We present the first comprehensive measurement of $D^{ 0}, D^{ +}, D^{ *+}$ and their charge conjugate states at mid-rapidity in $d$+Au collisions at $\sqrt{ s_{ _{ NN}}}$=200 GeV using the STAR TPC. The directly measured open charm multiplicity distribution covers a broad transverse momentum region of 0$<p_{ T}<11$ GeV/$c$. The measured $dN/dy$ at mid-rapidity for $D^{ 0}$ is $0.0265\pm 0.0036 (stat.) \pm 0.0071 (syst.)$ and the measured $D^{ *+}/D^{ 0}$ and $D^{ +}/D^{ 0}$ ratios are approximately equal with a magnitude of $0.40\pm 0.09(stat.) \pm 0.13(syst.)$. The total $c\bar{ c}$ cross section per nucleon-nucleon collision extracted from this study is $1.18 \pm 0.21(stat.) \pm 0.39(syst.) $mb. The direct measurement of open charm production is consistent with STAR single electron data. This cross section is higher than expectations from PYTHIA and other pQCD calculations. The measured $p_{ T}$ distribution is harder than the pQCD prediction using the Peterson fragmentation function.
Categories: nucl-ex