Speaker
Description
The hadronic weak interaction provides unique probe of the strong dynamics that confine quarks into nucleons in the low energy non-perturbative QCD regime. Precision measurements of parity violating observables in few body NN systems can provide important benchmarks for models that aim to describe this low-energy non-perturbative QCD regime, as well as effective models that seek to describe the NN weak interaction itself. Recent theoretical work [1,2] implies a large parity-odd neutron spin rotation (NSR) in $^{4}$He just outside the previous measurement of $d\phi/dz = [+2.1 \pm 8.3(stat.) \pm 2.9(sys.)] \times 10^{-7}$ rad/m [3]. Upgrades to the NSR apparatus enable an experimental sensitivity of less than $[\pm 1.0(stat.) \pm 1.0(sys.)] \times 10^{-7}$ rad/m [4] on the NG-C beamline at NIST. The status of the NSR apparatus as well as implications of the recent measurements of the weak pion exchange component of the NN weak interaction [5] and in the n-$^{3}$He system [6] will be discussed.
[1] S. Gardner, W. C. Haxton, and B. R. Holstein, Ann. Rev. Nucl. Part. Sci. ${\bf 67}$, 69 (2017).
[2] R. Lazauskas and Y.-H Song, Phys. Rev. C ${\bf 99}$, 054002 (2019).
[3] H. E. Swanson ${\it et \hspace{1mm} al.}$, Phys. Rev. C ${\bf 100}$, 015204 (2019).
[4] W. M. Snow ${\it et \hspace{1mm} al.}$, Rev. Sci. Inst. ${\bf 94}$, 055101, (2015).
[5] D. Blyth ${\it et \hspace{1mm} al.}$ (NPDGamma Collaboration), Phys. Rev. Lett. ${\bf 121}$, 242002 (2018).
[6] M. T. Gericke ${\it et \hspace{1mm} al.}$ (n$^3$He Collaboration), Phys. Rev. Lett. ${\bf 125}$, 131803 (2020).
