Speaker
Description
Transitional pion form factor; 1/Nc corrections; nonlocal quark model
The fundamental theory of strong interactions is quantum chromodynamics. In the low-energy area, the strong coupling constant is not a small parameter, so the use of methods that do not use perturbation theory, for example, effective quark models, is required.
One of such models is the nonlocal quark model [1]. The model is based on expansion in terms of the inverse number of quarks (1/Nc). When considering the diagram technique within the framework of the model, it turns out that any meson propagator in the diagrams leads to a suppression coefficient of 1/Nc [2].
A large number of diagrams with 1/Nc corrections leads to the need to automate the calculation process. The following calculation program is currently implemented:
• The initial stage of generating diagrams is carried out in the QGRAF program [3]
• A program was written for processing data generated by QGRAF, where an algorithm for selecting diagrams by 1/Nc-indices was implemented
• Classification of diagrams into certain types has been made
• Subsequently, the expressions are transferred to the FORM analytical calculation program
Using the program, the transition form factor of the pion was considered [4].
- Radzhabov A.E. SU(2)×SU(2) nonlocal quark model with confinement / Radzhabov A.E., Volkov M.K. // Eur.Phys.J. – 2004. – Vol. 19. – P. 139-144.
- Radzhabov A.E. Nonlocal PNJL model beyond mean field and the QCD phase transition / Radzhabov A.E. [and others] // Phys. Rev. – 2011. – Vol. 83. – 116004.
- Noguera P. QGRAF 3.5.0 / P. Noguera // CeFEMA, Instituto Superior T´ecnico, Universidade de Lisboa (ULisboa), Lisbon, Portugal. – 2021.
- Hoferichter M. Asymptotic behavior of meson transition form factors / Hoferichtera M., Stoffer P. // Journal of High Energy Physics. – 2020.
