The Student Room Group
Competition - post a photo you've taken of nature >>
Competition - post a photo you've taken of nature >>
Competition - post a photo you've taken of nature >>

Annihilation of two particles / Rest mass energy

When two particles annihilate (e.g. proton and antiproton), the resulting radiation will have a minimum energy of the sum of the rest mass energies of the two particles, right? But how does the kinetic energy of the particles factor in? Does the energy of the resulting radiation, or in this case, photons, equal the rest mass energies of the proton and antiproton PLUS the the kinetic energies of both particles?

Like this:

hfmin = E0 + KE

?!
Reply 1
Avatar for Morbo
Morbo
17
Original post by laughingbagel
When two particles annihilate (e.g. proton and antiproton), the resulting radiation will have a minimum energy of the sum of the rest mass energies of the two particles, right? But how does the kinetic energy of the particles factor in? Does the energy of the resulting radiation, or in this case, photons, equal the rest mass energies of the proton and antiproton PLUS the the kinetic energies of both particles?

Like this:

hfmin = E0 + KE

?!


Yeah, that's almost right, except you just haven't written algebraically what you described. For particle-antiparticle annhilation, you meant:

hfmin=2E0\text{h}f_{\text{min}} = 2E_0 - minimum photon energy is the sum of the rest mass energies (where each has rest mass energy E0E_0).

but

hf=2E0+KE\text{h}f = 2E_0 + \text{KE} - actual photon energy is the rest mass, plus whatever KE they were carrying when they annhilated.
(edited 13 years ago)
Unless of course the proton and anti proton are virtual pairs, and one of them has negitive energy... :redface:
Reply 3
Avatar for Calrik
Calrik
Original post by QuantumOverlord
Unless of course the proton and anti proton are virtual pairs, and one of them has negitive energy... :redface:


Negative energy what does that even mean. :biggrin:
Reply 4
Avatar for mf2004
mf2004
14
Side note:
When dealing with an annihilation you will always end up with at least 2 photons. The reason is that momentum is conserved, photons have momentum and in the 0 momentum frame momentum is 0 => you need at least 2 photons
Original post by mf2004
Side note:
When dealing with an annihilation you will always end up with at least 2 photons. The reason is that momentum is conserved, photons have momentum and in the 0 momentum frame momentum is 0 => you need at least 2 photons


I love your signiture.

Quick Reply

Related discussions

Latest

Trending

Trending

Articles for you