Event-by-EventHydrodynamics+JetEnergy Loss: A Solution to theRAA⊗v

Abstract

High pT > 10 GeV elliptic flow, which is experimentally measured via the correlation between soft and hard hadrons, receives competing contributions from event-by-event fluctuations of the low pT elliptic flow and event plane angle fluctuations in the soft sector. In this paper, a proper account of these event-by-event fluctuations in the soft sector, modeled via viscous hydrodynamics, is combined with a jet energy loss model to reveal that the positive contribution from low pT v2 fluctuations overwhelms the negative contributions from event plane fluctuations. This leads to an enhancement of high pT > 10 GeV elliptic flow in comparison to previous calculations and provides a natural solution to the decade long high pT RAA ⌦ v2 puzzle. We also present the first theoretical calculation of high pT v3, which is shown to be compatible with current LHC data. Furthermore, we discuss how short wavelength jet-medium physics can be deconvoluted from the physics of soft, bulk event-by-event flow observables using event shape engineering techniques.

Event-by-event correlations between soft hadrons and D0 mesons in 5.02 TeV PbPb collisions at the CERN Large Hadron Collider

“…This qualitative understanding has been recently confirmed by the first jet energy loss + event-by-event viscous hydrodynamic calculations performed in [17,18]. A novel feature found in [17,18] is that the approximate linear response between v 2 and ε 2 also holds at high p T on an event-by-event basis.…”

“…This qualitative understanding has been recently confirmed by the first jet energy loss + event-by-event viscous hydrodynamic calculations performed in [17,18]. A novel feature found in [17,18] is that the approximate linear response between v 2 and ε 2 also holds at high p T on an event-by-event basis. This implies that the quantum randomness in the position of the nucleons in the incident nuclei, which determines the fluctuations of the initial conditions used in the subsequent hydrodynamic evolution, significantly affects the distribution of path lengths traversed by jets in the medium.…”

“…We generate hydrodynamic profiles using the 2D+1 event-by-event relativistic viscous hydrodynamical model, v-usphydro [44][45][46], which passes standard accuracy tests [47]. Our setup is the same as [17,46] η/s = 0.05, and initial time τ 0 = 0.6 fm), which describes experimental data in the soft sector, such that all the hydrodynamic parameters are fixed in the present study. The heavy quarks are evolved on top of hydrodynamic backgrounds until they reach the jet-medium decoupling temperature T d below which hadronization is performed using the Peterson fragmentation function [51].…”

Jet Tomography in Heavy-Ion Collisions—Challenges, Results, and Open Problems

“…For SHEE [63], we coupled the (hydrodynamic) v-USPhydro code [64,65] to the BBMG model. 15,000 Glauber initial conditions are generated and three different events are selected:…”

Flow and correlation phenomena measurements in pp, pPb and PbPb collisions at CMS

“…In Fig. 1 left panel, the v 2 and v 3 results are compared to the CUJET3.0 [9] and SHEE [8] models for several centrality bins. An essencial difference between these two models is that in SHEE is that it includes initial-state geometry fluctuations (in addition to linear path-length dependence of parton energy loss), whereas CUJET3.0 uses a smooth hydrodynamic background (and uses perturbative quantum chromodynamics (pQCD) calculations to describe the hard parton interactions).…”