Question about conservation of lepton and baryon

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SUMMARY

The conservation of lepton and baryon numbers are empirical laws stating that the number of leptons and baryons remains constant in any physical process, such as decay or collisions. For instance, during neutron decay, a neutron transforms into a proton (a baryon) and a pair of leptons, adhering to these conservation laws. This principle does not imply conservation of mass, as demonstrated in the reaction e+ + e- → 2γ, where lepton number is conserved while mass is converted to energy, aligning with the mass-energy equivalence principle E=mc2.

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kelvin490
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I would like to ask what is mean by conservation of lepton and baryon? Does this imply conservation of mass? In addition, does this theory contradicts mass-energy conversion E=mc2?
 
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Both lepton-number conservation and baryon-number conservation are empirical laws. This means that in any process (decay, collisions, etc.) the number of leptons (3 kinds) AND the number of baryons cannot change (similar to charge conservation). So when a neutron decays, it has to decay into another baryon (proton) AND a pair of leptons (including energy conservation requirements). So the question might be "why doesn't the proton decay into mesons and leptons?" Many searches have been made for proton decay into mesons and leptons. My Particle Data Group book
http://pdg.lbl.gov/2009/tables/contents_tables.html
shows that the proton decay lifetime is presently over 1032 years.
Bob S
 
kelvin490 said:
Does this imply conservation of mass? In addition, does this theory contradicts mass-energy conversion E=mc2?

No. For example, in the reaction [itex]e^+ + e^- \rightarrow 2\gamma[/itex], lepton number is conserved (0=0), but mass is not.

kelvin490 said:
In addition, does this theory contradicts mass-energy conversion E=mc2?

No. In the same reaction, mass is converted to energy.
 

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