Well its not really a homework question but I have looked through the tutorials and am still at a loss. 1. The problem statement, all variables and given/known data During weak interactions the particle exchanged is either W- W+ or Z0. The thing is, I get confused which weak interactions involve W- and which involve W+. I know beta minus decay is W- and beta plus W+ but how do I work it out for an unknown reaction? 2. Relevant equations Is charge conservation involved, if so how? Any guidance would be much appreciated.