Higher-order multipole amplitude measurement in $psi(2S)togammachi_{c2}$

Using $106times10^6$ $psi(2S)$ events collected with the BESIII detector at the BEPCII storage ring, the higher-order multipole amplitudes in the radiative transition $psi(2S)togammachi_{c2}togammapipi/gamma KK$ are measured. A fit to the $chi_{c2}$ production and decay angular distributions yields $M2=0.046pm0.010pm0.013$ and $E3=0.015pm0.008pm0.018$, 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 $4.4sigma$ statistical significance and is consistent with the charm quark having no anomalous magnetic moment.