Electromagnetic form factors of spin-⅓ baryons

Relationships are established among current matrix elements, covariant vertex functions, and multipole form-factor decompositions for the case of electromagnetic interactions of spin-⅓ systems. The electromagnetic current matrix element for spin-⅓ baryons is defined in terms of the minimum required four independent covariant vertex functions. Explicit Lorentz-invariant relations for the multipole form factors are derived in terms of the previously defined covariant vertex function coefficients. The derivation does not involve any nonrelativistic approximations. Finally, the multipole form factors are isolated and expressed in terms of the electromagnetic current matrix elements. These results are particularly useful in lattice QCD calculations.