Observation of the semimuonic decay <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mi>D</mml:mi><mml:mo>+</mml:mo></mml:msup><mml:mo stretchy="false">→</mml:mo><mml:mi>ω</mml:mi><mml:msup><mml:mi>μ</mml:mi><mml:mo>+</mml:mo></mml:msup><mml:msub><mml:mi>ν</mml:mi><mml:mi>μ</mml:mi></mml:msub></mml:math>
M. Ablikim, М. Н. Ачасов, P. Adlarson, S. Ahmed, M. Albrecht, A. Amoroso, Q. An, Anita, Y. Bai, O. Bakina, R. Baldini Ferroli, I. Balossino, Y. Ban, K. Begzsuren, J. V. Bennett, N. Berger, M. Bertani, D. Bettoni, F. Bianchi, J. Biernat, J. Bloms, A. Bortone, I. Boyko, R. A. Briere, H. Cai, X. Cai, A. Calcaterra, G. F. Cao, N. Cao, S. A. Çetin, J. F. Chang, W. L. Chang, G. Chelkov, D. Y. Chen, G. Chen, H. S. Chen, M. L. Chen, S. J. Chen, X. R. Chen, Y. B. Chen, W. Cheng, G. Cibinetto, F. Cossio, X. F. Cui, H. L. Dai, J. P. Dai, X. Dai, A. Dbeyssi, R. B. de Boer, D. Dedovich, Z. Y. Deng, A. Denig, I. Denysenko, M. Destefanis, F. De Mori, Y. Ding, C. Dong, Jinxiang Dong, L. Y. Dong, M. Y. Dong, S. X. Du, J. Fang, S. S. Fang, Y. Fang, R. Farinelli, L. Fava, F. Feldbauer, G. Felici, C. Q. Feng, M. Fritsch, C. D. Fu, Y. Fu, X. L. Gao, Y. Gao, Y. Gao, Yanyan Gao, I. Garzia, E. M. Gersabeck, A. Gilman, K. Goetzen, L. Gong, W. X. Gong, W. Gradl, M. Greco, L. M. Gu, M. H. Gu, S. Gu, Y. T. Gu, C. Y. Guan, A. Q. Guo, L. Guo, R. P. Guo, Y. P. Guo, Y. P. Guo, A. Guskov, S. Han, T. T. Han, T. Z. Han, X. Q. Hao, F. A. Harris
Abstract
We report the first observation of the semimuonic decay ${D}^{+}\ensuremath{\rightarrow}\ensuremath{\omega}{\ensuremath{\mu}}^{+}{\ensuremath{\nu}}_{\ensuremath{\mu}}$ using an ${e}^{+}{e}^{\ensuremath{-}}$ collision data sample corresponding to an integrated luminosity of $2.93\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ collected with the BESIII detector at a center-of-mass energy of 3.773 GeV. The absolute branching fraction of the ${D}^{+}\ensuremath{\rightarrow}\ensuremath{\omega}{\ensuremath{\mu}}^{+}{\ensuremath{\nu}}_{\ensuremath{\mu}}$ decay is measured to be ${\mathcal{B}}_{{D}^{+}\ensuremath{\rightarrow}\ensuremath{\omega}{\ensuremath{\mu}}^{+}{\ensuremath{\nu}}_{\ensuremath{\mu}}}=(17.7\ifmmode\pm\else\textpm\fi{}1.{8}_{\mathrm{stat}}\ifmmode\pm\else\textpm\fi{}1.{1}_{\mathrm{syst}})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$. Its ratio with the world average value of the branching fraction of the ${D}^{+}\ensuremath{\rightarrow}\ensuremath{\omega}{e}^{+}{\ensuremath{\nu}}_{e}$ decay probes lepton flavor universality and it is determined to be ${\mathcal{B}}_{{D}^{+}\ensuremath{\rightarrow}\ensuremath{\omega}{\ensuremath{\mu}}^{+}{\ensuremath{\nu}}_{\ensuremath{\mu}}}/{\mathcal{B}}_{{D}^{+}\ensuremath{\rightarrow}\ensuremath{\omega}{e}^{+}{\ensuremath{\nu}}_{e}}^{\mathrm{PDG}}=1.05\ifmmode\pm\else\textpm\fi{}0.14$, in agreement with the standard model expectation within one standard deviation.