Isospin breaking exposed in f0(980)- a0(980) mixing

We suggest that mixing between the f0(980) and a0(980), due to their dynamical interaction with the nearby KKbar thresholds, can give rise to a significantly enhanced production rate of a0(980) relative to a2(1320) in pp -> ps (eta pi0) pf as xF -> 0. The peaking of the cross section as phi -> 0 should also occur. We show that such effects are seen in data and deduce that the f0(980) - a0(980) mixing intensity is 8 +/- 3 %.