experimentally the study if p-p scattering is capable of much higher accuracy than n-p scattering, why?
There are two reasons for that 1. It is almost impossible to control neutron beam, as neutrons are neutral. It's also hard to get beam with energy you want, because you can not accelerate them. Thus, there is much less possibilities to control the experiment and so we have less accuracy. 2. As neutrons are neutral they are much harder to detect. They interact with matter much less then protons. So neutron detectors have less accuracy.