1. The problem statement, all variables and given/known data There are a lot of similar problems so it is a general question, if you have a nuclear reaction with two particles before, and two afther the process ¿How do you calculate if the Isospin is conserved?¿or the angular momentum?. For example(it could be any other) we have this reaction: Pi- + proton----------->Pi0 + neutron And the question is if it is allowed or forbidden and why. 2. Relevant equations Conservation laws of nuclear quantities. 3. The attempt at a solution Well I started searching wich were the properties of these particles: For the pions I=1, and for the p,n the I=1/2 so now ¿Should i compose the total Isospin using clebsh jordan coefficients?.Or can i consider this?: 1+1/2=1+1/2 so I is conserved. The same for the angular momentum. ¿What do you think?