Ablikim, M (reprint author), Inst High Energy Phys, Beijing 100049, Peoples R China.
Using 106 x 10(6) psi' events collected with the BESIII detector at the BEPCII storage ring, the higher-order multipole amplitudes in the radiative transition psi' -> gamma chi(c2) -> gamma pi(+)pi(-)/gamma K+K- are measured. A fit to the chi(c2) production and decay angular distributions yields M2 = 0.046 +/- 0.010 +/- 0.013 and E3 = 0.015 +/- 0.008 +/- 0.018, where the first errors are statistical and the second systematic. Here M2 denotes the normalized magnetic quadrupole amplitude and E3 the normalized electric octupole amplitude. This measurement shows evidence for the existence of the M2 signal with 4.4 sigma statistical significance and is consistent with the charm quark having no anomalous magnetic moment.