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

The study of the charge asymmetry of produced particles allows to investigatethe interference of different production mechanisms and to determine newfeatures of the corresponding amplitudes. In the process $e^- e^+ \to e^- e^+\pi^+ \pi^-$ the two-pion system is produced via two mechanisms: two-photon(C-even state) and bremsstrahlung (C-odd state) production. We study the chargeasymmetry of pions in a differential in the pion momenta cross sectionoriginating from an interference between these two mechanisms. At low effectivemass of dipions this asymmetry is directly related to the s- and p-phases ofelastic $\pi\pi$ scattering. At higher energies it can give new informationabout the $f_0$ meson family, $f_2(1270)$ meson, etc. The asymmetry isexpressed via the pion form factor $F_\pi$ and helicity amplitudes $M_{ab}$ forthe subprocess $\gamma^*\gamma\to \pi^+\pi^-$ as $\sum G_{ab}{\rmRe}(F_\pi^*M_{ab})$ where we have calculated analytically the coefficients$G_{ab}$ for the region giving the main contribution to the effect. Severaldistributions of pions are presented performing a numerical analysis in a modelwith point-like pions. In the region near the dipion threshold the asymmetry isof the order of 1%. We show that with suitable cuts the signal to backgroundratio can be increased up to about 10%.Comment: 16 pages, 10 figures, LaTeX, style files for EPJC include

Charge asymmetry of pions in the process $e^-e^+\to e^-e^+\pi^+\pi^-$