Observation of the semimuonic decay D+ -> omega mu(+)upsilon(mu)

We report the first observation of the semimuonic decay D+ -> omega mu(+)upsilon(mu) using an e(+)e(-) collision data sample corresponding to an integrated luminosity of 2.93 fb(-1) collected with the BESIII detector at a center-of-mass energy of 3.773 GeV. The absolute branching fraction of the D+ -> omega mu(+)upsilon(mu) decay is measured to be BD+ -> omega mu(+)upsilon mu = (17.7 +/- 1.8(stat) +/- 1.1(syst)) x 10(-4). Its ratio with the world average value of the branching fraction of the D+ -> omega e(+)upsilon(mu) decay probes lepton flavor universality and it is determined to be BD+ -> omega mu(+)upsilon mu/BD+ -> omega mu(+)upsilon e(PDG) = 1.05 +/- 0.14, in agreement with the standard model expectation within one standard deviation.