Measurement of [formula omitted] parameters

Abstract

We report the final results of a study of the ψ(3770) meson using a data sample collected with the KEDR detector at the VEPP-4M electron–positron collider. The data analysis takes into account interference between the resonant and nonresonant DD¯ production, where the latter is related to the nonresonant part of the energy-dependent form factor FD. The vector dominance approach and several empirical parameterizations have been tried for the nonresonant FDNR(s).Our results for the mass and total width of ψ(3770) areM=3779.2−1.7+1.8−0.7+0.5−0.3+0.3 MeV,Γ=24.9−4.0+4.6−0.6+0.5−0.9+0.2 MeV, where the first, second and third uncertainties are statistical, systematic and model, respectively. For the electron partial width two possible solutions have been found:(1)Γee=154−58+79−9+17−25+13 eV,(2)Γee=414−80+72−26+24−10+90 eV. Our statistics are insufficient to prefer one solution to another. The Solution (2) mitigates the problem of non-DD¯ decays but is disfavored by potential models.It is shown that taking into account the resonance–continuum interference in the near-threshold region affects resonance parameters, thus the results presented cannot be directly compared with the corresponding PDG values obtained ignoring this effect.