i recently saw in my physics textbook a diagram of a positron and a electron being created in pair production. The diagram showed that as soon they where created, they moved in opposite directions and then they spiralled inwards a bit. Now i think the reason why they move in opposite directions is because of the magnetic field, however, if that is the case they why do they then spiral inwards? surely if it is the magnetic field, then shouldn't the electron and positron keep going in opposite directions and not be curling inwards?. Any help would be appreciated.