# Question about conservation of lepton and baryon

• kelvin490
This theory does not contradict the mass-energy conversion equation. In summary, lepton-number conservation and baryon-number conservation are empirical laws that state that the number of leptons and baryons cannot change in any process. This does not imply conservation of mass, and this theory does not contradict the mass-energy conversion equation.
kelvin490
Gold Member
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?

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 $e^+ + e^- \rightarrow 2\gamma$, lepton number is conserved (0=0), but mass is not.

kelvin490 said:

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

## 1. What is the conservation of lepton and baryon?

The conservation of lepton and baryon is a fundamental principle in particle physics that states that the total number of leptons and baryons in a closed system remains constant over time.

## 2. Why is the conservation of lepton and baryon important?

This principle is important because it helps to explain and predict the behavior of subatomic particles and their interactions. It is also a fundamental aspect of the Standard Model of particle physics.

## 3. How is the conservation of lepton and baryon related to the conservation of energy and momentum?

The conservation of lepton and baryon is related to the conservation of energy and momentum through Noether's theorem, which states that for every symmetry in a physical system, there is a corresponding conservation law. The conservation of lepton and baryon is a result of the symmetries in the laws of physics.

## 4. Can the conservation of lepton and baryon be violated?

According to the Standard Model, the conservation of lepton and baryon is a fundamental principle and cannot be violated. However, there are some theories that suggest it may be possible under certain extreme conditions, such as in the early universe or in high-energy particle collisions.

## 5. How is the conservation of lepton and baryon experimentally verified?

The conservation of lepton and baryon is experimentally verified through a variety of techniques, such as particle accelerators and detectors. By measuring the number and properties of particles before and after interactions, scientists can confirm that the total number of leptons and baryons remains constant.

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