Charm- and bottom-quark production in Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV

The invariant yield of electrons from open-heavy-flavor decays for $1<p_T<8$ GeV/$c$ at midrapidity $\left|y\right|<0.35$ in $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{{}_{NN}}}$ = 200 GeV has been measured by the PHENIX experiment at the BNL Relativistic Heavy Ion Collider. A displaced-vertex analysis with the PHENIX silicon-vertex detector enables extraction of the fraction of charm and bottom hadron decays and unfolding of the invariant yield of parent charm and bottom hadrons. The nuclear-modification factors $R_{AA}$ for electrons from charm and bottom hadron decays and heavy-flavor hadrons show both a centrality and a quark-mass dependence, indicating suppression in the quark-gluon plasma produced in these collisions that is medium sized and quark-mass dependent.

Figure 1

Definition of the distance of the closest approach ${\mathrm{DCA}}_{\mathrm{T}}$ in the transverse plane (normal to the beam direction).

Figure 2

A fit result of the dep distribution for electron candidates with $p_T=6$–7 GeV/$c$ in MB $\mathrm{Au}+\mathrm{Au}$ collisions. The red and green distributions are the estimated contributions for electrons and hadron backgrounds.

Figure 3

The fraction of nonphotonic electrons ($F_{\mathrm{NP}}$) as a function of $p_T$ for MB and the indicated four centrality classes.

Figure 4

The fractions of signal component in isolated electron-track candidates as a function of $p_T$ in MB Au+Au collisions. The isolation cut is applied. The modeling of these backgrounds is described in the text and in Ref. [12].

Figure 5

The invariant yields of $c+b\to e$ as a function of $p_T$ for different Au+Au centrality classes. These spectra are scaled by factors of 10 for clarity.

Figure 6

${\mathrm{DCA}}_{\mathrm{T}}$ distribution of electron candidates for 1.6 $<p_T<$ 1.8 GeV/$c$ in MB collisions. All background components are also plotted.

Figure 7

The measured invariant yield for (black markers) $c+b\to e$ as a function of $p_T$ and refolded yields for (red line) $c+b\to e$, (green line) $c\to e$, and (blue line) $b\to e$ in MB Au+Au collisions.

Figure 8

The measured ${\mathrm{DCA}}_{\mathrm{T}}$ distribution of (black line) electron tracks, (red line) refolded $c+b\to e$, (yellow line) background, (green line)$c\to e$, and (blue line) $b\to e$ in MB Au+Au collisions for $1.6<p_T<1.8$ GeV/$c$.

Figure 9

The fractions of each systematic uncertainty in the invariant yield of (a) $b\to e$ and (b) $c\to e$ (in MB Au+Au collisions.

Figure 10

Comparison of refolded $p_T$ spectrum of (a) $c\to e$ and (b) $b\to e$ in Au+Au collisions to that scaled by $T_{AA}$ in $p+p$ collisions [18].

Figure 11

Comparison of unfolded $p_T$ spectrum of (a) charm hadrons and (b) bottom hadrons in Au+Au collisions to that scaled by $T_{AA}$ in $p+p$ collisions [18].

Figure 12

Unfolded yield of $D^0$ mesons as a function of $p_T$ at midrapidity $\left|y\right|<$ 1, compared to the measurement from STAR [36].

Figure 13

The nuclear modification of $c\to e$ and $b\to e$ as a function of $p_T$ for different centrality classes. The yellow box at unity is the uncertainty on the total normalization.

Figure 14

The nuclear-modification factors of $c\to e$ and $b\to e$ as a function of $p_T$ in MB $\mathrm{Au}+\mathrm{Au}$ Collisions from this work compared with the corresponding measurement from the STAR Collaboration [9].

Figure 15

$R_{AA}$ ratio of $b\to e$ to $c\to e$ as a function of $p_T$ for different centrality classes.

Figure 16

The nuclear modification of charm and bottom hadrons as a function of $p_T$ for different centrality classes. The yellow box at unity is the uncertainty on the total normalization.

Figure 17

The $R_{AA}$ for $c\to e$ and $b\to e$ as a function of $N_{\mathrm{part}}$ in three different $p_T$ ranges. Data points for $c\to e$ and $b\to e$ are shifted by $-2$ and $+2$ from their respective $N_{\mathrm{part}}$ for clarity.

Figure 18

Measured $R_{AA}^{c\to e}$ and $R_{AA}^{b\to e}$ compared to theoretical-model calculations.