Why is the eta meson's composition known as the singlet state?

In summary, the composition of eta prime meson is known as the singlet state because it is a spin 0 linear combination of two spin 1/2 particles (quarks) and is an eigenvalue of S^2 with eigenvalue 0. This state is a result of the SU(3) flavor symmetry and is known as the singlet state because it has a total spin of 0.
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Manman
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The article you link to doesn't have the word singlet in it, but if I'm not mistaken it's a singlet under SU(3) flavor symmetry (the one that would be exact if the up, down, and strange quarks all had equal mass).
 
  • #3
Generally, if you have two spin 1/2 particles, they transform as some linear combination of a (total) spin 1 and a (total) spin 0 part. If you look at the state for the eta meson, though... hit it with an S^2. The u, ubar, d, dbar, s and sbar parts are all eigenvalues of S^2 with eigenvalue (1/2)(1/2+1) = 3/4. You can check that S^2|eta> = 0.

Recall from QM that if you have two spin 1/2 particles, there are four states (up up, up down, down up, down down). We can instead use the basis of total spin and the total state's S_z. There are 3 states with total spin 1 and 1 state with total spin 0. These are known as the triplet and singlet states, respectively. The eta, being a spin 0 linear combination of "two" spin 1/2 particles (two quarks), could have either spin 1 or spin 0; this particular state, as argued above, is the spin 0 part. That's why it gets the name "singlet".
 

1. What is an Eta meson?

An Eta meson is a subatomic particle that belongs to the family of mesons, which are made up of a quark and an antiquark. It is denoted by the symbol η and has a mass of about 547.862 MeV/c².

2. What is the singlet state of an Eta meson?

The singlet state of an Eta meson refers to the state in which its spin is zero. This means that the two quarks within the meson have their spins aligned in opposite directions, resulting in a net spin of zero.

3. How is the singlet state of an Eta meson different from its triplet state?

The singlet state of an Eta meson has a spin of zero, while the triplet state has a spin of one. This means that in the triplet state, the two quarks within the meson have their spins aligned in the same direction, resulting in a net spin of one.

4. What is the significance of the singlet state in particle physics?

The singlet state of an Eta meson is significant in particle physics as it helps to explain the strong force that binds quarks together. The spin of a particle affects its interactions with other particles, and the singlet state of the Eta meson has a different interaction compared to its triplet state.

5. How is the singlet state of an Eta meson produced in experiments?

The singlet state of an Eta meson can be produced in experiments by colliding high-energy particles, such as protons, together. This collision creates a high-energy environment where new particles, including the Eta meson, can be formed. Scientists can then detect and study the characteristics of the mesons produced in these collisions, including the singlet state of the Eta meson.

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