Do Electron-Positron Scattering Cross Sections Always Increase with Energy?

[touqra]

I was wondering whether there's any interactions or productions that has cross section that doesn't only increase monotonously with energy, but has a drop somewhere at certain energy scales ?

 

[mathman]

Neutron cross-sections are in general quite irregular when considering interation with various nuclei, especially heavy ones.

Gamma-ray cross sections also have some irregularity (in the kev range) due to certain resonances.

 

[Norman]

check out this link:
http://pdg.lbl.gov/2007/reviews/hadronicrpp.pdf

specifically look at electron-positron scattering.