We report the first measurement of the semileptonic decay $D_s^+ \to K^0\mu^+\nu_\mu$, using a sample of $e^+e^-$ annihilation data corresponding to an integrated luminosity of $7.33~\mathrm{fb}^{-1}$ collected at center-of-mass energies between $4.128$ and $4.226~\mathrm{GeV}$ with the BESIII detector at the BEPCII collider. The branching fraction of the decay is measured to be $$\mathcal{B}(D_s^+ \to K^0\mu^+\nu_\mu) = (2.89 \pm 0.27\,(\mathrm{stat}) \pm 0.12\,(\mathrm{syst})) \times 10^{-3},$$ where the first uncertainty is statistical and the second is systematic. Based on a simultaneous fit to the partial decay rates in $q^2$ intervals measured in the $D_s^+ \to K^0\mu^+\nu_\mu$ and $D_s^+ \to K^0e^+\nu_e$ decays, the product of the form factor and the Cabibbo-Kobayashi-Maskawa matrix element is measured to be $$f_+^{K^0}(0)\,|V_{cd}| = 0.140 \pm 0.008\,(\mathrm{stat}) \pm 0.003\,(\mathrm{syst}),$$ which is the most precise determination to date. In addition, lepton flavor universality is tested.
First Measurement of the 𝐷+𝑠 →𝐾0𝜇+𝜈𝜇 Decay
Garzia, I.;Melendi, F. M.;
2026
Abstract
We report the first measurement of the semileptonic decay $D_s^+ \to K^0\mu^+\nu_\mu$, using a sample of $e^+e^-$ annihilation data corresponding to an integrated luminosity of $7.33~\mathrm{fb}^{-1}$ collected at center-of-mass energies between $4.128$ and $4.226~\mathrm{GeV}$ with the BESIII detector at the BEPCII collider. The branching fraction of the decay is measured to be $$\mathcal{B}(D_s^+ \to K^0\mu^+\nu_\mu) = (2.89 \pm 0.27\,(\mathrm{stat}) \pm 0.12\,(\mathrm{syst})) \times 10^{-3},$$ where the first uncertainty is statistical and the second is systematic. Based on a simultaneous fit to the partial decay rates in $q^2$ intervals measured in the $D_s^+ \to K^0\mu^+\nu_\mu$ and $D_s^+ \to K^0e^+\nu_e$ decays, the product of the form factor and the Cabibbo-Kobayashi-Maskawa matrix element is measured to be $$f_+^{K^0}(0)\,|V_{cd}| = 0.140 \pm 0.008\,(\mathrm{stat}) \pm 0.003\,(\mathrm{syst}),$$ which is the most precise determination to date. In addition, lepton flavor universality is tested.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
