Laboratory for Particle Properties (Phi-lab)
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Neutron Lifetime measurement

under constraction Neutron lifetime τ is one of the absolutely critical parameter Cabibbo-Kobayashi-Masukawa行列のユニタリティ検証や ビッグバン元素合成理論

Now, Neutron Lifetime had been measured by two different method. But there is a considerable gap in these two observation results.

Then, we measure Neutron Lifrtime day-to-day by Electron Counting method that differs from these two methods, aiming to the accuracy 0.1% observation.
Electron Counting method is that we measure the neutron flux by
\begin{align} \rm {}^{3}He(n,p){}^{3}H \end{align} reaction and count the number of β decay by the β decay electrons.
We can evaluate Netron Lifetime by the function. \begin{align} \rm \tau_{n}=\frac{1}{\rho\sigma_{0}\it{v}_{0}}\left(\frac{S_{He}/\epsilon_{He}}{S_{\beta}/\epsilon{\beta}}\right) \end{align}

But we know that the current appratus cannot perform the accuracy 0.1% measurement, so we plan to increase the incident beam intensity to improve the statistical acuracy.