Solutionįor reaction (a), the net baryon number of the two reactants is 0 + 1 = 1 0 + 1 = 1 and the net baryon number of the four products is 0 + 1 + 0 + 0 = 1. ( a ) π − + p → π 0 + n + π − + π + ( b ) p + p − → p + p + p − ( a ) π − + p → π 0 + n + π − + π + ( b ) p + p − → p + p + p −ĭetermine the total baryon number for the reactants and products, and require that this value does not change in the reaction. No conservation law considered thus far prevents a neutron from decaying via a reaction such as These are by no means the only conservation laws in particle physics. In the next section, we describe three less-familiar conservation laws: baryon number, lepton number, and strangeness. No known physical processes violate charge conservation. Charge lost in one place is gained in another because charge is carried by particles. For example, charge is conserved in all electrostatic phenomena. In previous chapters, we encountered other conservation laws as well. In particular, the relativistic momentum of a particle differs from its classical momentum by a factor γ = 1 / 1 − ( v / c ) 2 γ = 1 / 1 − ( v / c ) 2 that varies from 1 to ∞, ∞, depending on the speed of the particle.
As discussed in Relativity, the special theory of relativity modifies definitions of momentum, energy, and other familiar quantities. The annihilation of an electron and positron at rest, for example, cannot produce just one photon because this violates the conservation of linear momentum. Strong evidence exists that energy, momentum, and angular momentum are all conserved in all particle interactions.
Use baryon number, lepton number, and strangeness conservation to determine if particle reactions or decays occurĬonservation laws are critical to an understanding of particle physics.Use rules to determine the total baryon number, lepton number, and strangeness of particles before and after a reaction.Distinguish three conservation laws: baryon number, lepton number, and strangeness.By the end of this section, you will be able to:
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