Article révisé par les pairs
Résumé : A search for contributions to the reaction ep → eπ0N* from photon-odderon fusion in the photoproduction regime at HERA is reported, at an average photon-proton centre-of-mass energy (W) = 215 GeV. The measurement proceeds via detection of the π0 decay photons, a leading neutron from the N* decay, and the scattered electron. No π0 signal is observed and an upper limit on the cross section for the photon-odderon fusion process of σ(γp → π0N*) < 49 nb at the 95% confidence level is derived, integrated over the experimentally accessible range of the squared four-momentum transfer at the nucleon vertex 0.02 <