Day 3: The subatomic particle Conservation Laws

Nothing exists except Atoms and Empty Space , Everything else is opinion


                  – Democritus


Today we will talk about the more “complicated” conservation laws .

These laws were discovered after people could make giant accelerators to “make” subatomic particles.


a) Baryon Family Number conservation : The larger/heavier elemantary

   are called baryons . These are protons , sigma , neutron etc.

   These particles are said to have a baryon number of 1 . Their

   antiparticles are said to have a baryon number of -1 . The particles

   that do not come in the baryon family have a baryon number of 0 .


   proton + proton -> proton + sigma + kaon


   is a valid physical phenomenon  because there are 2 baryons on before

   the “reaction” ( 2 protons ) and 2 after it ( proton and sigma ).


   All baryons(except proton) undergo spontaneous disintegration into

   lighter baryons . But the proton is the lightest baryon . So it cannot

   decay into anything . This is a very remarkable thing . The proton

   is a very heavy particle and there are so many particles lighter

   than it . The proton is almost 1837 times the weight of an electron .

   But since it is the lightest baryon it CANNOT decay . It is stable.

   Its enourmous energy is locked in it forever .


   The stability of the proton accounts for the stability of nucleus and

   the reason why atoms , molecules etc are formed and they stay .

   The reason why we have a world .


b) Electron Family number conservation:

   The electron family consists of only 2 particles . The electron and

   its antiparticle the neutrino .

   This number is also conserved .


   neuton -> proton + electron + neutrino


   shows that there are 0 electron family particles on the LHS . And there

   are 0 on the RHS ( because the electron has +1 electron family no

   and the neutrino has -1 electron family no . So they cancel ) . The

   neutron and proton are baryon and have 0 electron family no .


c) Muon Family number :

   There are two particles in this family: muon and its antiparticle .

   And their number is also conserved .


   This completes our list of the 7 conservation laws . In any “reaction”

   / phenomenon all these conservation laws must hold .


   There is another conservation law : The conservation of strangeness.

   Some particles ( called strange particles 🙂 )  have a strangeness

   number and it is partially conserved( conserved only in some processes

   called “strong interactions” ) . We will not cover it here .    


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