Exchange Particles are to show the transfer of (for example) +/- charge to the other side so the charges balance. But I don't understand... Beta plus decay: p → n + e+ + νe. This is just an example, the Feynman diagram shows a W+ boson transferring the positive charge to the right hand side, but in the equation: +1 →0 + (+1) + 0 It's all balanced. So where does the boson come in? Is it to just reinforce the fact that a positron is produced?