Study of the scalar and pseudoscalar meson mass spectrum above the QCD chiral phase transition, using an effective Lagrangian approach

Abstract

In this work, expanding on previous analyses, we employ an effective Lagrangian approach to investigate the mass spectrum of scalar and pseudoscalar mesons at finite temperature, above the (pseudo-)critical temperature $T_c$, in a "realistic" $N_f=2+1$ flavor scenario with degenerate $up$ and $down$ quarks and a heavier $strange$ quark: $0<m_u=m_d\ll m_s$. The model's predictions are then critically compared with available lattice QCD results (where meson screening masses are extracted from chiral susceptibilities, which correspond to two-point correlation functions of suitable interpolating operators), looking, in particular, for signatures of the breaking of the $U(1)$ axial symmetry above $T_c$.

Comments: 36 pages, 8 figures; revised version, published in Eur. Phys. J. A: a misprint in Eq. (3.25) has been corrected and new comments and a relevant reference have been added