Study of the a1（1260） resonance in the γp→π+π+π-n reaction

Within an effective Lagrangian approach and resonance model, we study the γp→α1(1260)+n andγp→π^+π^+π^-n reactions via the π-exchange mechanism. For the γp→π^+π^+π^-n reaction, we perform a calculation of the differential and total cross-sections by considering the contributions of the α1(1260) intermediate resonance decaying into per and then into π^+π^+π^-. Besides,the non-resonance process is also considered. With a lower mass of α1(1260), the experimental data for the invariant π^+π^+π^-mass distributions can be fairly well reproduced. For theγp→α1(1260^+n reaction, with the model parameters, the total cross-section is of the order of 10 μb at the photon beam energy Eγ2.5 GeV. It is expected that the model calculations in this work could be tested by future experiments.