English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

From recent analysis of the $\pi\pi$ scattering amplitude, it has beenclaimed that there exists a broad and light $\sigma$ meson. However, if thismeson really exists, it must also appear in other observables such as the pionscalar form factor. With the use of unitarity and dispersion relations togetherwith chiral perturbation theory, this form factor is analyzed in the complexenergy plane. The result agrees well with the empirical information in theelastic region and reveals a resonance pole at $\sqrt{s}=445-i235$ MeV. Thisgives further strong evidence for the existence of the $\sigma$ meson.Comment: 6 pages, 3 figs, REVTeX, to appear in Phys. Rev.

Pion scalar form factor and the sigma meson