Antiprotons can be produced when a proton with sufficient...

Antiprotons can be produced when a proton with sufficient energy hits a stationary proton. Even if there is enough energy, which of the following reactions will not happen? $$ \begin{array}{l} p+p \rightarrow p+\bar{p} \\ p+p \rightarrow p+p+\bar{p} \\ p+p \rightarrow p+p+p+\bar{p} \\ p+p \rightarrow p+e^{+}+e^{+}+\bar{p} \end{array} $$

Antiprotons can be produced when a proton with sufficient energy hits a stationary proton. Even if there is enough energy, which of the following reactions will not happen?
$$
\begin{array}{l}
p+p \rightarrow p+\bar{p} \\
p+p \rightarrow p+p+\bar{p} \\
p+p \rightarrow p+p+p+\bar{p} \\
p+p \rightarrow p+e^{+}+e^{+}+\bar{p}
\end{array}
$$

Key Concepts

Particle–Antiparticle Pair Production

In high-energy particle collisions, sufficient energy can create particle–antiparticle pairs. However, while energy might allow for pair production, all other conservation laws such as baryon number, charge, and lepton number must also be satisfied. This concept explains why producing an antiproton typically requires the simultaneous production of an extra proton or another baryon to balance the baryon number.

Baryon Number Conservation

Baryon number conservation is a fundamental principle in particle physics stating that the total baryon number (the number of baryons minus the number of antibaryons) must remain constant in any reaction. In proton–proton collisions, the initial baryon number is two (since each proton has a baryon number of +1), and any reaction products must add up to the same total. This principle determines whether a proposed reaction is physically allowed regardless of the energy available.

Lepton Number Conservation

Lepton number conservation is the rule that the number of leptons minus the number of antileptons remains constant in a reaction. Although not all reactions involving antiprotons also involve leptons, any inclusion of leptonic particles (or antiparticles) must adhere to this conservation law. Violating lepton number conservation means a reaction cannot occur even if the energy criteria are met.

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