Proton -- $^{3}$He Elastic Scattering at Low Energies*

We present new accurate measurements of the differential cross section $\sigma(\theta)$ and the proton analyzing power $A_{y}$ for proton--$^{3}\mathrm{He}$ elastic scattering at various energies. The $\sigma(\theta)$ distributions have been measured at $E_{\mathrm{p}}$ = 0.99, 1.59, 2.24, 3.11, and 4.02 MeV. Full angular distributions of $A_{y}(\theta)$ have been measured at $E_{\mathrm{p}}$ = 1.60, 2.25, 3.13, and 4.05 MeV. This set of high-precision data is compared to four-body variational calculations employing realistic nucleon-nucleon ($NN$) and three-nucleon ($3N$) interactions. For the unpolarized cross section the agreement between the theoretical calculation and experimental data is good when a realistic $3N$ potential is included. However, the comparison between the calculated and measured proton analyzing powers reveals discrepancies of approximately 50\% at the maximum of each distribution.