The discovery of neutrino oscillations has opened a new chapter in particle physics. The observation of this phenomenon implies that neutrinos have non-zero masses, a property not accounted for in the Standard Model. The mechanism most widely-used to model neutrino oscillations uses a mixing matrix formalism, similar to the one in the quark sector. The probability of neutrino flavor oscillations depends on the size of the elements of this matrix, as well as the difference between the neutrino mass states. By measuring neutrinos from both natural and artificial sources, experiments over the past two decades have been able to measure the parameters describing neutrino oscillations with varying degrees of precision. The least well known oscillation parameters which remain to be probed are most accessible by using well understood and controlled neutrino beams from accelerators. Experiments which use this technique are sensitive, in particular, to the neutrino mass ordering and the complex CP-violating phase, dCP. The latter, in particular, determines whether CP symmetry is violated in the lepton sector, while the former will shed light on the neutrino mass ordering problem. The same experiments which tackle these challenges are well equipped to search for physics beyond the mixing matrix formalism.
Current long-baseline neutrino oscillation experiments (T2K and NOvA) measure oscillation parameters by comparing the evolution of the flavor composition in a pure (anti-)neutrino beam. The oscillation probability evolves as a function of neutrino energy. However, the neutrino energy spectrum measured in these experiments is also determined by the neutrino flux, detector efficiency effects, and the cross-section of neutrino interactions with the target nuclei. The latter introduce sources of systematic uncertainty, whose mis-modelling can severely bias neutrino oscillation parameter measurements. Of the three, the physics of neutrino interactions with matter represents the dominant source of systematic uncertainty.
This seminar will illustrate the mechanisms through which neutrino-nucleus interactions affect neutrino oscillation measurements in current and future long-baseline experiments. Next-generation experiments, such as DUNE and Hyper-Kamiokande, are being developed with extremely ambitious precision physics goals. If kept at current levels, neutrino-nucleus interaction systematic uncertainties will quickly become the limiting factor to their physics programs. This talk will present an overview of experimental and theoretical programs aimed at mitigating these uncertainties as neutrino physics enters the precision measurement era.
Oscar Blanch, Andreu Font Ribera, Lluisa-Maria Mir, Rafel Escribano