Lower and upper bounds on the mass of light quark-antiquark scalar   resonance in the SVZ sum rules
  The calculation of the mass of light scalar isosinglet meson within the Shifman-Vainshtein-Zakharov (SVZ) sum rules is revisited. We develop simple analytical methods for estimation of hadron masses in the SVZ approach and try to reveal the origin of their numerical values. The calculations of hadron parameters in the SVZ sum rules are known to be heavily based on a choice of the perturbative threshold. This choice requires some important ad hoc information. We show analytically that the scalar mass under consideration has a lower and upper bound which are independent of this choice: $0.78\lesssim m_s\lesssim1.28$ GeV. 
S. S. Afonin
hep-ph hep-th nucl-th