Speaker
Description
We recently performed measurements of the neutron incoherent scattering lengths for $^{129}$Xe and $^{131}$Xe. As a part of those measurements the $\Delta b_i$ of $^3$He was also measured for a short time, only 6 hours, as a calibration. The results of this measurement indicate a very precise value could be obtained for a typical length experiment on NSE. Theories which take the data from measurements in three-body nuclear systems and predict what should be seen in a 4-body system like $^4$He or n-$^3$He, which is an essential step needed to check the internal consistency of the three-body force extraction from systems with only three bodies, do not quite agree with the data by amounts too large to be explained only by 4-body forces. Furthermore, in the specific case of the n-$^3$He system, the two best measurements of the n-$^3$He incoherent scattering length differ by 3$\sigma$. During the course of our test measurement we found several important experimental and theoretical factors relevant to a measurement with precision beyond the error of the current measurements. We estimate that we could obtain a 1% measurement for $b_i$ of $^3$He in one week.
