Mesonic modes in a confining model at finite temperature

The mass spectrum of pseudoscalar and scalar mesons at finite temperature is studied within a nonlocal quark model with Polyakov loop extension. The analysis is performed in the leading order of the 1 / N c expansion. To suppress unphysical quark production thresholds in meson polarization loops in the hadronic phase, the quark propagator is modified after the inverse Laplace transform. In the deconfined phase, the quark pole is treated separately, while the same modification applies to the remaining part. For a consistent description of both confining and deconfining phases, an adjustment of the transformed propagator is proposed. At finite temperature, Lorentz symmetry breaking leads to the splitting of meson modes. The screening masses are computed over a wide temperature range, and the pole masses up to the deconfinement transition. The results are compared with lattice QCD data and show reasonable agreement.