光生反应γp→π-Δ++中的核子激发态OACSTPCD

The first measured high-precision data on the differential cross sections and polarization observable beam asymmetry ∑ for the γp→π-Δ++reaction from the LEPS collaboration are analyzed within a tree-level effective lagrangian approach.In addition to the t-channel π and ρ exchanges,the u-channel Δ exchange,the s-channel N exchange,and the interaction current that is required by the gauge invariance,the s-channel nucleon resonance exchanges are further taken into account to reproduce the data of LEPS.Numerical results show that,the data on ∑ can not be well reproduced when no contributions from the s-channel resonance exchanges are introduced.Further analyses show that,by including the contribution from the resonance N(1860)5/2+,both the data on the differential cross sections and beam asymmetry ∑ can be well reproduced.