RT Journal Article T1 Role of the thermal f_0(500) in chiral symmetry restoration A1 Ferreres Solé, S. A1 Gómez Nicola, Ángel A1 Vioque Rodríguez, A. AB We show that the sigma/f_0(500) state with finite-temperature T corrections to its spectral properties included plays an essential role for the description of the scalar susceptibility chi_S, signaling chiral symmetry restoration. First, we use the O_4 linear sigma model as a test bed to derive the connection between chi_S and the sigma propagator and to check the validity and reliability of the approach where chi_S is saturated by the sigma/f_0(500) inverse self-energy, which we calculate at finite T to one loop. A more accurate phenomenological description is achieved by considering the saturation approach as given by the thermal f_0(500) state generated in unitarized chiral perturbation theory (UChPT). Such an approach allows us to describe fairly well recent lattice data within the uncertainty range given by the UChPT parameters. Finally, we compare the UChPT saturated description with one based on the hadron resonance gas, for which the hadron mass dependences are extracted from recent theoretical analysis. Several fits to lattice data are performed and confirm the validity of the thermal f(0)(500) saturated approach and hence the importance of that thermal state for chiral symmetry restoration. PB American Physical Society SN 2470-0010 YR 2019 FD 2019-02-26 LK https://hdl.handle.net/20.500.14352/13244 UL https://hdl.handle.net/20.500.14352/13244 LA eng NO ©2019 American Physical Society We are very grateful to J. Ruiz de Elvira and J. Sanz-Cillero for useful comments and discussions. Work partially supported by research Contract No. FPA2016-75654-C2-2-P (Spanish "Ministerio de Economia y Competitividad"). NO Ministerio de Economía y Competitividad (MINECO) DS Docta Complutense RD 28 abr 2024