# Question Video: Recognizing an Equation to Represent a Muon-Antimuon Annihilation Physics • 9th Grade

Which of the following equations shows a muon and an antimuon annihilating to produce a photon? [A] 𝜇⁻ + 𝜇⁺ ⟶ 𝛾 [B] 𝑑 + 𝑑 bar ⟶ 𝛾 [C] 𝑒⁻ + 𝑒⁺ ⟶ 𝛾 [D] 𝑢 + 𝑢 bar ⟶ 𝛾 [E] 𝑇⁻ + 𝑇⁺⟶ 𝛾

01:29

### Video Transcript

Which of the following equations shows a muon and an antimuon annihilating to produce a photon?

We see these five different answer choices and realize that the solution essentially comes down to understanding what are the symbols that represent a muon, an antimuon, and a photon. If we know what those symbols are, then we’ll be able to identify which of these answer choices is correct.

If we focus on the product of this interaction, a photon, we can recall that the symbol for a photon is the Greek letter 𝛾. But notice that all five answer choices involve that product. So, that doesn’t help us narrow the field down. Our choice comes down then to which symbol represents a muon and an antimuon. We’re helped a bit by the fact that even these names, muon and antimuon, suggest what Greek letter represents these terms.

In the very name muon, we can see the Greek letter 𝜇. And that letter is written this way in lowercase. To complete the symbol for a muon particle, we add a minus sign to the top right of the Greek letter 𝜇. That’s because this particle has a negative electric charge. So, if the symbol for a muon is 𝜇 minus, then the symbol for an antimuon must be 𝜇 plus.

Scanning through our list of options, we see that answer option (A) has these symbols in it. This answer choice then, answer choice (A), is the symbolic representation of a muon and an antimuon annihilating one another to produce a photon.