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Using $106\times10^6$ $\psi(2S)$ events collected with the BESIII detector atthe BEPCII storage ring, the higher-order multipole amplitudes in the radiativetransition $\psi(2S)\to\gamma\chi_{c2}\to\gamma\pi\pi/\gamma KK$ are measured.A fit to the $\chi_{c2}$ production and decay angular distributions yields$M2=0.046\pm0.010\pm0.013$ and $E3=0.015\pm0.008\pm0.018$, where the firsterrors are statistical and the second systematic. Here $M2$ denotes thenormalized magnetic quadrupole amplitude and $E3$ the normalized electricoctupole amplitude. This measurement shows evidence for the existence of the$M2$ signal with $4.4\sigma$ statistical significance and is consistent withthe charm quark having no anomalous magnetic moment.

Higher-order multipole amplitude measurement in $\psi(2S)\to\gamma\chi_{c2}$