The Study Of Baryon Spectrum At BESⅢ And Fast Simulation At CEPC

Quantum Chromodynamics (QCD) is the elementary theory of the strong interactions. So far, all the hadrons consist of three or two quarks. However QCD theory allows existence of new types hadrons including hybrids, glueballs and multi-quark states.Searching for new types of hadrons in experiments is important to develop QCD. J/Ψ decays is regarded as an ideal laboratory for studying new types of hardons. Based on the high statistic data sample taken on BESIII, it is very convient for us to study the hadron physics.N*(1535) is known as nucleon with the spin-parity of1/2-. It may have a multi-quark component in theoretical interpretation, i.e., maybe it is possible to be the new type hadron beyond the quark model. So it is important to study N*(1535). Based on106M Ψ(2S) samples and225M J/Ψ samples collected with the BESIII detector, we study the N*(1535) production with the decay modes of N*(1535)�'KA and N*(1535)�'π pn in Ψ(2S)�'pKA+c.c. and J/Ψ�'ppππ in this paper.Feynman Diagram Calculation (FDC) Partial Wave Analysis is performed in Ψ(2S)�'pKA+c.c. to study the intermediate resonances. The best solution includes nine resonances:N(1710)、 A(1570)、 A(1600)、 A(1690)、 A(1820)、K(2075) and K2(2250). All the significances of resonances are large than5a. The mass、 width and Jp are measured to be:The results are not consistent with BESⅡ measurements,At present, FDC is also performed in J/Ψ�'pKA+c.c. We may confirm the results with J/Ψ decay.In the analysis of J/Ψ�'ppππ, there are two narrow peaks on mass spectra of Mpπ-and Mpπ+. Through fitting mass spectra, we use flatte formula to describe the N*(1535) for the first time at BESIII. The fitting results areBecause of the complex backgrounds, it is need further study for accurate measurements.There is another important work in this paper. We perform the simulation and analysis at the future Circular Electron Positron Collider (CEPC). Based on the tools from International Linear Collider (ILC), we generate the samples of single particles at different detector geometries and different energies. Using the full simulation of single particles, we establish the fast simulation.In fast simulation, we measure the Higgs recoil mass and production cross section in e+e-�'ZH�'μμM. We investigate the expected measurement accuracy at different radius of TPC.With an integration luminosity of500fb-1, in a model independent way without using any information from the Higgs decay final state in the analysis, a mass precision of31MeV is obtained at TPC radius of1808mm. In a model dependent analysis, the mass precision is improved to26MeV. The corresponding cross section can be measured to a relative precision of4.3%and3.7%. When the TPC radius is reduced to1365mm, the mass measurement accuracy is37MeV and32MeV for the model independent and dependent cases while the cross section is4.6%and4.0%.Thus the mass and total generation cross section can be measured to very high precision at CEPC. When TPC radius is reduced by25%, the results are worse than default. The cost will also be lower. We hope this study will serves as reference for the CEPC detector design.