Nucleon to delta electromagnetic transition form factors in lattice QCD

Abstract

The electromagnetic nucleon to Δ transition form factors are evaluated using two degenerate flavors of dynamical Wilson fermions and using dynamical sea staggered fermions with domain-wall valence quarks. The two subdominant quadrupole form factors are evaluated for the first time in full QCD to sufficient accuracy to exclude a zero value, which is taken as a signal for deformation in the nucleon-Δ system. For the Coulomb quadrupole form factor the unquenched results begin to deviate from the quenched results at low q2 indicating that dynamical lattice results are closer to experiment. This can be taken as a first confirmation of the expected importance of pion cloud contributions on this quantity. © 2008 The American Physical Society.