New precision measurement of the J/ψ- and ψ'-meson masses

A new high precision measurement of the J/ψ- and ψ'-meson masses has been performed at the VEPP-4M collider using the KEDR detector. The resonant depolarization method has been employed for the absolute calibration of the beam energy. The following mass values have been obtained: MJ/ψ=3096.917+/-0.010+/-0.007-bar MeV,Mψ'=3686.111+/-0.025+/-0.009-bar MeV. The relative measurement accuracy has reached 4x10-6 for J/ψ and 7x10-6 for ψ', approximately 3 times better than in the previous precise experiments