Study of the decay phi--> f0(980)g --> pi+pi-g with the KLOE detector

TL;DR

This study measures the pi+pi- invariant mass spectrum in phi decays using the KLOE detector, revealing the phi --> f0(980)g process and extracting the f0(980) properties through spectral fitting.

Contribution

It provides detailed experimental data on phi decays involving f0(980), and compares different theoretical models to determine the f0(980) mass and couplings.

Findings

Clear contribution from phi --> f0(980)g observed.

Determined f0(980) mass and coupling constants.

Observed effects in forward-backward asymmetry distribution.

Abstract

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-g events with the photon at large polar angle (theta_g>45^o) at a centre of mass energy sqrt(s) around the phi mass. We observe a clear contribution from the intermediate process phi --> f0(980)g. A sizeable effect is also observed in the distribution of the forward-backeard asymmetry. We use different theoretical models to fit the spectrum and we determine the f_0 mass and coupling constants to the phi, to pi+pi- and to KK.