Search For Rare And Forbidden Eta ' Decays

We have searched for rare and forbidden decays of the eta' meson in hadronic events at the CLEO II detector. The search is conducted on 4.80 fb(-1) of e(+)e(-) collisions at 10.6 GeV center-of-mass energy at the Cornell Electron Storage Ring. We find no signals, and set 90% confidence level upper limits of their branching fractions: B(eta' --> e(+)e(-)eta) < 2.4 x 10(-3), B(eta' --> e(+)e(-) pi(0)) < 1.4 x 10(-3), B(eta' --> e(+)e(-) gamma) < 0.9 x 10(-3), and B(eta' --> e mu) < 4.7 x 10(-4). We also fit the matrix element of the eta' --> pi(+)pi(-) eta Dalitz plot with the parametrization \M\(2) = A\1 + alpha gamma\(2), where gamma is a linear function of the kinetic energy of the eta, and find Re(alpha) =-0.021 +/- 0.025.