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Unraveling the Mystery of the Birth of the Universe with Neutrons
—Understanding Enhancement Mechanism of Symmetry Violation in Nuclei using Polarized Epithermal Neutrons with high intensity—

It has been suggested theoretically that extremely large enhancement of symmetry violation of particles and antiparticles in the neutron absorption reaction by nuclei. However, the detailed mechanism has not yet been completely elucidated.

In order to investigate this mechanism, it is necessary to study neutron absorption reaction using a spin-correlated (polarized) high-energy neutron (epithermal neutron) beam with high intensity.

Therefore, we irradiated nuclei with a polarized epithermal-neutron beam by installing a polarization device on a neutron beamline at J-PARC to study the neutron absorption reaction. As a result, we discovered, for the first time in the world, that emitted gamma rays have angular dependence depending on neutron spin direction in polarized-neutron absorption reaction by nuclei.

This result is an important information to reveal the enhancement mechanism of the symmetry violation in the nuclei, and theoretical study is undergoing. This enhancement mechanism is applicable to search for unknown physics, which can be related to the mystery of the birth of the universe, and an experiment to search for unknown physics using neutron and nuclei is planning. Additionally, the polarization technique of epithermal neutrons will be wildly used in various fields such as condensed matter physics and engineering.

Neutron polarization device installed on upstream of gamma-ray detectors (3He spin filter)

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