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Bochao Liu Xi’an Jiaotong University Collaborators: V.Baru, J.Haidenbauer and C.Hanhart.
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Bochao Liu Xi’an Jiaotong University Collaborators: V.Baru, J.Haidenbauer and C.Hanhart
1. In recent years, an effective field theory that can be applied to the reactions NN->NNpi made significant success.However,the calculation of two pion production in NN collisions in the framework of ChPT does not exist yet. Phys. Rept. 397,155(2004) & J.Phys.Conf.Ser.295:012026(2011). 2. In some pioneering works on NN to NNpipi, although chiral symmetry was already implemented, the leading order diagrams are not included completely. 3. This study provides the theoretical basis for a future evaluation of the non-resonant contributions in two-pion production reactions in nucleon-nucleon collisions.
Effective Lagrangian Production operators Be convoluted with NN wave fucntion Amplitudes Phys. Rev. C 49, 2932 (1994)&Phys. Rev. C 53 2086 (1996) &Int. J. Mod. Phys. E 4, 193(1995) Hybrid approach
Expansion parameter : The power counting rules are different compared to the standard ChPT due to the new scales appear in the amplitudes. This helps us to find which diagrams are important. For NN->NNpi near threshold: For NN->NNpipi near threshold: Phys. Rept. 397,155(2004)
The ellipses refer to the NN wave functions. In our work, we use ccf potential(PRC48,2190(1993)) and the extended CDbonn potential(PRC63,024001(2001))
Results: 1.)We identify various diagrams are equally important. CCF CD-Bonn 2.) Diagram e shows rather strong dependence on the employed NN model.
Results: The NN interaction in the initial and intermediate states plays an important role in the calculation. There are sizable interferences between the individual contributions
Solid line: results with using CCF Model Dashed line: results with using CD-Bonn Model Results: • To check the convergence of chiral expansions: • To calculate explicitly subleading contributions • To compare the results from leading-order contributions to experimental observables near threshold The contribution of the non-resonant background near threshold is sizable and should be taken into account in analysis.