Efficient Neutrino Oscillation Parameter Inference with Gaussian Process

Many experiments have been set-up to measure the parameters governing the neutrino oscillation probabilities accurately, with implications for the fundamental structure of the universe. Very often, this involves inferences from tiny samples of data which have complicated dependencies on multiple oscillation parameters simultaneously. This is typically carried out using the unified approach of Feldman and Cousins which is very computationally expensive, on the order of tens of millions of CPU hours. In this work, we propose an iterative method using Gaussian Process to efficiently find a confidence contour for the oscillation parameters and show that it produces the same results at a fraction of the computation cost.

The status of the Double Chooz experiment

Double Chooz is a long baseline neutrino oscillation experiment at Chooz, France. The purpose of this experiment is to measure the non-zero neutrino oscillation parameter θ13, a parameter for changing electron neutrinos into other neutrinos. This experiment uses reactors of the Chooz Nuclear Power Plant as a neutrino source. Double Chooz has published two papers with results showing the measurement of the mixing angle, and 3rd publication is processing.

REACTOR NEUTRINO EXPERIMENTS

Previous searches for neutrino oscillations with reactor neutrinos have been done only with baselines less than 1 km. The observed neutrino flux was consistent with the expectation and only excluded regions were drawn on the neutrino-oscillation-parameter space. Thus, those experiments played important roles in understanding neutrinos from fission reactors. Based on the knowledge from those experiments, an experiment with about a 180 km baseline became possible. Results obtained from this baseline experiment showed evidence for reactor neutrino disappearance and finally provide a resolution for the long standing solar neutrino problem when combined with results from the solar neutrino experiments. Several possibilities to explore the last unmeasured mixing angle θ13 with reactor neutrinos have recently been proposed. They will provide complementary information to long baseline accelerator experiments when one tries to solve the degeneracy of oscillation parameters. Reactor neutrinos are also useful to study the neutrino magnetic moment and the most stringent limits from terrestrial experiments are obtained by measuring the elastic scattering cross section of reactor neutrinos.

CONSTRAINTS ON NEUTRINO OSCILLATION PARAMETERS FROM TIME/ENERGY DEPENDENCE OF SOLAR 8B NEUTRINO FLUX

A search for neutrino oscillation is presented using time variations and energy dependence of the observed reduction of the solar neutrino flux. No significant time variation or energy dependence has been found in 1117 days of solar neutrino data taken with the Super-Kamiokande experiment. This constrains the two-neutrino oscillation parameter space independently of the model dependence of the solar neutrino flux. The combination of Super-Kamiokande's data of the day-night variation, energy dependence and flux results in two allowed regions at 95% C.L.