# How do you measure the parity of a particle?

When one looks up elementary particles on Wikipedia, as one of their properties their parity is stated. For example the Proton has parity $$+1$$, while a Pion has parity $$-1$$. I understand that you have to define the parity of some particles to have a reference to measure the parity of all particles (since one could just redefine $$+1\mapsto -1$$).

How is the parity of a particle measured in experiment?

• Some elementary introductions such as the one by Perkins devote entire chapters on the elaborate nets of experimental inferences, involving interactions and decays to particles with known parities, leading up to such determinations. You want a vague platitude summary? – Cosmas Zachos May 19 at 16:19
• @CosmasZachos Some general ideas would be nice, since this is not easily found on the internet (see e.g. the Wikipedia article for parity). In my opinion thus this question fits this site quite nicely. – Jannik Pitt May 19 at 16:22
• So you want a listing of examples like this WP one? – Cosmas Zachos May 19 at 16:31
• I strongly recommend against using Wikipedia in any circumstance where you want specific equations. The problem is that things like parity are associated with many arbitrary conventions. Good books pick one convention and stick with it. Wikipedia is cobbled together from many different books, so its conventions are not even consistent with itself. Sometimes you'll even see two adjacent equations with incompatible conventions. – knzhou May 19 at 19:41
• The same problem goes for trying to learn a convention-heavy subject from StackExchange posts -- everybody is using different conventions. The last time I wrote an answer that was explicit about all possible conventions, it turned out to be thousands of words long. Just stick with one good source! – knzhou May 19 at 19:42