Study (using a chiral effective Lagrangian model) of the scalar and pseudoscalar meson mass spectrum of QCD at finite temperature, above $T_c$

Abstract

In this work, we analyze (using a chiral effective Lagrangian model) the scalar and pseudoscalar meson mass spectrum of QCD at finite temperature, above the chiral transition at $T_c$, in the realistic case with $N_f=2+1$ light quark flavors (that is, with $m_{u,d}\to 0$ and $m_s\ne 0$), looking, in particular, for signatures of the breaking of the $U(1)$ axial symmetry above $T_c$. A critical comparison with the corresponding results obtained (in a previous study) in the two limit cases $N_f=2$ and $N_f=3$ and with the available lattice results is performed, together with a discussion on the limits of validity of a description in terms of a chiral effective Lagrangian model.

Comments: 14 pages; some misprints have been corrected and new comments have been added in the conclusions