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 Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

We derive the amplitude for the process $e^+e^-\to \pi^0\pi^0$ at largeinvariant energy. The process goes through the two-photon exchange and itsamplitude is expressed in terms of the convolution integral which depends onthe shape of the pion distribution amplitude (DA) and the centre of massscattering angle. Remarkable feature of the integral is that it is verysensitive to the end-point behaviour of the pion DA -- it starts to diverge ifpion DA nullifies at the end-point as $\sqrt x$ or slower. That makes the$e^+e^-\to \pi^0\pi^0$ process unique probe of the shape of the meson DAs. Theestimated cross section is rather small, for $\sqrt s = 3$ GeV it ranges from afraction of femtobarn (for the asymptotic DA) to couple of femtobarn (for theChernyak-Zhitnitsky DA). The observation of the process $e^+e^-\to\pi^0\pi^0$with the cross section higher as estimated here would imply very unusual formof the pion DA, e.g. the flat one. The derived amplitude can be easilygeneralized to other processes like $e^+e^-\to \sigma\sigma, K_SK_S, \eta\eta,\eta^\prime\eta, \pi^0 f_2$, etc.

A novel way to probe distribution amplitudes of neutral mesons in e^+e^- annihilation