Basis Light-front Quantization Approach To Positronium

Basis Light-front Quantization(BLFQ)has been developed as a nonperturbative framework for solving quantum field theories.We apply this approach to Quantum Elec-trodynamics(QED)at strong couplings and use the positronium system as a test case.Within the BLFQ framework,we use the light-front Hamiltonian of QED as the input.We work with the truncated Fock space which includes the |e+e->and |e+e-?>Fock sec-tors.Since the photon degree of freedom generates the fermion self-energy correction,we develop a basis dependent nonperturbative mass renormalization scheme to handle the divergence caused by the fermion self-energy correction.By solving the eigenequa-tion of the light-front Hamiltonian,we obtain the mass spectrum and corresponding light-front wave functions of the positronium system.The obtained ground state bind-ing energy is close to the prediction from nonrelativistic quantum mechanics.From the obtained mass spectrum,we find that the rotational symmetry is restoring as the basis size increases.The mass spectrum of the positronium system at various coupling con-stants all show the trend of convergence with respect to the basis truncation parameters.The corresponding light-front wave functions encode all the information of the bound state structure.Our wave functions in the |e+e->Fock sector reasonably agree with the ones from the previous approach based on an effective one-photon-exchange interac-tion.We calculate the photon distribution function,charge radius and decay constant of the positronium from the obtained light-front wave function.