For \(\psi\) to exist, \(F\) is negative for values of \(x\lt x_z\), this would imply that when two positive charges are brought very close together they would attract each other and stick.
Otherwise the mass of a positive is just the mass of the particle along time \(t_c\) when \(x_z=0\),
\(m_{po}=m\)
and
\(m_{\rho\,e} c^2=m_\rho c^2-\int^{x_a}_{0}{\psi}dx=m_{\rho\,po} c^2-\int^{x_a}_{0}{\psi}dx=m_{\rho\,po} c^2-\int^{2x_z}_{0}{\psi}dx\)
In both cases,
\(m_{\rho\,e}\lt m_{\rho\,po} \)
because
\(x_{z\,po}\lt x_{z\,e}\)
that more of the \(F\) curve associated with a negative charge is negative, than the \(F\) curve associated with a positive charge.
