Some general class in data analysis 1, Reaction_CM_Lab: for target experiment, you need transfer the momentum from lab to CM or from CM to lab. Although the TLorentzVector@ROOT, you still need to calculate the beta or gamma of CM. You only need to initial the Target(A,Z), Projectile(A,Z), then this class can handle the following things. You can see the Test_Reaction_CM_Lab.C.