Testing the three massive neutrino paradigm: Constraints on Neutrino Properties and Interactions from Recent Experimental Data

Abstract

Neutrino physics offers unique insights into phenomena beyond the Standard Model (BSM). This thesis presents phenomenological investigations organized around three pillars: consolidation of the three-flavor oscillation paradigm, exploration of new physics viability, and precise determination of solar neutrino fluxes. The theoretical framework introduces massive neutrinos, leptonic mixing, and flavor transitions, followed by experimental results emphasizing Borexino and NOvA data analyses. The first pillar establishes the three-flavor framework through global analysis of solar, atmospheric, reactor, and accelerator data, providing updated determinations of mixing angles ($θ_{12}$, $θ_{13}$, $θ_{23}$) and mass-squared differences ($Δm^2_{21}$, $Δm^2_{31}$), while quantifying ambiguities in mass ordering and $θ_{23}$ octant. The second pillar investigates Non-Standard Interactions (NSI) with electrons and quarks, combining Borexino data with COHERENT's CE$ν$NS measurements to establish bounds on propagation and detection couplings, excluding viable NSI parameter regions including potential LMA-D solutions. The third pillar advances solar neutrino physics through precision flux determinations, integrating pp-chain and CNO-cycle measurements. Results show preference for high-metallicity Standard Solar Models and incompatibility between $3+1$ mixing parameters favored by Gallium experiments and solar observations. This synthesis guides future experiments toward resolving mass ordering, CP violation, and dark sector interactions.

Figures (58)

• Figure 1: Convention for the numbering of mass eigenstates and possible orderings (NO in left, IO in right). The colours indicate the amount of mixing between mass and flavour eigenstates as obtained from the global analysis of neutrino oscillation experiments as we will describe and quantify in Chapters \ref{['chap:exp']} and \ref{['cap:nufit']}
• Figure 2: Neutrino fluxes predicted by the SSMBahcall:2004pz as a function of the neutrino energy. Figure extracted from Concha2.
• Figure 3: Left: our choice of the energy resolution function, based on the relation between $\sigma_h$ and $\bar{N}_h$ inferred from the upper panel of Fig. 22 of Ref.Borexino:2017rsf. Right: our reconstruction of solar spectra after the optimization of the energy scale function.
• Figure 4: Spectrum for the best-fit normalizations of the different components obtained from our fit to the (upper panel) Borexino Phase II data for TFC-subtracted (left) and TFC-tagged events and (lower panel) Borexino Phase III data for TFC-subtracted (left) and TFC-tagged events.
• Figure 5: Dependence of our $\Delta\chi^2$ for the fit to the Borexino phase-II spectra on the normalization of the solar fluxes and the dominant backgrounds (normalized to the corresponding best fit normalizations of the fit of the Borexino collaboration in Ref.Borexino:2017rsf). For comparison we show as light blue curves the corresponding results of the determination of solar fluxes in Ref.Borexino:2017rsf) (see text for details).