Charged-current shift in neutrino-electron scattering ($(c_V,c_A)\mapsto (c_V+1,c_A+1)$)

Electron-neutrino scattering has a charged-current contribution absent for muon neutrinos. Fierz rearrangement combined with the external fermionic sign adds a left-electron current: $c_V\to c_V+1$, $c_A\to c_A+1$. The right-electron coupling stays unchanged; the left-electron coupling increases by two.