Constraints on jet quenching in p–Pb collisions at sNN=5.02 TeV measured by the event-activity dependence of semi-inclusive hadron-jet distributions

Direct real photons in relativistic heavy ion collisions

“…One way to circumvent the bias is to categorize events according to the experimentally measured "event activity" rather than the model-calculated "centrality" (this path has been adopted by the ALICE experiment, see for instance [209,210]). This is not just a question of semantics.…”

Early time dynamics and hard probes in heavy-ion collisions (theory)

“…Despite all the complications associated with the study of hard probes in small systems, experiments are starting to provide stringent constrains, e.g. on the energy loss of reconstructed jets [23], and preliminary studies based on fluid-dynamical + jet simulations [24,25], hint at sizable effects in high-multiplicity events. However, there are currently no dedicated theoretical studies combining the out-of-equilibrium dynamics of soft and hard degrees of freedom and the key question, to what extent hard probes can serve as control measurement to constrain the bulk dynamics in small systems will require further investigations in the future.…”

Correlations of High-pT Hadrons and Jets in ALICE

“…The same analysis procedure will be then applied to the data from p-Pb collisions at √ s NN = 5.02 TeV from 2013. Further details about both data sets and analyses can be found in the original papers [14,15]. ALICE is one of the four big experiments working at the Large Hadron Collider at CERN.…”

“…The detection of a high-p T jet at midrapidity affects measurement of event activity or "centrality" in forward rapidity, and the assigned event geometry can be biased. Hadron-jet coincidence observables have the advantage that they can be used to identify jet quenching without the need to know the corresponding nuclear overlap function [15]. If there were no medium-induced modifications of jet production in p-Pb, cross sections appearing on the right-hand side of (5) could be expressed in terms of the corresponding pp cross sections and the the nuclear…”

“…The ratio is independent of jet p T and can be used to extracts provided that the ratio and the slope parameter b are extracted from data. Thus from the data in Figures 3 and 4, the following estimates for the spectrum shift were obtained [15]:s = (−0.12 ± 0.35 stat ± 0.03 syst ) GeV/c for events where event activity was measured by ZNA, ands = (−0.06 ± 0.34 stat ± 0.02 syst ) GeV/c for events where event activity was measured by V0A. Both values are consistent with zero within uncertainties.…”