Search for Radiative Decays of Upsilon(1S) into eta and eta'

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We report on a search for the radiative decay of Upsilon(1S) to the pseudoscalar mesons eta and etaprime in 21.2 +/- 0.2 times 10^6 Upsilon(1S) decays collected with the CLEO III detector at the Cornell Electron Storage Ring (CESR).

• The eta meson was reconstructed in the three modes eta to gamma-gamma, eta to pi+pi-pi0 and eta to 3pi0.
• The etaprime meson was reconstructed in the mode etaprime to pi+ pi- eta with eta decaying through any of the above three modes, and also etaprime to gamma rho, where rho decays to pi^+ pi^-.
• Five out of the seven sub-modes are found to be virtually background-free.