Observation of psi(3770)->gamma chi(c1)->gamma gamma J/psi

Abstract

From e(+)e(-) collision data acquired with the CLEO detector at the Cornell Electron Storage Ring, we observe the non-D (D) over bar decay psi(3770)->gamma chi(c1) with a statistical significance of 6.6 standard deviations, using the two-photon cascades to J/psi and J/psi ->center dot(+)center dot(-). We determine sigma(e(+)e(-)->psi(3770))xB(psi(3770)->gamma chi(c1))=(18.0 +/- 3.3 +/- 2.5) pb and branching fraction B(psi(3770)->gamma chi(c1))=(2.8 +/- 0.5 +/- 0.4)x10(-3). We set 90% C.L. upper limits for the transition to chi(c2) (chi(c0)): sigma xB < 5.7 pb (< 282 pb) and B < 0.9x10(-3) (< 44x10(-3)). We also determine Gamma(psi(3770)->gamma chi(c1))/Gamma(psi(3770)->pi(+)pi(-)J/psi)=1.5 +/- 0.3 +/- 0.3 (> 1.0 at 90% C.L.), which bears upon the interpretation of X(3872).