New Precision Limit on the Strange Vector Form Factors of the Proton (The HAPPEX Collaboration)

It has long been established that a complete character-ization of nucleon substructure must go beyond three va-lence quarks and include the qq sea and gluons. In deepinelastic scattering, for example, sea quarks are knownto dominate interactions in certain kinematic regimes.With the discovery by the EMC collaboration [1] thatquark spins are not the dominant contribution to nucleonspin, the role of sea quarks, and especially strange quarks,has been scrutinized. More generally, since valence-quarkmasses account for only about 1% of the nucleon mass, abetter understanding of the role of gluons and sea quarksin nucleon substructure is imperative. Cleanly isolatingthe e ects of the quark sea is typically dicult; one no-table exception is the extraction of the vector strange ma-trix elements hs