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My understanding is that vectors and pseudooscalars change sign under parity operation and pseudovectors and scalars do not.

However, I don't understand what the difference between a vector and scalar are when applied to elementary particles. When looking at real space, the difference is obvious (vectors have different elements while scalars only have one), but it is unclear in the case of particles. How can there be mesons that are vectors and other mesons that are scalars. Wikipedia tells me that vector mesons have total spin 1 while scalar mesons have spin 0. Are the terms vector and scalar used to simply differentiate between mesons that have spin 0 and spin 1?

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The terms "scalar" and "vector" refer to the representation of the Lorentz group the quantum field associated to the particle transforms in. Indeed, a "scalar" field has particles with spin-0 associated to it, while a "vector" field has particles with spin-1 associated to it, but the terminology really comes from how the quantum field looks. On the level of the particles, all you see of that is their spin, however.

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  • $\begingroup$ Thanks for the answer. The book I'm reading, (Introduction to Elementary Particles, Griffiths), introduces the terminology "scalar" and "vector" before talking about quantum fields so I was confused, but now it makes sense. $\endgroup$ – honey.mustard Dec 11 '15 at 20:07

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