https://doi.org/10.1051/epjconf/201921903003
New project for precise neutron lifetime measurement at J-PARC
1 Department of Physics, Graduate School of Science, The University of Tokyo, Japan
2 Department of Physics, Graduate School of Science, Nagoya University, Japan
3 KEK, High Energy Accelerator Research Organization, Japan
4 Institute for Chemical Research, Kyoto University, Japan
5 Kobayashi-Maskawa Institute for the Origin of Particles and the Universe (KMI), Nagoya University, Japan
6 Department of Physics, Graduate School of Science, Kyoto University, Japan
7 Department of Physics, Graduate School of Science, Kyushu University, Japan
8 Istituto Nazionale di Fisica Nucleare (INFN-Genova), Japan
9 Research Center for Advanced Particle Physics (RCAPP), Kyushu University, Japan
10 J-PARC Center, Japan Atomic Energy Agency, Japan
11 Institute of Applied Physics, University of Tsukuba, Japan
12 Research Center for Nuclear Physics (RCNP), Osaka University, Japan
13 Department of Basic Science, Graduate School of Arts and Sciences, The University of Tokyo, Japan
14 International Center for the Elementary Particle Physics (ICEPP), The University of Tokyo, Japan
a e-mail: nagakura@icepp.s.u-tokyo.ac.jp
Published online: 12 December 2019
The decay lifetime of free neutrons (∼880 s) is an important parameter of the weak interaction and for Big Bang Nucleosynthesis. However, results of measurements currently show discrepancies depending on the method used. As most experiments nowadays employ ultra cold neutrons, we have developed a new cold-beam experiment which we perform at the Japan Proton Accelerator Research Complex. As a special feature, a polarized neutron beam is bunched by a spin flip chopper. A time projection chamber operated with He and CO2 gas, including a well-controlled amount of 3He, is used for detection of the beta-decays and simultaneous determination of the beam intensity. Using the data between 2014 and 2016, we evaluated our first, preliminary result of the neutron lifetime as 896 ± 10(stat.) −10+14(sys.) s. We plan several upgrades to achieve our precision goal of 1 s.
© The Authors, published by EDP Sciences, 2019
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