Jet-like dihadron correlations in heavy ion collisions

Joshua R Konzer, Purdue University

Abstract

We probe jet production and jet/medium interplay using two dihadron correlation techniques: near-side jet-like isolation and Event Plane-trigger orientation dependence with distance and direction sensitivities. The near-side jet-like dihadron correlations compare and contrast d+Au and Au+Au data, as well as AMPT and HIJING simulations, in both Δη and Δ&phis; distributions from low (1.5-2.0 GeV) to high (6-10 GeV) trigger p T regions. High pT regions are dominated by jets and well described by perturbative QCD. Low p T regions should see significant influence due to soft processes in Au+Au data. Correlations are normalized by number of trigger particles and thus should manifest any flow effects at lower pT as a qualitative modification or dilution of strength in near-side distributions. Surprisingly, d+Au and Au+Au Δη and Δ&phis; near-side jet-like correlations show very similar yields and distributions, with slight differences in peak widths. The similarities are consistent throughout centrality, Event Plane orientation, and kinematic variances. On the other hand, neither AMPT and HIJING reproduce data. The results seem to challenge the current understanding of jet production mechanisms. Event Plane-trigger orientation dependent dihadron correlations including both distance and direction sensitivities have the potential to further the understanding of ridge production mechanisms, as well as away-side pathlength sensitivities. If the ridge is due to jet/medium flow alignment enhancing long range particle correlations, asymmetry of the ridge may show variance as a function of &phis;s=&phis;Trig. –ψEP. Likewise, the away-side jet-like peak may show differences due to the pathlength increasing as trigger orientation progresses from in-plane to out-of-plane. The resulting Δ&phis; distributions show significant asymmetry in the ridge, peaking at &phis;s ≈ 50°, whereas the jet remains constant. The away-side also shows &phis; s influence; starting as a single broad peak in-plane, progressing to two comparatively asymmetric peaks, and ending as two sharper symmetric peaks. Gaussian fits to the away-side peaks as a function of &phis; s support the possibility of an away-side ridge and the presence of two jet peaks with equal area, but different sigmas. These results suggest that the ridge is influenced by jet and medium flow alignment and away-side jet peaks are heavily influence by medium pathlength, but are not absorbed.

Degree

Ph.D.

Advisors

Wang, Purdue University.

Subject Area

Physics

COinS