# How could this,Sigma0 decay into Lambda and gamma, happens?

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1. Nov 9, 2015

### HanningWu

I found an article, titled Electromagnetic Decay of the Σ0(1385) to Λγ , in the arXiv telling that the reaction
Σ0→Λ+γ
can happen through electromagnetic interaction. However, if I examine the conservation of parity. Parity on the left side is even(P(Σ0)=+), but that on the right side is odd(P(Λ)=+, while P(γ)=-). In this sense, the parity conservation is violated. In addition, I am convinced that the parity is conserved under electromagnetic interaction, so this reaction by no means can exist.

2. Nov 9, 2015

### Orodruin

Staff Emeritus
Those are the intrinsic parities of the particle states. You also need to consider the parity of the wave-function of the final state.

3. Nov 9, 2015

### HanningWu

Thank you so much! Problem solved.

4. Nov 9, 2015

### HanningWu

Since I can't simply multiply the parity of the Lambda bayon and the photon, how can I calculate the parity of the final state?

5. Nov 9, 2015

### Staff: Mentor

You can, but you also have to multiply it with the parity of the wave-function combining the two particles.

6. Nov 9, 2015

### HanningWu

Does "the parity of the wave-function combining the two particle" mean the parity valued (-1)L, where L is the orbital quantum number?

7. Nov 10, 2015

Right.