Abstract
We calculate the jet shape and the jet cross section in heavy ion collisions using soft-collinear effective theory (SCET) and its extension with Glauber gluon interactions in the medium (SCET$_{\rm G}$). We use the previously developed framework to systematically resum the jet shape at next-to-leading logarithmic accuracy, and we consistently include the medium modification by incorporating the leading order medium-induced splitting functions. The calculation provides, for the first time, a quantitative understanding of the jet shape modification measurement in lead-lead collisions at $\sqrt{s_{\rm NN}}=2.76$ TeV at the LHC. The inclusive jet suppression is also calculated within the same framework beyond the traditional concept of parton energy loss, and the dependence on the centrality, the jet radius and the jet kinematics is examined. In the end we present predictions for the anticipated jet shape and cross section measurements in lead-lead collisions at $\sqrt{s_{\rm NN}}\approx5.1$ TeV at the LHC.
Highlights
The jet shape modification measurement in lead-lead collisions at sNN = 2.76 TeV at the LHC
Even though the production cross section of jets associated with prompt photons is several orders of magnitude smaller than the inclusive jet cross section, photon+jet events give a clean probe of the medium because the prompt photon can be used as a robust reference to study the quenching of the recoiling jet [21]
We find that the final state jet-medium interaction alone is not sufficient to describe the suppression of the cross section at high transverse momenta, and the inclusion of cold nuclear matter (CNM) effects with μCNM = 0.35 GeV provides a good description of the experimental data
Summary
Accurate QCD calculations provide robust theory control of jet physics [61,62,63] They have allowed one of the most precise extraction of the strong coupling constant [64,65,66,67,68]. Because of the huge underlying event background, a small radius is usually chosen in jet reconstruction. This leads to the significant suppression of the jet cross section because the radiation can be lost outside jets. Because of the sensitivity to physics at multiple energy scales, the theoretical calculations of jet substructure observables are challenging tasks, which has been realized for a long time. The resummation of the perturbative series becomes necessary, and the medium modification of jet substructure observables will have to be consistently included
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