particle physics - What's the symbol for the antiparticle of the $Delta^+$ baryon?

It can't be $\Delta^-$ since that is another particle also made up of quarks (not antiquarks). I can think of four possibilities:

1. $\overline\Delta^+$


2. $\overline{\Delta^+}$


3. $\overline\Delta^-$


4. $\overline{\Delta^-}$

I am sure someone has asked a similar question, but I failed at searching for it.

Answer

The $\Delta$ is a quartet of particles with isospin 3/2: $$ \Delta^-, \Delta^0, \Delta^+, \Delta^{++} $$ I would expect the anti-$\Delta$ to be written $\bar\Delta$, with the four isospin projections $$ \bar\Delta^{--}, \bar\Delta^-, \bar\Delta^0, \bar\Delta^+ $$ In this case the antiparticle of the $\Delta^+$ would be the $\bar\Delta^-$.

If you'd like a canonical reference, look for a paper about pion production with antiproton beams. Note that there's a whole spectrum of $\Delta$ resonances, not just the lightest one at 1232 MeV.