Toward to the neutron lifetime puzzle, the 3rd method was launched



High Energy Accelerator Research Organization (KEK)

Japan Proton Accelerator Research Complex (J-PARC)

Nagoya University

The University of Tokyo

Kyoto University

Kyushu University

University of Tsukuba

Osaka University



Key points of this research results

-We have developed an apparatus for the neutron lifetime measurement with a new method and obtained the first experimental results.

-The neutron lifetime puzzle will be solved by improving the accuracy in future.



A research group led by Kenji Mishima, Takashi Ino, and Go Ichikawa at the Institute for Materials Structure Science of the High Energy Accelerator Research Organization (KEK), in collaboration with Nagoya University, the University of Tokyo, Kyoto University, Kyushu University, Osaka Electro-Communication University, University of Tsukuba, and Osaka University, has developed an apparatus to measure the neutron lifetime using a new method different from existing ones, and obtained the first experimental results.

The decay of neutrons, one of the particles that form the nucleus, is deeply related to the mechanism of the synthesis of elements in the universe and to particle physics. By improving the measurement accuracy of neutron decay lifetimes based on the results of this research, it is hoped that the mysteries of the evolution of the universe will be further explored.

The research results are scheduled to be published in the journal “Progress of Theoretical and Experimental Physics” on January 8th, 2021.



Fig.3: The results of the neutron lifetime obtained previous experiments by the beam (green), bottle (blue) methods, and by the present experiment.




Please refer to the  press release for details.