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

Abstract

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 MeV,Mψ′=3686.111 ± 0.025 ± 0.009 MeV. The relative measurement accuracy has reached 4⋅10−6 for J/ψ and 7⋅10−6 for ψ′, approximately 3 times better than in the previous precise experiments. The description of the experiment and the error analysis can be found in hep‐ex/0306050, Phys. Lett. B573 (2003) 63–79.