The mass of the J/ is m J = 3.097 GeV and its width is =

The mass of the J/ψ is m_J = 3.097 GeV and its width is Γ = 91 keV. What is its lifetime? If it is produced with p_J = 5 GeV in the L reference frame, what is the distance travelled in a lifetime? Consider the case of a symmetric J/ψ → e⁺e^– decay, i.e. with the electron and the positron at equal and opposite angles ±θ_e to the direction of the J/ψ. Find this angle and the electron energy in the L reference frame. Find θ_e if p_J = 50 GeV.