Measurement of \psi(3770) parameters

We report the final results of a study of the \psi(3770) meson using a data sample collected with the KEDR detector at the VEPP-4M electron-positron collider. The data analysis takes into account the interference between the resonant and nonresonant $D\bar{D}$ production, where the latter is related to the nonresonant part of the energy-dependent form factor $F_D$. The vector dominance approach and several empirical parameterizations have been tried for the nonresonant $F_D^{\text{NR}}(s)$. Our results for the mass and total width of \psi(3770) are M = 3779.2 ^{+1.8}{-1.7} ^{+0.5}{-0.7} ^{+0.3}{-0.3} MeV, \Gamma =24.9 ^{+4.6}{-4.0} ^{+0.5}{-0.6} ^{+0.2}{-0.9} 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) \Gamma_{ee} = 154 ^{+79}{-58} ^{+17}{-9} ^{+13}{-25} eV, (2) \Gamma{ee} = 414 ^{+72}{-80} ^{+24}{-26} ^{+90}_{-10} eV. Our statistics are insufficient to prefer one solution to another. The solution (2) mitigates the problem of non-$D\bar{D}$ 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 can not be directly compared with the corresponding PDG values obtained ignoring this effect.