Study of the decay phi -> f(0)(980)gamma -> pi (+) pi(-) gamma with the KLOE detector

We measured, with the KLOE detector, the spectrum of pi(+)pi(-) invariant mass in a sample of 6.7 x 10(5) e(+)e(-) -> pi(+)pi(-)gamma events with the photon at large polar angle (theta(gamma) > 45 degrees) at a centre of mass energy root s around the phi mass. We observe in this spectrum a clear contribution from the intermediate process phi -> f(0)(980)gamma. A sizeable effect is also observed in the distribution of the pion forward-backward asymmetry. We use different theoretical models to fit the spectrum and we determine the to mass and coupling constants to the phi, to pi(+)pi(-) and to KK. (c) 2006 Elsevier B.V. All rights reserved.