Nothing happens obviously, [as cosmic rays][1] continuously impinge on us and some have the energies of the LHC. At the cellular level DNA can be damaged and mutations in cells might occur. If it happens to be an ovum or a sperm then something drastic may happen to the putative  embryo coming from a damaged cell. General living organisms have developed repair mechanisms that limit most damage from single cell/particle encounters.

Accelerator beams though with the high number of particles can be killing . [This is the story][2] of a survivor with a  beam encounter.


  [1]: http://en.wikipedia.org/wiki/Cosmic_ray
  [2]: http://en.wikipedia.org/wiki/Anatoli_Bugorski