Measurement of the branching fraction of ψ(2<i>S</i>) → γπ<SUP>0</SUP>

Based on (2712.4 +/- 14.1) x 10(6) psi(2S) events, 7.9 fb(-1) psi(3773) data, and 0.8 fb(-1) off-resonance data samples collected with the BESIII detector, we measure the branching fraction of psi(2S) -> gamma pi(0) and e(+)e(-) -> gamma pi(0) form factor at momentum transfers Q(2) similar to 13 GeV2. The e(+)e(-) -> gamma pi(0) cross section is fitted with considering the interference between the psi(2S) and continuum amplitudes and two solutions are found, B = 3.74 x 10(-7) with phi = 3.93 rad and B = 7.87 x 10(-7) with phi = 2.08 rad. Here, B is the branching fraction of psi(2S) -> gamma pi(0) and phi is the relative phase angle between the psi(2S) and continuum amplitudes. Due to insufficient off-resonance data, the branching fraction B(psi(2S)-> gamma pi(0)) is determined to be in the range [2.7, 9.7] x 10(-7) within 1 standard deviation of the contour region.