Abouzaid E. et al.YEE HSIUNG2021-07-282021-07-28201924700010https://www.scopus.com/inward/record.uri?eid=2-s2.0-85072054469&doi=10.1103%2fPhysRevD.100.032003&partnerID=40&md5=1ad7210e8f6420f80c2430af39306c9ahttps://scholars.lib.ntu.edu.tw/handle/123456789/575205We present a measurement of B(π0→e+e-γ)/B(π0→γγ), the Dalitz branching ratio, using data taken in 1999 by the E832 KTeV experiment at Fermi National Accelerator Laboratory. We use neutral pions from fully reconstructed KL decays in flight; the measurement is based on ?60 thousand KL→π0π0π0→γγγγe+e-γ decays. We normalize to KL→π0π0π0→6γ decays. We find B(π0→e+e-γ)/B(π0→γγ) (me+e->15 MeV/c2)=[3.920±0.016(stat)±0.036(syst)]×10-3. Using the Mikaelian and Smith prediction for the e+e- mass spectrum, we correct the result to the full e+e- mass range. The corrected result is B(π0→e+e-γ)/B(π0→γγ)=[1.1559±0.0047(stat)±0.0106(syst)]%. This result is consistent with previous measurements, and the uncertainty is a factor of 3 smaller than any previous measurement. ? 2019 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the "https://creativecommons.org/licenses/by/4.0/" Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP3[SDGs]SDG17journal article10.1103/PhysRevD.100.0320032-s2.0-85072054469