On the size of the sigma meson and its nature

Understand

In this work the nature of the \sigma or f_0(600) resonance is discussed by evaluating its quadratic scalar radius, \la r^2\ra_s^\sigma.

• This allows one to have a quantitative estimate for the size of this resonance.
• We obtain that the \sigma resonance is a compact object with $\la r^2\ra_s^\sigma=(0.19\pm0.02)-i(0.06\pm0.02)$ fm^2.
• Within our approach, employing unitary chiral perturbation theory, the \sigma is a dynamically generated resonance that stems from the pion-pion interactions.