Issues in mass hierarchy discrimination via reactor neutrino oscillations

Title: Issues in mass hierarchy discrimination via reactor neutrino oscillations

Presenter:  Eligio Lisi (INFN Bari)

Abstract: We revisit some issues related to the precision calculation and the statistical analysis of reactor neutrino spectra, in the context of medium baseline experiments aiming at discriminating the neutrino mass hierarchy.

Concerning precision calculations, we cast the oscillation probability in an analytical form which makes manifest hierarchy, damping and matter effects; we also include recoil effects through analytic modifications of the energy resolution function. 

Concerning the statistical analysis, we introduce a parameter alpha which interpolates smoothly between normal hierarchy (alpha=+1) and inverted hierarchy (alpha=-1), thus covering undesirable but possible outcomes of "undecidable" hierarchy (alpha ~ 0). We apply these ingredients to the analysis of a prospective JUNO-like experiment, including geoneutrino and far-reactor contributions.

We show the accuracy reachable on the electron-neutrino oscillation parameters, and discuss the sensitivity to the hierarchy, which is estimated around the ~2sigma level (in terms of the distance from true hierarchy to undecidable hierarchy).

Finally, we discuss the subtle and challenging systematics related to the energy scale nonlinearity, and their interplay with spectral shape uncertainties. Based on the paper arXiv:1309.1638 by F. Capozzi, E.

Lisi and A. Marrone.

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