Energy Conservation - Understand Mass & Reactions

[r3za]

Hi,

I had a question about reactions. I actually know how the baryon number, the lepton number, and the electric charge conservation works for reactions, but what i do not understand is the energy conservation. I searched the whole web for it, but there was no page where I could understand the stuff.

i know that it has something to do with mass, that the mass of a neutron is higher than that of a proton.

For example: p + p > p + n ... i know that the electric charge is not correct, so I need a positron, but then the lepton number is not correct, so i need a ve.

>> p + p > p + n + e+ + ve ... but what about the energy, how can i find out if the energy conservation is oki, and what I have to add to make it work?

It would be really cool if someone could help me out here!

 

[dextercioby]

Conservation of 4momentum in a Feynman diagram (scattering or decay process) is fundamental.

Read pages 72 pp.76 from D.J.Griffiths' "Introduction to elementary particles",Harper & Row,1987.

Daniel.

 

[sir-pinski]

Hi there,

I'm glad to hear that you have a good understanding of the conservation laws for baryon number, lepton number, and electric charge in reactions. As you mentioned, energy conservation is also an important factor in reactions and it is closely related to mass conservation.

In the example you provided, p + p > p + n + e+ + ve, the energy conservation can be checked by using the equation E=mc², where E is energy, m is mass, and c is the speed of light. This equation tells us that mass and energy are equivalent, and therefore must be conserved in reactions.

In this reaction, the mass of the initial particles (two protons) is greater than the mass of the final particles (one proton, one neutron, one positron, and one neutrino). This means that some mass has been converted into energy, which is why you need to add a positron and a neutrino to balance the equation. The energy released from this conversion of mass is what keeps the reaction going and is ultimately conserved.

To check if the energy conservation is correct, you can calculate the total energy of the initial particles and compare it to the total energy of the final particles. If they are equal, then energy conservation is satisfied. Keep in mind that the energy in a reaction can take different forms, such as kinetic energy, thermal energy, and electromagnetic energy.

I hope this helps to clarify the role of energy conservation in reactions. If you have any further questions, feel free to ask. Happy learning!