Dispersive Techniques for ${\alpha }_s$, $R_{had}$ and Instability of the Perturbative Vacuum

Y. Srivastava, S. Pacetti, G. Pancheri +1

Recent dispersive techniques developed by us are applied to discuss three problems: 1. A long standing discrepan-cy between the measurements of $R(s)$ for $\sqrt{s}=(5÷7.5)GeV$ b…