Strange quark mass from Finite Energy QCD sum rules to five loops

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The strange quark mass is determined from a new QCD Finite Energy Sum Rule (FESR) optimized to reduce considerably the systematic uncertainties arising from the hadronic resonance sector. As a result, the main uncertainty in this determination is due to the value of ΛQCD. The correlator of axial-vector divergences is used in perturbative QCD to five-loop order, including quark and gluon condensate contributions, in the framework of both Fixed Order (FOPT), and Contour Improved Perturbation Theory (CIPT). The latter exhibits very good convergence, leading to a remarkably stable result in the very wide range s₀ = 1.0 - 4.0 GeV², where s₀ is the radius of the integration contour in the complex energy (squared) plane. The value of the strange quark mass in this framework at a scale of 2 GeV is mₛ(2 GeV) = 95 ± 5 (111 ± 6) MeV for ΛQCD = 420 (330) MeV, respectively.