Testing of the coalescence mechanism in high energy heavy ion collisions using two-particle correlations with identified particle trigger

In central Au-Au collisions at top RHIC energy, two-particle correlation measurements with identified hadron trigger have shown attenuation of near-side proton triggered jetlike yield at intermediate transverse momentum $\left(p{}_T\right),2<p{}_T<6\mathrm{GeV}/\mathit{c}$. The attenuation was attributed to the anomalous baryon enhancement observed in the single inclusive measurements at the same $p{}_T$ range. The enhancement was found to be in agreement with the models invoking coalescence of quarks as a mechanism of hadronization. Baryon enhancement was also observed at LHC in the single inclusive spectra. We study the consequence of such an enhancement on two-particle correlations at LHC energy within the framework of a multiphase transport (AMPT) model that implements quark coalescence as a mode of hadronization. In this paper we have calculated the proton over pion ratio and the near side per trigger yield associated with pion and proton triggers at intermediate $p{}_T$ from the string melting (SM) version of AMPT. Results obtained are contrasted with the AMPT default (Def.) which does not include coalescence. Baryon enhancement was observed in AMPT SM at intermediate $p{}_T$. Near-side jetlike correlated yield associated with baryon (proton) trigger in the momentum region where baryon generation is enhanced is found to be suppressed as compared to the corresponding yields for the meson (pion) trigger in most central Pb-Pb events. No such effect was found in the default version of AMPT.

Figure 1

(a) The 2D correlation function taking unidentified charged hadrons as both trigger and associated particles. Transverse momentum of trigger and associated particles are mentioned in the text. (b) $\mathrm{\Delta }\varphi$ projection of the 2D function for different $\mathrm{\Delta }\eta$ regions as indicated in the plot. (c) Near-side jetlike region after bulk subtraction.

Figure 2

The ratio of the yields of proton to pion from two versions of AMPT in Pb-Pb collisions at $\sqrt{s}=2.76$ TeV. The ratio in the SM version (a) shows a clear peak around $2 \mathrm{GeV}/\mathit{c}$ as opposed to the default version (b) which does not show any such peak.

Figure 3

$\mathrm{\Delta }\eta \text{−}\mathrm{\Delta }\varphi$ correlation function in $40\%\text{–}60\%$ centrality of Pb-Pb collisions at $\sqrt{s}=2.76$ TeV from AMPT SM with proton (a) and pion (b) as trigger particles.

Figure 4

Centrality dependence of the near-side yield from the background subtracted correlation function. The yields from default version of AMPT have been multiplied by 1.5 for better visualization.

Figure 5

Ratio of proton trigger yield to pion trigger yield $\left(Y^p/Y^{\pi }\right)$ at high and intermediate $p_{T,\mathrm{trigger}}$ regions as indicated in the figure.

Figure 6

Ratio of proton trigger yield to pion trigger yield $\left(Y^p/Y^{\pi }\right)$ for Au+Au collisions at $\sqrt{(}s)=200$ AGeV, results from PHENIX [22] superposed.