The γp → na2+ (1320) → nρ0π+ reactions within an effective Lagrangian approach

We investigate the tensor meson a2(1320) photon-production off proton in the γp → na2+ (1320) and γp → nρ0π+ reactions within the effective Lagrangian approach and isobar model. For γp → na2+ (1320) reaction, by considering the contributions from only the t-channel π+ exchange, we get a fairly good description of the current experimental data for the total cross-section. Based on the theoretical results of the γp → na2+ (1320) reaction, we studied the role of a2(1320) meson in the γp → nρ0π+ reaction, which mainly contributes to the γp → nπ+π+π- reaction. The latter reaction has been measured by the CLAS Collaboration at the photon energy Eγ around 5.1 GeV. For the γp → nρ0π+ reaction, we pay attention to the low photon energy region where the contribution from a2(1320) meson is dominant, while the contribution from the π2(1670) meson could be very small and hence can be neglected. The total cross-sections, invariant mass distribution and the Dalitz plot of γp → nρ0π+ reaction are shown, which can be tested by future experiments. (author)