Jet-Hadron Correlations in $\sqrt{s_{\mathrm{NN}}}=200\mathrm{GeV}$ $p+p$ and Central $\mathrm{Au}+\mathrm{Au}$ Collisions

Azimuthal angular correlations of charged hadrons with respect to the axis of a reconstructed (trigger) jet in $\mathrm{Au}+\mathrm{Au}$ and $p+p$ collisions at $\sqrt{s_{\mathrm{NN}}}=200\mathrm{GeV}$ in STAR are presented. The trigger jet population in $\mathrm{Au}+\mathrm{Au}$ collisions is biased toward jets that have not interacted with the medium, allowing easier matching of jet energies between $\mathrm{Au}+\mathrm{Au}$ and $p+p$ collisions while enhancing medium effects on the recoil jet. The associated hadron yield of the recoil jet is significantly suppressed at high transverse momentum ($p_T^{\text{assoc}}$) and enhanced at low $p_T^{\text{assoc}}$ in 0%–20% central $\mathrm{Au}+\mathrm{Au}$ collisions compared to $p+p$ collisions, which is indicative of medium-induced parton energy loss in ultrarelativistic heavy-ion collisions.

Figure 1

(a) Detector-level $p_T^{\mathrm{jet},\mathrm{rec}}$ spectra of HT trigger jets in $p+p$ and $\mathrm{Au}+\mathrm{Au}$ and of $p+p$ HT trigger jets embedded in $\mathrm{Au}+\mathrm{Au}$ MB events. (b) Ratio of $(1/N)dN/d{p}_T^{\mathrm{jet},\mathrm{rec},\mathrm{Au}+\mathrm{Au}}$ to $(1/N)dN/d{p}_T^{\mathrm{jet},\mathrm{rec},p+p\mathrm{emb}}$ with uncertainties due to the relative tracking efficiency, relative tower energy, and $\mathrm{\Delta }E=+1\mathrm{GeV}/c$ shift. The ratio of $(1/N)dN/d{p}_T^{\mathrm{jet},\mathrm{rec},\mathrm{Au}+\mathrm{Au}}$ to $(1/N)dN/d{p}_T^{\mathrm{jet},\mathrm{rec},p+p}$ is also shown.

Figure 2

Jet-hadron correlations after background subtraction for $10<p_T^{\mathrm{jet},\mathrm{rec}}<15\mathrm{GeV}/c$ and for two ranges in $p_T^{\text{assoc}}$: (a) $0.5<p_T^{\text{assoc}}<1\mathrm{GeV}/c$ and (b) $4<p_T^{\text{assoc}}<6\mathrm{GeV}/c$. The data points from $\mathrm{Au}+\mathrm{Au}$ and $p+p$ collisions are shown with Gaussian fits to the jet peaks and systematic uncertainty bands due to tracking efficiency, the shape of the combinatoric background, and the trigger jet energy scale.

Figure 3

The (a) Gaussian widths of the awayside jet peaks (${\sigma }_{\mathrm{AS}}$) in $\mathrm{Au}+\mathrm{Au}$ (solid symbols) and $p+p$ (open symbols) and (b) awayside momentum difference $D_{\mathit{AA}}$ are shown for two ranges of $p_T^{\mathrm{jet},\mathrm{rec}}$: $10–15\mathrm{GeV}/c$ (red circles) and $20–40\mathrm{GeV}/c$ (black squares). Results for $15–20\mathrm{GeV}/c$ (not shown) are similar. The boundaries of the $p_T^{\text{assoc}}$ bins are shown along the upper axes. YaJEM-DE model calculations (solid and dashed lines) are from Ref. [42].