S-wave γγ\to ππand f_0(980)\to ππ

Abstract

We report on a dispersion relation for the γγ\to (ππ)_I S-wave in isospin I emphasizing the low energy region. The f_0(980) signal that emerges in γγ\to ππis also discussed. Our results could be used to distinguish between different ππisoscalar S-wave parameterizations. We also calculate the width of the σresonance to γγand obtain the value Γ(σ\toγγ)=(1.68\pm 0.15) KeV. Finally, we elaborate on the size of the f_0(980) coupling to ππand show that its smallness compared to the K\bar{K} one is not related to the OZI rule.

6 pages, 1 figure. Prepared for the Workshop on Scalar Mesons and Related Topics, Lisbon, 11-16 Feburary 2008