The features of the Resonance Chiral Theory (RχT) related to the description of the lightest scalar resonances, σ , f 0 (980) and a 0 (980), are discussed. Major attention is paid to the fits of the invariant mass distributions in the radiative decays of the φ (1020) meson (φ → (γa 0 →)γπη and φ → (γ f 0 /σ →)γππ). The study of the scalar sector in RχT is motivated by the success of the theory predictive power in numerous processes with other types of resonances. We conclude that RχT is sufficiently flexible to describe these decays, however the further quantitative improvement is required. The technical work-outs and related important questions are outlined.

The low mass of D * s0 (2317) presents problems for the conventional quark model, leading to consideration of other options regarding a multi-quark system. Here, we investigate the scalar open-charm state D * s0 (2317) and its bottom partner by the Thermal QCD Sum Rules (TQCDSR) method using the two-point correlation function with contributions of the nonperturbative condensates up to dimension six. Our calculations indicate that the variations in mass and decay constant values are stable through temperatures up to T ∼ = 100 MeV and fall after this point. At the critical temperature, the values of mass and decay constant change up to 94%, 71% of their values in vacuum in the molecular scenario, and 94%, 75% in the diquark-antidiquark scenario. Besides, we find more dramatic changes in mass and decay constant above T c , and hence we interpret it as the hadrons starting to disappear. Also, the detailed search for hot medium effects on the hadronic parameters of open-charm meson D * s0 (2317) and the bottom partner may have implications for the QCD phase diagram derived from heavy-ion collision experiments. Finally, these results may help distinguish conventional quark model mesons from exotic states.