Unraveling duality violations in hadronic tau decays

Abstract

There are some indications from recent determinations of the strong coupling constant ${\ensuremath{\alpha}}_{s}$ and the gluon condensate that the operator product expansion may not be accurate enough to describe nonperturbative effects in hadronic tau decays. This breakdown of the operator product expansion is usually referred to as being due to ``duality violations.'' With the help of a physically motivated model, we investigate these duality violations. Based on this model, we argue how they may introduce a non-negligible systematic error in the current analysis, which employs finite-energy sum rules with pinched weights. In particular, this systematic effect might affect the precision determination of ${\ensuremath{\alpha}}_{s}$ from tau decays. With a view to a possible future application to real data, we present an alternative method for determining the operator product expansion coefficients that might help with estimating, and possibly even reducing, this systematic error.