STAR preliminary results of di-hadron correlations versus $ϕ_{s}$, the trigger particle azimuthal angle relative to the constructed event plane are reported for mid-central Au+Au collisions and compared to central Au+Au as well as minimum bias d+Au collisions. The correlations are observed to vary with $ϕ_{s}$ on both the near and away side of the trigger particle. The away-side correlation evolves from single- to double-peak with increasing $ϕ_{s}$. The near-side correlation is separated into 'jet' and 'ridge': the ridge is found to decrease with $ϕ_{s}$ while the jet remains relatively constant.
Angular correlations between charged trigger and associated particles are measured by the ALICE detector in p-Pb collisions at a nucleon-nucleon centre-of-mass energy of 5.02 TeV for transverse momentum ranges within 0.5 < $p_{\rm T}^{\rm assoc}$ < $p_{\rm T}^{\rm trig}$ < 4 GeV/$c$. The correlations are measured over two units of pseudorapidity and full azimuthal angle in different intervals of event multiplicity, and expressed as associated yield per trigger particle. Two long-range ridge-like structures, one on the near side and one on the away side, are observed when the per-trigger yield …
We obtain prompt di-photon cross-section in proton-nucleus collisions in Hamiltonian light-cone approach within a hybrid approximation, treating the projectile proton in the parton model and the target nucleus in the Color-Glass-Condensate approach. We study in details the di-photon correlations in quark-nucleus and proton-nucleus collisions at RHIC and the LHC. We show that the single fragmentation di-photon produces the away side correlations peak, and the double fragmentation component of prompt di-photon is responsible for the near-side peak, and the long-range in rapidity near-side azimut…
The first evidence of jet quenching was observed at RHIC via suppression of single high $p_T$ hadron $R_{AA}$ and the disappearance of the away-side jet peak in two-particle correlations. Since then, hadron $R_{AA}$ and two-particle correlations continue to be useful probes of the QGP in heavy ion collisions, since the particles involved are fragments of the jets produced in the initial hard scattering. PHENIX recently improved the width measurements extracted from $π^0$-hadron correlations after removing the higher order flow terms in the underlying event subtraction. Measurements of the away…
As a colorless probe, direct photons balance the $p_T$ of the away-side jet at leading order. Direct photon-hadron correlations are thus an excellent probe for nuclear structure and QCD effects, including parton energy loss in the Quark-Gluon Plasma. PHENIX has measured $π^{0}$ and direct photon-triggered two-particle azimuthal correlations in a variety of collision systems ranging from $p$$+$$p$ to Au+Au at 200 GeV. In $p$$+$Au and $d$$+$Au collisions, no modification of the per-trigger jet yield or away-side correlation width compared to $p$$+$$p$ collisions is observed for direct photon tri…
Direct photon-hadron correlations are a golden channel to study parton in-medium energy loss in QGP. The modification of the effective fragmentation function for the away-side jet can be measured by comparing integrated away-side yields of direct photon-hadron pairs in heavy ion collisions to those in p+p. We measured per-trigger-yield of associated hadrons in Au+Au collisions and observed that there is a suppression compared to p+p for higher momentum fraction ($z_T$) hadrons. This can be explained by the opacity of the hot medium: energetic partons from the initial hard scattering lose energ…
The similarity between small- and large-collision systems is explored using the charged-particle multiplicity in the transverse region, $N^{\rm T}_{\rm ch}$, which is sensitive to the underlying event. Measurements of charged-particle production as a function of $N^{\rm T}_{\rm ch}$ in pp, p-Pb and Pb-Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV in the toward, away and transverse regions are discussed. These three regions are defined relative to the track with the largest transverse momentum in the event ($p_{\rm T}^{\rm trig}$). The activity in the transverse region is subtracted from the ac…
The midrapidity $π^0$ nuclear modification factor, $R_{\rm{AA}}$, at $\sqrt{s_\mathrm{NN}} =$ 2.76 TeV in 6 centrality classes as well as the corresponding $π^0$ invariant yields in Pb-Pb and in pp collisions are presented. The transverse momentum range covered is 0.6 (0.4) GeV/$c$ $< p_{\mathrm{T}} <$ 12 (10) GeV/$c$ for Pb-Pb (pp) collisions. A suppression of neutral pions increasing with centrality is observed. The yield of charged particles associated with a high $p_{\mathrm{T}}$ neutral pion trigger (8 GeV/$c$ $< p_{\mathrm{T}} <$ 16 GeV/$c$) is measured in pp and Pb-Pb collisions at $\sq…
The yield of charged particles associated with high-$p_{\rm T}$ trigger particles ($8 < p_{\rm T} < 15$ GeV/$c$) is measured with the ALICE detector in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV relative to proton-proton collisions at the same energy. The conditional per-trigger yields are extracted from the narrow jet-like correlation peaks in azimuthal di-hadron correlations. In the 5% most central collisions, we observe that the yield of associated charged particles with transverse momenta $p_{\rm T}> 3$ GeV/$c$ on the away-side drops to about 60% of that observed in pp collisions, …
With our coupled jet-fluid model, we study the nuclear modifications of full jets and jet structures for single inclusive jet and $γ$-jet events in relativistic heavy-ion collisions. The evolution of full jet showers is studied via a set of coupled transport equations including the effects of collisional energy loss, transverse momentum broadening and medium-induced splitting. The dynamics of the jet energy and momentum deposited into the medium is described by hydrodynamic equations with source terms. Our detailed analysis indicates that collisional absorption (energy loss) tends to narrow th…
The discovery of correlations between particles separated by several units of pseudorapidity in high-multiplicity pp and p-Pb collisions, reminiscent of structures observed in Pb-Pb collisions, was a challenge to traditional ideas about collectivity in heavy ion collisions. In order to further explore long-range correlations and provide information to theoretical models, correlations between forward trigger muons and mid-rapidity associated hadrons were measured in p-Pb collisions at $\sqrt{s_{\mbox{NN}}} = 5.02~\mbox{TeV}$. The results demonstrate that the nearside and awayside ridges extend …
