The Theoretical Study Of The Scattering Process γn→π~-p

The study of N and Δ spectra is one of the important topics in hadron physics.With the framework of the chiral quark model,we extracted the properties of the nucleon and the Δ resonance states by studying photoproduction process γn→π^-p.By fitted the differential cross section,beam antisymmetric Σ,recoil proton polarization P and target particle antisymmetric T experimental data ofγn→π^-p scattering process,we find that:（1）、The resonance stateΔ（1232）has a significant contribution in theγn→π^-p process,and the mass and width of theΔ（1232）are M（?）1220Me V and Γ（?）100Me V,respectively,Which are close to the values determined by PDG.At the same time,we extracted the Δ（1232）Nπcoupling strength C_r（1232）（?）2.3,which is about 1.5 times larger than the coupling constant of the traditional quark model.（2）、N（1535）also plays a very important role in this process.We also get the mass and width of the state N（1535）,M（?）1515Me V and Γ（?）115Me V,respectively.In addition,the Δ（1535）Nπcoupling constant we extracted is about 1.6 times larger than the coupling strength given by the traditional quark model.At the same time,in theγn→π^-p scattering process,we find that the resonance state N（1520）also has a non-negligible effect,and with the energy increases,N（1535）S₁₁and N（1520）D₁₃have a strong interference destructive effect in a relatively high energy region.（3）、In this process,s channel,u channel,t channel,and background items of contact items also play a pivotal role.It is worth mentioning that in our predicted total cross-section,we found that there is two obvious structures nearΔ（1232）andΔ（1535）Nπ,and its main contribution is the resonance statesΔ（1232）and N（1535）,respectively.