My work is indirectly related to proton beams. Your comment about energy deposition in human tissue reminded me they can be used for cancer treatment that's loc

My work is indirectly related to proton beams. Your comment about energy deposition in human tissue reminded me they can be used for cancer treatment that's localised to a certain depth. In fact http://en.wikipedia.org/wiki/Proton_Beam_Therapy http://en.wikipedia.org/wiki/Proton_Beam_Therapy would go some way to answering the original question about the interaction between the LHC beam and a human hand. Presumably we can take it as given that there is some sort of exit window (not sure what material would be best?) from the beam guide into the air. Aside from the bremstrahlung, proton beam interactions with matter include spallation from heavy nuclei (giving neutrons) and the formation of muons. Both of these would deviate from the original proton beam direction and irradiate other parts of the body.