D* and D Meson Production in Muon Nucleon Interactions at 160 GeV/c

The production of D* and D mesons in inelastic scattering of 160 GeV/c muons off a $^6$LiD target has been investigated with the COMPASS spectrometer at CERN for 0.003 (GeV/c)$^2 < Q^2 < 10$ (GeV/c)$^2$ and 3x10$^-5< x_{Bj}$ < 0.1. The study is based on 8100 events where a $D^0$ or anti $D^0$ is detected subsequently to a $D^{*+}$ or $D^{*-}$ decay, and on 34000 events, where only a $D^0$ or anti $D^0$ is detected. Kinematic distributions of D*, D and $K^*_2$ are given as a function of their energy E, transverse momentum $p_T$, energy fraction z, and of the virtual photon variables nu, $Q^2$ and $x_{Bj}$. Semi-inclusive differential D* production cross-sections are compared with theoretical predictions for D* production via photon-gluon fusion into open charm. The total observed production cross-section for $D^{*\pm}$ mesons with laboratory energies between 22 and 86 GeV is 1.9 nb. Significant cross-section asymmetries are observed between $D^{*+}$ and $D^{*-}$ production for $\nu$ < 40 GeV and z > 0.6.