Reaction π-p → eta'n in the 15-40 GeV/c momentum range

Measurements were made of the cross section of the reactions π-p → eta'(958)n, eta' → 2γ at momenta of 15, 20, 25, 30, and 40 GeV/c. The experiment was carried out on the IHEP 70 GeV accelerator using the 648 channel hodoscope spectrometer NICE for γ-ray detection. A total of 6000 eta' mesons were recorded. A sharp drop is seen in the differential cross section for t → 0. The dependences of the differential cross sections π-p → eta'n and π-p → etan on t are identical. On the basis of the ratio of the cross sections for these reactions at t = 0, i.e. R(eta'/n)sub(t=0) = 0.55 +- 0.06, the singlet-octet mixing angle for pseudoscalar mesons was determined to be β = -(18.2 +- 1.4)0. (Auth.)