At the fundamental level (as depicted in the Feynman diagram on the right), this is caused by the conversion of the negatively charged (− ⁠ 1 / 3 ⁠ e) down quark to the positively charged (+ ⁠ 2 / 3 ⁠ e) up quark by emission of a W boson ; the W boson subsequently decays into an electron and an electron antineutrino: