How do I write a nuclear equation for the annihilation of a positron?

[v_pino]

How do I write a nuclear equation representing the annihilation of a positron with an electron?

Do they just cancel out? or do I write energy on the left hand side of the equation?

 

[Jakell]

When an electron and a positron annihilate each other, they produce a pair of photons. The photons conserve energy, and by having two of them, they conserve the momentum of the initial particles as well.

 

[mathman]

When you work in the center of mass sytem, you will get a pair of 511 kev photons going off in opposite directions - the direction is otherwise free.