Title: Geoneutrino sources and fluxes: A systematic approach to their uncertainties and correlations

(E. Lisi, work in collaboration with G.L. Fogli, A. Palazzo, and A.M. Rotunno - Univ. of Bari and INFN, Bari).

Abstract: Models and observables related to geoneutrinos involve, in general, highly (anti)correlated quantities. Examples of covariant quantities include the U, Th, and K abundances in any Earth reservoir, the radiogenic heat versus the neutrino luminosity, and the estimated geoneutrino fluxes in different detectors. Negative correlations arise instead among geoneutrino source abundances in complementary reservoirs (due to mass balance constraints in the Bulk Silicate Earth model) and between the U and Th event rates in a typical geoneutrino experiment (due to a prevailing sensitivity to the sum of U+Th events).

We propose a simple and systematic approach to the covariance matrices arising in the context of geoneutrino analyses, based on the fact that all the relevant observables and constraints can be expressed as linear functions of the U, Th and K abundances through relatively well-known coefficients. We construct first a "zeroth-order" GeoNeutrino Source Model (GNSM), embedding reasonable errors and correlations for the U, Th, and K abundances in relevant Earth reservoirs. The construction of such a GNSM, based on selected geophysical and geochemical data+models (when available), on plausible hypotheses (when possible) and, admittedly, on arbitrary assumptions (when unavoidable), shed light on some critical issues in the evaluation of geophysical and geochemical uncertainties and covariances.

We then show how the central values and the error matrix of such zeroth-order GNSM can be easily "updated" whenever new geoneutrino and geological data, as well as more refined mass-balance and heat-flow constraints, will become available in the future. Subsequent updates might either converge towards a more accurate "concordance GNRM," or diverge if some "tension" emerges among different inputs - possibly suggesting a GNSM revision. Alternative GNSMs (based, e.g., on "unorthodox" assumptions) could be similarly tested. In this context, our approach can provide a well-defined statistical framework for evaluating the global consistency of (future or prospective) geoneutrino data and models.