Isospin breaking exposed in f(0)(980)-a(0)(980) mixing

We suggest that mixing between the F-0(980) and a(0)(980), due to their dyn amical interaction with the nearby K (K) over bar thresholds, can give rise to a significantly enhanced production rate of a,(980) relative to a(2)(13 20) in pp ->, p(s)(eta pi degrees)p(f) as x(F) -> 0. The peaking of the cro ss section as phi -> 0 should also occur. We show that such effects are see n in data and deduce that the f(0)(980) - a(0)(980) mixing intensity is 8 /- 3 %. (C) 2000 Elsevier Science B.V. All rights reserved.