1. The problem statement, all variables and given/known data Meson B+ decays at J/ψ and K+. we know the masses of the particles and we are looking for the angle between the products when B+ has a momentum of 5GeV in lab frame. 2. Relevant equations 3. The attempt at a solution i found the momentum and energies at cm frame (easy..) then i assumed that B+ is mooving at x axes (in lab) i analized momentums of products (both in cm and lab) in x axes to use the Lorentz transformations qx=q*cosθ qy=q*sinθ Lorentz: qxL=γ(q*cosθ+uE*) qyL=q*sinθ so tanΘL=qyL/qxL how can i find the angle θ ??? do i miss something? i think i don't have enough data.