Measurement of ${\rm Y}(1S+2S+3S)$ production in $p+p$ and Au + Au collisions at $\sqrt{s_{\mathit{NN}}}=200$ GeV

Measurements of bottomonium production in heavy-ion and $p+p$ collisions at the Relativistic Heavy Ion Collider (RHIC) are presented. The inclusive yield of the three ${\rm Y}$ states, ${\rm Y}(1S+2S+3S)$, was measured in the PHENIX experiment via electron-positron decay pairs at midrapidity for $\mathrm{Au}+\mathrm{Au}$ and $p+p$ collisions at $\sqrt{s_{\mathit{NN}}}=200$ GeV. The ${\rm Y}(1S+2S+3S)\to e^{+}{e}^{-}$ differential cross section at midrapidity was found to be $B_{\mathrm{ee}}d\sigma /dy=108\pm 38\left(\text{stat}\right)\pm 15\left(\text{syst}\right)\pm 11\left(\text{luminosity}\right)$ pb in $p+p$ collisions. The nuclear modification factor in the 30% most central $\mathrm{Au}+\mathrm{Au}$ collisions indicates a suppression of the total ${\rm Y}$ state yield relative to the extrapolation from $p+p$ collision data. The suppression is consistent with measurements made by STAR at RHIC and at higher energies by the CMS experiment at the Large Hadron Collider.

Figure 1

Compilation of medium temperatures relative to the critical temperature $\left(T_c\right)$, where quarkonium states are dissociated in the QGP. Note that these estimations were performed assuming different $T_c$ values. Each horizontal bar corresponds to one estimation and its temperature extension (when applied) represents the range where the quarkonia state undergoes a mass/size modification until it completely melts. Techniques used in calculations: lattice QCD [5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15], QCD sum rules [4, 16, 17, 18, 19, 20], AdS/QCD [21, 22, 23, 24], effective field theories [27, 28], and potential models [15, 29, 30, 31, 32, 33, 34, 35]. The shaded band from $1.8T/T_c$ to $3.5T/T_c$ represents the hydrodynamic estimation for the peak temperature reached in $\mathrm{Au}+\mathrm{Au}$ collisions at 200 GeV [36].

Figure 2

The PHENIX Central Arm Spectrometers for the 2010 data-taking period.

Figure 3

Distribution of the parameter used to identify electrons with the EMCal. $E/p$ is the ratio between the energy deposited by the particle in the EMCal cluster and its momentum, ${\sigma }_{E/p}$ is the variance of the expected energy/momentum expected for electrons. The sample shown in (a) from $p+p$ collisions and (c) from $\mathrm{Au}+\mathrm{Au}$ collisions is from unlike-sign electron pairs (containing $\mathrm{signal}+\mathrm{combinatorial}$ background) and like-sign pairs (containing only background). Panels (b) and (d) are the background-subtracted distributions along with the expected line shape from pure electrons.

Figure 4

Invariant mass distribution of simulated ${\rm Y}(1S+2S+3S)$ using the PHENIX detector simulation and relative ${\rm Y}$ yields from CDF experiment [47] in the 2006 run (a) and the 2010 run (b) detector configurations.

Figure 5

Invariant mass distribution of unlike-sign and like-sign dielectrons in the ${\rm Y}$ mass region taken from $p+p$ (a), and $\mathrm{Au}+\mathrm{Au}$ collisions (b).

Figure 6

Fitted components to the correlated dielectron mass spectrum in the $p+p$ sample. The bands correspond to the uncertainties obtained from the fit, changes in the heavy flavor generator, and theoretical uncertainties in the Drell-Yan contribution.

Figure 7

Fits to the correlated dielectron mass distribution around the ${\rm Y}$ region obtained in $p+p$ collisions (a) and $\mathrm{Au}+\mathrm{Au}$ collisions in three centrality bins (b),(c),(d). The bands correspond to fitting and theoretical uncertainties for the Drell-Yan estimation. Fitting results are used only for correlated background estimations.

Figure 8

Transverse momentum dependence of acceptance corrected dielectron net counts in the ${\rm Y}$ mass region from $p+p$ (a) and centrality integrated $\mathrm{Au}+\mathrm{Au}$ (b) collisions. The lines are functions and ${\rm Y}$ yield estimations (color evaporation model (CEM) [62] and pythia [61]) fitted to the distributions.

Figure 9

Dependence of the $\mathrm{acceptance}\times \mathrm{efficiency}$ for detected ${\rm Y}$ dielectron decays in $p+p$ and $\mathrm{Au}+\mathrm{Au}$ collisions on (a) transverse momentum in 0%–92% centrality and (b) collision centrality. The bars represent statistical uncertainties in the simulation.

Figure 10

Rapidity dependence of ${\rm Y}(1S+2S+3S)$ yield measured by PHENIX, forward rapidity result from [53], and STAR midrapidity from [54]. The dashed line is a Gaussian function fitted to the points. The points at zero rapidity are shifted for clarity.

Figure 11

Energy dependence of the ${\rm Y}\left(1S+2S+3S\right)$ differential cross section at midrapidity in $p+p$ and $p+\overline{p}$ collisions [49, 52, 54, 65, 66, 67, 68, 69, 70, 71, 72]. The curve is the estimation using the color evaporation model [62].

Figure 12

The $N_{\mathrm{coll}}$ normalized invariant yield of ${\rm Y}$'s produced during the $2006 p+p$ and the $2010 \mathrm{Au}+\mathrm{Au}$ operations, as a function of $N_{\mathrm{part}}$.

Figure 13

Nuclear modification factor for centrality binned data plotted as a function of $N_{\mathrm{part}}$.

Figure 14

Nuclear modification factor for centrality binned data plotted as a function of $N_{\mathrm{part}}$ compared to STAR [54] and CMS results.

Figure 15

A comparison of PHENIX data to the model from Ref. [74] for the strong binding scenario.

Figure 16

A comparison of PHENIX ${\rm Y}$ data to the model from Ref. [74] for the weak and strong binding scenarios.

Figure 17

Centrality-dependent $R_{AA}$ compared to model predictions from Strickland and Bazow [76].