Determination of the Total Width of the η' Meson

Taking advantage of both the low-emittance proton beam of the cooler synchrotron COSYand the high momentum precision of the COSY-11 detector system, the mass distribution of the eta' meson was measured with a resolution of 0: 33 MeV/c(2) (FWHM), improving the experimental mass resolution by almost an order of magnitude with respect to previous results. Based on the sample of more than 2300 reconstructed pp -> pp eta' events, the total width of the eta' meson was determined to be Gamma(eta') = 0.226 +/- 0: 017(stat) +/- 0: 014(syst) MeV/c(2).