Measurements of $D^{0}$ and $D^{*}$ Production in $p$ + $p$ Collisions at $\sqrt{s}$ = 200 GeV

TL;DR

This study measures D0 and D* production cross sections in p+p collisions at √s = 200 GeV with the STAR detector, reconstructing hadronic decays at mid-rapidity and correcting for detector acceptance, efficiency, and trigger/vertex biases. The resulting charm-pair cross section at y=0 is dσ/dy^{cĉ} = 170 ± 45 (stat)^{+38}_{-59} μb, and the total cc̄ cross section is σ_{cc̄} ≈ 797 μb, with results consistent with the upper bound of FONLL pQCD predictions. The pT-differential cross sections favor a PYTHIA tune with reduced primordial kT and weaker parton showering, while aligning with FONLL limits, thereby constraining heavy-flavor production models at RHIC energies. This work provides a crucial baseline for interpreting charm production in heavy-ion collisions and informs theoretical descriptions of charm production in hadronic collisions.

Abstract

We report measurements of charmed-hadron ($D^{0}$, $D^{*}$) production cross sections at mid-rapidity in $p$ + $p$ collisions at a center-of-mass energy of 200 GeV by the STAR experiment. Charmed hadrons were reconstructed via the hadronic decays $D^{0}\rightarrow K^{-}π^{+}$, $D^{*+}\rightarrow D^{0}π^{+}\rightarrow K^{-}π^{+}π^{+}$ and their charge conjugates, covering the $p_T$ range of 0.6$-$2.0 GeV/$c$ and 2.0$-$6.0 GeV/$c$ for $D^{0}$ and $D^{*+}$, respectively. From this analysis, the charm-pair production cross section at mid-rapidity is $dσ/dy|_{y=0}^{c\bar{c}}$ = 170 $\pm$ 45 (stat.) $^{+38}_{-59}$ (sys.) $μ$b. The extracted charm-pair cross section is compared to perturbative QCD calculations. The transverse momentum differential cross section is found to be consistent with the upper bound of a Fixed-Order Next-to-Leading Logarithm calculation.

Figures (16)

• Figure 1: (color online) Upper Panel: Correlation of $V^{TPC}_{z}$ versus $V^{VPD}_{z}$. Bottom Panel: $\Delta V_z$ distributions. A "good" vertex requirement rejects most of the pileup events. Blue vertical lines indicate the cuts for the $V_z$ selection.
• Figure 2: (color online) Distributions of n$\sigma_{\pi}^{dE/dx}$, n$\sigma_{K}^{dE/dx}$, and n$\sigma_{K}^{TOF}$ versus momentum are shown in panels (a), (b), and (c), respectively. The latter is shown after $dE/dx$ cuts were applied.
• Figure 3: (color online) (a) Invariant mass distributions of raw $K\pi$ combinations for unlike-sign pairs (circles), like-sign pairs (triangles), and kaon momentum rotated pairs (line). (b) Residual distributions after subtracting the like-sign distribution (triangles) and rotation pair distribution (dots) from the unlike-sign distribution.
• Figure 4: (color online) Invariant $K\pi$ mass distributions in the $D^{0}$ mass region after like-sign (a) and track-rotation (b) background subtraction. Solid circles show the signal and a residual background. A Gaussian function and a 2nd order polynomial function were used to describe the signal and residual background, respectively. Open circles show the signal after residual background subtraction.
• Figure 5: (color online) Raw $D^{0}$ signals in different $p_T$ bins after like-sign (a)(c) and track-rotation (b)(d) subtraction.