N～*(1535) Excitation And η Production In High-energy Proton-Nucleus Collisions

In this thesis, we investigate theoretically the mechanism ofηmeson productionfor the proton-nucleus reaction p+A→p′+A′+ηin the effective Lagrangianapproach. Due to isospin conservation in strong interaction,Ï€,ρ,σmesons can beexchanged between proton and nucleus with isospin T≠0, while only theσcan beexchanged between proton and nucleus with isospin T=0. By assuming the interme-diate N^*(1535) resonance is excited on the proton incidence and nucleus target, andthen decay intoηmeson and nucleon (N), we calculate the invariant mass distributionof outingηN, Dalitz plots and cross section of the reaction. Takeing ¹⁸0, ¹²C and ⁴Heas target nucleus, we give the the numerical results at the kinetic energies of incom-ing proton below 2.5GeV. In order to help experiment research, we also calculate thedouble differential cross section, the energy and the angle distribution of outgoingηmeson, which is useful to design the experimental detector of hadron near the thresholdenergy of theηproduction. Finally, the nuclear medium effects of N^*(1535) is takeninto account.Dalitz plots show a dense plot region andηN invariant mass distributions have aclear peak around 1510MeV, which indicate the signature of N^*(1535) excitation in re-actions. Total cross section calculations show that it is lager for the T≠0 nucleus thanfor the T=0 nucleus. Especially, the contribution which comes from the N^*(1535)excitation on the target is suppressed for both T≠0 and T=0 nucleus; the domi-nating contribution comes from the N^*(1535) excitation on the proton incidence. For the T≠0 nucleus, the contribution of theρmeson exchange to total cross section ismuch larger than that ofσ- andÏ€-exchange, which indicates theρmeson exchange isimportant for the T≠0 nucleus.At present, there is little experimental data about the interaction information be-tweenηand nucleon or nuclear excitation, so the experiment ofηproduction is veryimportant. The Cooling Storage Ring(CSR) in Lanzou heavy ion collision will be ableto accelerate the proton beam up to 2.8GeV in kinetic energy. The total cross sectionof theηmeson production reactions induced by proton on nuclear targets are in theorder ofμb. Therefor, it is fully possible to investigate the mechanisms of theηme-son production and the properties of N^*(1535) resonance at the CSR. Our investigationprovides some valuable information for the experiment ofηproduction.