We present results of 2-particle jet-like correlations, with high pT h+- triggers and identified pi+-, p, and pbar triggers in d+Au and Au+Au collisions and 3-particle jet-like azimuthal correlations in pp, d+Au, and Au+Au collisions at sqrt(s)=200 GeV. These results use data from the STAR TPC during RHIC runs II, III, and IV. Modifications in 2-particle correlations are observed in Au+Au collisions. These modifications are not seen in $pp$ or d+Au collisions. This demonstrates that the modifications are due to final state nuclear effects. High pT protons, anti-protons and charged pions are identified by the relativistic rise of dE/dx in the STAR TPC. Correlations of charged hadrons with high pT p, pbar, and pi+- show no discernible difference. The results post challenges to recombination and coalescence models which are otherwise very successful in explaining the large baryon/meson ratio and the splitting of the elliptic flow at intermediate pT. In central Au+Au collisions, the away-side 2-particle correlation is significantly broadened and even double humped in selective kinematic ranges. Three-particle correlations were employed to identify the underlying physics mechanism(s). Results in pp, d+Au and peripheral Au+Au collisions show dijet structure with away-side kT broadening. Results in mid-central and central Au+Au collisions are consistent with a near-side jet and on the away-side a combination of conical emission and large angle gluon radiation and deflected jets. The associated pT independent emission angle suggests Mach-cone shock waves being the underlying physics mechanism for the conical emission. The emission angle is measured to be 1.39+-0.01 (stat.)+-0.04(sys.) in ZDC triggered 0-12% Au+Au data.
Measurement of CollinearDrop jet mass and its correlation with SoftDrop groomed jet substructure observables in $\sqrt{s}=200$ GeV $pp$ collisions by STAR
Jets correlated with isolated photons are a promising channel to study jet quenching in heavy-ion collisions, as photons do not interact strongly and therefore constrain the $Q^2$ of the initial hard scattering. We present the isolated photon-jet correlations measured in Pb--Pb collisions at $\sqrt{s_{\text{NN}}}$ = 5.02 TeV by the ALICE collaboration. We study correlations of isolated photons above 20 GeV/$c$ with charged-particle jets above 10 GeV/$c$, reconstructed with the anti-$k_\text{T}$ algorithm. The correlations probe the lowest jet $p_\text{T}$ range ever measured at LHC energies, a…
Measurements of two-particle azimuthal angle correlations are a useful tool to study the distribution of jet energy loss, however, they are complicated because of the significant anisotropic flow background. We devise a data-driven method for subtracting anisotropic flow background in jet-like correlation analysis. We first require a large recoil momentum ($P_x$) within a given pseudo-rapidity ($η$) range from a high-transverse momentum particle to enhance in-acceptance population of away-side jet-like correlations. Then we take the difference of two-particle correlations in the close-region a…
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…
Early measurements at the Relativistic Heavy Ion Collider (RHIC) demonstrated jet quenching through the suppression of pairs of high momentum hadrons. These dihadron correlations have a large correlated background. As understanding of the background improved, it was recognized in the field that a significant term was omitted from the background and several dihadron correlation results were quantitatively and qualitatively incorrect. The original measurements demonstrating jet quenching have not been revisited. These measurements are repeated in this paper in a kinematic range similar to the or…
Jets of high energy collimated particles provide a rich phenomenology to study quantum chromodynamics, from first-principles tests of perturbative calculations to investigations of the emergent properties of the strongly-coupled quark-gluon plasma. In these proceedings, we highlight several recent jet measurements by the ALICE Collaboration, with a focus on jet substructure observables.
