Charge “asymmetry” from the isospin symmetry in $pp\to pp\pi^ + \pi^-$

Abstract.

Charge “asymmetry” meant as $\sigma_{ + -} = {\mathrm d} \sigma/{\mathrm d} M_{p\pi^ + }- {\mathrm d} \sigma/{\mathrm d} M_{p\pi^-}$ is easy to reproduce by the simple-minded reaction mechanism, which stems on the interference of $\Delta^{ + + }$ and $\Delta^{0}$ excited in one of the colliding protons. High-quality experimental data for the $pp\to pp\pi^ + \pi^-$ reaction taken at CELSIUS storage ring with the PROMICE/WASA detector can be described by the Lorentz-invariant phenomenological approach. The same approach is applied for the description of the asymmetry between $M_{pp\pi^ + }$ and $M_{pp\pi^-}$ invariant-mass spectra.