Strange chiral nucleon form factors - art. no. 045501

We investigate the strange electric and magnetic form factors of the nucleo n in the framework of heavy baryon chiral perturbation theory to third orde r in the chiral expansion. All counterterms can be fixed from data. In part icular, the two unknown singlet couplings can be deduced from the parity-vi olating electron-scattering experiments performed by the SAMPLE and the HAP PEX Collaborations. Within the given uncertainties, our analysis leads to a small and positive electric strangeness radius, [r(E,s)(2)] = (0.05 +/- 0. 09) fm(2). We also deduce the consequences for the upcoming MAMI A4 experim ent. [S0556-2813(99)06109-9].