# Mater Annihilation -matter v.s. anti-matter-

1. Dec 2, 2006

### taylaron

Mater Annihilation --matter v.s. anti-matter--

hey all,
in the study of "massless particles" such as the electron and the and the positron. in beta decay (beta plus) there is an emission of a subatomic particle called the positron (the anti-particle of the electron)
my thought is that when this decay occurs, why isnt there a mass release of energy. becuase i learned that when matter and anti-matter meet, they annihilate eachother while producing a massive release of energy.
or is it because they "blink" out of existance before it gets in contact with matter? ( doesnt that conflict with the theory "matter can not be created nor distroyed, only transformed.")?

and in an atomic nuclei, when a proton turns directly into a neutron, where does that charge (+) charge go?:surprised

i am aware this might come across as a stupid question

2. Dec 3, 2006

### Parlyne

It's not particularly relevant to this discussion; but, the electron and positron are not massless. Each has a mass of about $$9.11 \times 10^{-31}\ \mathrm{kg}$$. In performing calculations in nuclear or particle physics, it's often useful to treat electrons as massless; but, this only works because all the other energy scales being considered in such a problem are generally much larger than $$m_e c^2$$.

Annihilation can only happen between a particle and its anti-particle. So, if a positron is created, it can only be annihilated by interacting with an electron. And, in fact, this will generally happen. In that case, we can detect the light emitted.

Conservation of mass is, quite simply not true. What is true is the more general conservation of energy. Mass is a form of energy; and that energy can be converted into different forms. But, energy overall will be conserved.

For a proton to change to a neutron, one of two things must happen. Either it must absorb an electron (with negative charge) and emit a neutrino, or it must emit a positron and a neutrino.

3. Dec 3, 2006