Mesonic fluctuations in a nonlocal Nambu–Jona-Lasinio model

Plant, R. S. and Birse, M. C. (2002) Mesonic fluctuations in a nonlocal Nambu–Jona-Lasinio model. Nuclear Physics A, 703 (3-4). pp. 717-744. ISSN 0375-9474 doi: 10.1016/S0375-9474(01)01669-4

Abstract/Summary

The effects of meson fluctuations are studied in a nonlocal generalization of the Nambu–Jona-Lasinio model, by including terms of next-to-leading order (NLO) in 1/Nc. In the model with only scalar and pseudoscalar interactions NLO contributions to the quark condensate are found to be very small. This is a result of cancellation between virtual mesons and Fock terms, which occurs for the parameter sets of most interest. In the quark self-energy, similar cancellations arise in the tadpole diagrams, although not in other NLO pieces which contribute at the 25% level. The effects on pion properties are also found to be small. NLO contributions from real pi-pi intermediate states increase the sigma meson mass by 30%. In an extended model with vector and axial interactions, there are indications that NLO effects could be larger.