Hi folks -- I am a non-physicist writing a popular piece on particle physics and I have a couple of questions which I suspect will be very easy for you. Any answers would be massively appreciated! (1) Am I right in thinking that the brunt of what particle physicists predict is the probability of getting certain particles out when we smash particles together? Can anyone give me some examples of what PPists predict beyond such probabilities? (2) Am I right in thinking that the probability of getting certain particles out when we smash particles together can be deduced just from a knowledge of the symmetry of the interaction that kicks in when they're smashed together (through the Clebsch-Gordan coefficients)? If so, and relating I guess to the first question, what considerations apart from symmetry do we need in order to deduce the empirical predictions that PPists standardly make? I appreciate there is no exhaustive answer to be given to these questions but thoughts from the initiated would be very gratefully received. Thanks a lot!