Sixty Symbols asked a bunch of physicists what would happen if you placed your hand in the particle beam at the LHC. They didn't know the answer to that so they went digging.
The LHC's beam is focussed down to a tiny spot, less than 1 millimeter across. Also, it contains as much energy as an aircraft transporter in motion. From "I don't know" to "dude you're going to lose your hand for sure" I guess I'm going ahead with the latter.
But check out the video below, because physicists make it sound so much smarter than what I just said.