Study of the a1 (1269) resonance in the γp →π+π+π-n reaction * * Supported by the National Natural Science Foundation of China (11475227, 11735003), and the Youth Innovation Promotion Association CAS (2016367)

Abstract

Within an effective Lagrangian approach and resonance model, we study the and reactions via the -exchange mechanism. For the reaction, we perform a calculation of the differential and total cross-sections by considering the contributions of the intermediate resonance decaying into and then into . Besides, the non-resonance process is also considered. With a lower mass of , the experimental data for the invariant mass distributions can be fairly well reproduced. For the reaction, with the model parameters, the total cross-section is of the order of 10 μb at the photon beam energy ~2.5 GeV. It is expected that the model calculations in this work could be tested by future experiments.