Observation of the semileptonic decays D0→KS0π−π0e+νe and D+→KS0π+π−e+νe

Abstract

By analyzing e+e− annihilation data 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, the first observation of the semileptonic decays D0→KS0π−π0e+νe and D+→KS0π+π−e+νe is reported. In the hypothesis that all events correspond to K1(1270) decays, the branching fractions are measured to be BD0→K11270−→KS0π−π0e+νe=1.69−0.46+0.53±0.15×10−4 and BD+→K¯112700→KS0π+π−e+νe=1.47−0.40+0.45±0.14×10−4 with statistical significance of 5.4σ and 5.6σ, respectively. When combined with measurements of the K1(1270) → K+π−π decays, the absolute branching fractions are determined to be BD0→K11270−e+νe=1.08−0.13−0.10+0.14+0.08±0.21×10−3 and BD+→K¯112700e+νe=1.70−0.23+0.26±0.13±0.35×10−3. The first and second uncertainties are statistical and systematic, respectively, and the third uncertainties originate from the assumed branching fractions of the K1(1270) → Kππ decays.