Charge densities of the neutron and proton

Phys Rev Lett. 2007 Sep 14;99(11):112001. doi: 10.1103/PhysRevLett.99.112001. Epub 2007 Sep 13.

Abstract

A model-independent analysis of the infinite-momentum-frame charge density of partons in the transverse plane is presented for the nucleon. We find that the neutron-parton charge density is negative at the center, so that the square of the transverse charge radius is positive, in contrast with many expectations. Additionally, the proton's central d quark charge density is larger than that of the u quark by about 30%. The proton (neutron) charge density has a long range positively (negatively) charged component.