neutrino anomaly” found by the first generation of water Cherenkov detectors 1MB and Kamioka. The SK claims are confirmed by the results of Soudan[2] and MACRO [3].