Much likely, nothing at all! The more energy a particle gets, the smaller the probability of interacting with anything. And if it does interact in your head...

Much likely, nothing at all! The more energy a particle gets, the smaller the probability of interacting with anything. And if it does interact in your head... nothing at all! At such an energy, it is so tiny that at most one electron or one nucleon (i.e. proton or neutron) will get the thrill of its life and find itself leaving precipitously your body in order to smash, a few nanoseconds later, into the planet behind you. You won't notice, and the Earth won't either.