2026/07/27 by BESIII Collaboration, M. Ablikim, M. N. Achasov +773
#hep-ex
The branching fractions of D0→ π-e+νe, D0→ π-μ+νμ, D+→ π0e+νe, and D+→ π0μ+νμ are measured to be (2.950±0.017\rm stat.± 0.017\rm syst.)×10-3, (2.817±0.037\rm stat.± 0.019\rm syst.)×10-3, (3.622±0.034\rm stat.± 0.018\rm syst.)×10-3, and (3.507±0.043\rm stat.± 0.026\rm syst.)×10-3 using e+e- collision data with an integrated luminosity of 20.3 fb-1 collected at the center-of-mass energy of 3.773 GeV with the BESIII detector. The partial decay rates of these four decays are measured with the best precision to date and their forward-backward asymmetries are determined for the first time. By performing a simultaneous fit to these results, the product of the hadronic transition form factor fD→π+(0) and the modulus of the c→ d Cabibbo-Kobayashi-Maskawa matrix element |Vcd| is given by fD→π+(0)|Vcd|=0.1425±0.0005\rm stat.±0.0003\rm syst.. Taking the |Vcd| provided by the standard model global fit and the fD→π+(0) calculated from the lattice quantum chromodynamics as input, we obtain fD→π+(0)=0.6339±0.0024\rm stat.±0.0014\rm syst. and |Vcd|=0.2262±0.0008\rm stat.±0.0005\rm syst.±0.0018\rm LQCD., respectively. The reported results have the best precision to date. We also search for the scalar current contribution in the c→ d ℓ+νℓ transition and determine Re(CSμ)= 0.022 ± 0.023\rm stat.± 0.003\rm syst. and |\rm Im(CSμ)|=0.000 ± 0.038\rm stat. ± 0.012\rm syst.. In addition, the lepton flavor universality is tested with the ratios of the decay rates between semimuonic and semielectronic decays in full and several ℓ+ν_ℓ four-momentum transfer ranges.