First indication of terrestrial matter effects on solar neutrino oscillation

Prospects for the Detection of the Diffuse Supernova Neutrino Background with the Experiments SK-Gd and JUNO

The advent of gadolinium-loaded Super-Kamiokande (SK-Gd) and of the soon-to-start JUNO liquid scintillator detector marks a substantial improvement in global sensitivity for the Diffuse Supernova Neutrino Background (DSNB). The present article reviews the detector properties most relevant for the DSNB searches in both experiments and estimates the expected signal and background levels. Based on these inputs, we evaluate the sensitivity of both experiments individually and combined. Using a simplified statistical approach, we find that both SK-Gd and JUNO have the potential to reach >3σ evidence of the DSNB signal within 10 years of measurement. Combination of their results is likely to enable a 5σ discovery of the DSNB signal within the next decade.

New Opportunities at the Next-Generation Neutrino Experiments (Part 1: BSM Neutrino Physics and Dark Matter

With the advent of a new generation of neutrino experiments which leverage high-intensity neutrino beams for precision neutrino oscillation parameter and for CP violation phase measurements, it is timely to explore physics topics beyond the standard neutrino-related physics. Given that beyond the standard model (BSM) physics phenomena have been mostly sought at high-energy regimes, such as the LHC at CERN, the exploration of BSM physics in neutrino experiments will enable complementary measurements at the energy regimes that balance that of the LHC. This is in concert with new ideas for high-intensity beams for fixed target and beam-dump experiments world-wide. The combination of the high intensity beam facilities and large mass detectors with highly precise track and energy measurements, excellent timing resolution, and low energy thresholds will help make BSM physics reachable even in low energy regimes in accelerator-based experiments and searches for BSM phenomena from cosmogenic origin. Therefore, it is conceivable that BSM topics could be the dominant physics topics in the foreseeable future. In this spirit, this paper provides a review of the current theory landscape theory in neutrino experiments in two selected areas of the BSM topics - dark matter and neutrino related BSM - and summarizes the current results from existing neutrino experiments for benchmark. This paper then provides a review of upcoming neutrino experiments and their capabilities to set the foundation for potential reach in BSM physics in the two themes. One of the most important outcomes of this paper is to ensure theoretical and simulation tools exist to perform studies of these new areas of physics from the first day of the experiments, such as DUNE and Hyper-K. Tasks to accomplish this goal, and the time line for them to be completed and tested to become reliable tools in a timely fashion are also discussed.

The Sun, neutrinos and Super-Kamiokande

In the standard model of elementary particle physics neutrinos are massless, and therefore the actuality of finite neutrino mass indicates a theory beyond the standard model. The Sun produces abundant neutrinos due to nuclear fusion reactions. A pioneering experiment in the early '70s detected neutrinos from the Sun, but found that the observed flux was smaller than expected, which was then called the missing solar neutrino problem. Tremendous efforts were made both experimentally and theoretically to solve this problem. In 2001, almost 30 years after the first indication, data from Super-Kamiokande in Japan and SNO in Canada together provided evidence that neutrino oscillation effectively converts the solar (electron) neutrinos to non-electron type neutrinos. Neutrino oscillation can occur only for those neutrinos with finite neutrino mass.

Reception of Modulated Neutrino Day-Night Effect Signal by Neutrino Detectors

The regeneration effect of solar neutrinos in the Earth leading to the so-called day-night effect strongly depends on the neutrino energy, the time of day, and the season. Classical neutrino experiments, such as Super-Kamiokande, typically observe this effect cumulatively, i.e., virtually integrate it over the year. We discuss various day-night effects that could become potentially observable if time-weighted data processing is applied to neutrino events. The procedure is similar to reception of radio-frequency modulated signals and ‘demodulation’ of the neutrino signal, for example, is able to reveal interesting signatures in the high-energy tail of the electron recoil energy spectrum

Projections for Measuring the Size of the Solar Core with Neutrino-Electron Scattering

We quantify the amount of data needed in order to measure the size and position of the ^{8}B neutrino production region within the solar core, for experiments looking at elastic scattering between electrons and solar neutrinos. The directions of the electrons immediately after scattering are strongly correlated with the incident directions of the neutrinos; however, this is degraded significantly by the subsequent scattering of these electrons in the detector medium. We generate distributions of such electrons for different neutrino production profiles, and use a maximum likelihood analysis to make projections for future experimental sensitivity. We find that with approximately 20 years worth of data the Super Kamiokande experiment could constrain the central radius of the shell in which ^{8}B neutrinos are produced to be less than 0.22 of the total solar radius at 95% confidence.