On the mass and width of the Z-boson and other relativistic quasistable particles

摘要: Abstract The ambiguity in the definition for mass and width of relativistic resonances is discussed, particular case Z -boson. This can be removed by requiring that a resonance's Γ (defined Breit–Wigner lineshape) lifetime τ exponential law) always exactly fulfill relation Γ=ℏ/τ . To justify this, one needs Gamow vectors which turn define M R as real part square root Re s S -matrix pole position For -boson this means ≈M −26 MeV ≈Γ −1.2 where are values reported particle data tables.