Observation of the decay D0→ρ−μ+νμ

By analyzing an e+e− annihilation data sample corresponding to integrated luminosity of 2.93 fb−1 collected at a center-of-mass energy 3.773 GeV with the BESIII detector, we measure branching fraction D0→ρ−μ+νμ decay for first time. We obtain BD0→ρ−μ+νμ=(1.35±0.09stat±0.09syst)×10−3. Using world average BD0→ρ−e+νe, find ratio BD0→ρ−μ+νμ/BD0→ρ−e+νe=0.90±0.11, which agrees theoretical expectation lepton flavor universality within uncertainty. Combining BD+→ρ0μ+νμ and lifetimes D0(+), partial width ΓD0→ρ−μ+νμ/(2ΓD+→ρ0μ+νμ)=0.71±0.14, is consistent isospin symmetry unity 2.1σ. For reported values BD0→ρ−μ+νμ/BD0→ρ−e+νe ΓD0→ρ−μ+νμ/2ΓD+→ρ0μ+νμ, uncertainty quadratic sum statistical systematic uncertainties.Received 3 June 2021Accepted 26 October 2021DOI:https://doi.org/10.1103/PhysRevD.104.L091103Published by American Physical Society under terms Creative Commons Attribution 4.0 International license. Further distribution this work must maintain attribution author(s) published article’s title, journal citation, DOI. Funded SCOAP3.Published SocietyPhysics Subject Headings (PhySH)Research AreasBranching fractionLeptonic, semileptonic & radiative decaysParticle interactionsQuark mixingPhysical SystemsCharmed mesonsPropertiesFlavor symmetriesForm factorsTechniquesLepton collidersParticles Fields