Evidence for three nucleon force effects in $p-d$ elastic scattering

A new measurement of the $p-d$ differential cross section at $E_p=1\mathrm{}\hspace{0.5em}\mathrm{MeV}$ has been performed. These new data and older data sets at energies below the deuteron breakup are compared to calculations using the two-nucleon Argonne $v_{18}$ and the three-nucleon Urbana IX potentials. A quantitative estimate of the capability of these interactions to describe the data is given in terms of a ${\chi }^2$ analysis. The ${\chi }^2$ per datum drastically improves when the three-nucleon interaction is included in the Hamiltonian.