Nonlinear energy-loss straggling of protons and antiprotons in an electron gas

The electronic energy-loss straggling of protons and antiprotons moving at arbitrary nonrelativistic velocities in a homogeneous electron gas are evaluated within a quadratic response theory and the random-phase approximation. These results show that, at low and intermediate velocities, quadratic corrections significantly reduce the energy-loss straggling of antiprotons, these corrections being, at low velocities, more important than in the evaluation of the stopping power.