Quasivacuum solar neutrino oscillations

TL;DR

This paper investigates solar neutrino oscillations in a quasi-vacuum regime, emphasizing matter effects and providing numerical corrections for accurate modeling across different oscillation regimes.

Contribution

It introduces a detailed analysis of matter effects in quasi-vacuum neutrino oscillations and offers practical prescriptions for incorporating these corrections in data analysis.

Findings

Matter effects are significant in the quasi-vacuum regime.

Exponential approximation overestimates matter effects compared to true density profiles.

Corrections improve the accuracy of solar neutrino oscillation models.

Abstract

We discuss in detail solar neutrino oscillations with \delta m^2/E in the range [10^-10,10^-7] eV^2/MeV. In this range, which interpolates smoothly between the so-called ``just-so'' and ``Mikheyev-Smirnov-Wolfenstein'' oscillation regimes, neutrino flavor transitions are increasingly affected by matter effects as \delta m^2/E increases. As a consequence, the usual vacuum approximation has to be improved through the matter-induced corrections, leading to a ``quasi-vacuum'' oscillation regime. We perform accurate numerical calculations of such corrections, using both the true solar density profile and its exponential approximation. Matter effects are shown to be somewhat overestimated in the latter case. We also discuss the role of Earth crossing and of energy smearing. Prescriptions are given to implement the leading corrections in the quasi-vacuum oscillation range. Finally, the results are applied to a global analysis of solar nu data in a three-flavor framework.