Observation of the decay D0 ??-?+??

Abstract

By analyzing an e+e- annihilation data sample corresponding to an integrated luminosity of 2.93 fb-1 collected at a center-of-mass energy of 3.773 GeV with the BESIII detector, we measure the branching fraction of the D0??-?+?? decay for the first time. We obtain BD0??-?+??=(1.35±0.09stat±0.09syst)×10-3. Using the world average of BD0??-e+?e, we find a branching fraction ratio of BD0??-?+??/BD0??-e+?e=0.90±0.11, which agrees with the theoretical expectation of lepton flavor universality within the uncertainty. Combining the world average of BD+??0?+?? and the lifetimes of D0(+), we obtain a partial decay width ratio of ?D0??-?+??/(2?D+??0?+??)=0.71±0.14, which is consistent with the isospin symmetry expectation of unity within 2.1?. For the reported values of BD0??-?+??/BD0??-e+?e and ?D0??-?+??/2?D+??0?+??, the uncertainty is the quadratic sum of the statistical and systematic uncertainties. © 2021 authors. Published by the American Physical Society.