The proton shrinks in size : Nature News: "'Something is missing, this is very clear,' agrees Carl Carlson, a theoretical physicist at the College of William & Mary in Williamsburg, Virginia. The most intriguing possibility is that previously undetected particles are changing the interaction of the muon and the proton. Such particles could be the 'superpartners' of existing particles, as predicted by a theory known as supersymmetry, which seeks to unite all of the fundamental forces of physics, except gravity.
But, Carlson says, 'the first thing is to go through the existing calculations with a fine tooth comb'. It could be that an error was made, or that approximations made in existing quantum calculation simply aren't good enough. 'Right now, I'd put my money on some other correction,' he says. 'It's also where my research time will be going over the next month.'"