1. The problem statement, all variables and given/known data In a pp differential cross section, we have the differential cross section dσ/dΩ = 0.111 b/steradian at a lab energy of 4.3 MeV and a lab scattering angle of 30°. What is the s wave phase shift δ? 2. Relevant equations dσ/dΩ = sin2δ / k2  k = (2mE)(1/2) / h  3. The attempt at a solution Am I using the correct equations? Also, I haven't been given any value for m. Should I just use a proton's mass? I am basically using eqn 1 to get the phase shift. Also, I realized that I didn't use the scattering angle of 30° at all..