Parity of a decay

Question

If a particle of unknown intrinsic parity decays into 2 particles each with negative intrinsic parity, does that necessarily imply that the original particle also has negative parity?

Answer 1

No, actually it implies that the original particle has positive parity. That's because parity is a multiplicative quantum number, which means that when you want to find the overall parity of a system that consists of multiple parts, you multiply the parities of the individual parts. If you have two decay products each with parity -1, then you multiply them together and get an overall parity of +1.

Of course this all assumes that you're talking about a decay where parity is conserved. Otherwise, the parity of the products doesn't necessarily imply anything in a single case.