CP-Nonconserving Parameter and theπ+−π0Electromagnetic Mass Difference

Abstract

An elementary calculation with Feynman graphs is used as a device for reproducing the ${\pi }^{+}-{\pi }^0$ electromagnetic mass shift. Further use of this device makes possible a hypothetical calculation of the $\mathrm{CP}$-nonconserving parameter $\left|〈K_L\right|K_S〉\left|\cong \right|2\mathrm{}\mathrm{Re}\epsilon |$ which yields the result $\left|2\mathrm{}\mathrm{Re}\epsilon \right|\approx \frac{\delta \left({m_{\pi }}^2\right)}{2{m_{\rho }}^2}=\left(\frac{\delta m_{\pi }}{m_{\pi }}\right){\left(\frac{m_{\pi }}{m_{\rho }}\right)}^2\cong 1.2\times {10}^{-3\mathrm{}}$.