No, mass is not conserved in particle decay.
The concept of mass conservation, which many may remember from chemistry or introductory physics, is an approximation that only applies to low-energy situations. When dealing with particle decay, the energies involved are substantial enough that mass can transform into other forms of energy, and vice-versa, as defined by Einstein’s mass-energy equivalence (E=mc²).
Understanding Mass Conservation and Particle Decay
| Feature | Mass Conservation | Particle Decay |
|---|---|---|
| Scope | Primarily applies to low-energy events and interactions. | Deals with high-energy processes. |
| Mass Change | Mass remains relatively constant in reactions. | Mass may change significantly as it converts into energy or other particles. |
| Relevant Physics | Classical physics or basic chemistry | Relativistic physics (E=mc²) |
Key Points about Particle Decay and Mass:
- Not a Strict Law: The "law" of conservation of mass is not a fundamental law in high energy physics, but rather an approximation suitable for low-energy chemical reactions.
- Energy-Mass Equivalence: Einstein's famous equation (E=mc²) shows that mass and energy are interchangeable. In particle decay, mass can be converted into energy and kinetic energy of the resulting particles, or energy can be converted into new particles with mass.
- Particle Transformations: In particle decay, the initial particle transforms into new particles with different mass. The total mass of the decay products is not necessarily the same as the mass of the initial particle.
- Example: A heavy particle may decay into lighter particles and energy. The combined mass of the resulting lighter particles may be less than the original particle because some of the original mass has been converted into kinetic energy.
- For instance, consider a hypothetical case: A particle of mass 10 units decays into two particles, each with a mass of 4 units. The remaining 2 units of mass have been converted into the kinetic energy of the resulting particles. The total mass of the decay products is 8 units, not 10.
- This change in mass is directly related to the energy released in the decay.
According to the provided reference:
Mass is not conserved in that decay, but then there is no expectation that it would be. The "law" of conservation of mass is only an approximate rule that applies to low energy events and interactions. Chemists (well, the non-nuclear ones, anyway) talk about it, but physicists do not.25-Jun-2015
Therefore, the common understanding of mass conservation as it is taught in chemistry is not applicable to particle physics. In particle decay, the total mass of particles can change; however, energy, including mass energy, is conserved.
