Steffen Bass
Duke University

Abhijit Majumder
Wayne State University

Joern Putschke
Wayne State University

Lijuan Ruan
Brookhaven National Laboratory

Program Coordinator:
Farha Habib
(206) 685-4286

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INT Program INT-17-1b
Precision Spectroscopy of QGP Properties with Jets and Heavy Quarks

May 1 - June 8, 2017


Data taken at the Relativistic Heavy Ion Collider (RHIC) over the last decade have shown conclusively that the high temperature phase of QCD matter is a Quark-Gluon Plasma (QGP) with the characteristics of a "nearly perfect" liquid. This conclusion has been confirmed by measurements in Pb+Pb collisions at much higher energy at the CERN Large Hadron Collider (LHC). In addition to the nearly inviscid liquid behavior of the QGP, the RHIC and LHC experiments have shown that the QGP is highly opaque to energetic partons, resulting in "strong jet quenching". The physics goal for the next decade is to characterize the properties of this quark-gluon plasma liquid by quantitative extraction of fundamental medium parameters from precision measurements of sensitive observables, including for example hadron spectra, angular distributions and correlations, jet observables, heavy quarks and electromagnetic probes.

This program will focus on the utilization of jets and heavy-quarks as probes of the QGP, since these are the two areas with significant progress in recent years in terms of experimental capabilities and improvements in theoretical tools. Both, jets and heavy quarks, are hard probes that are being produced early on in the time-evolution of heavy-ion collisions in processes that are well described using perturbative QCD. They interact strongly with the surrounding QGP medium, and their measurable modifications in the final state distributions with respect to vacuum expectations yield significant information on the properties of the QGP medium. Of particular interest are the QGP transport coefficients, such as the jet energy-loss parameters q̂ and ê as well as the heavy quark diffusion coefficients D. All of these quantities are thought to exhibit a non-trivial temperature dependence, the extraction of which will require high-precision data and advances in theory that are currently under development. Since hard processes probe the QGP over a wide range of length scales this program will also explore their use for determining the microscopic nature of the QGP as well as the transition from weakly to strongly coupled parton energy loss.

The goal of the program is to bring together experts in the areas of of jet production, energy- loss and heavy-quark dynamics to assess the progress made in utilizing these probes for the characterization of the properties of the QGP medium, as well as to expose and bring into focus unresolved questions and open issues that should be addressed via new theory efforts or experimental measurements.

Key Topics

Key topics to be addressed include:
  • survey of latest measurements at RHIC and LHC of
    • open heavy flavor (D mesons, electrons,muons)
    • heavy quarkonia (J/ψ, ψ(2S), ϒ(1S; 2S; 3S))
    • jets and leading high-pT hadrons
    • p(d)A jet measurements, energy loss in small QGP droplets
  • theory of jet evolution in the QGP medium
    • range of applicability for different calculational schemes
    • leading particle observables vs. full jets
    • hadronic final state interactions: relevant or negligible?
    • sensitivity of hard probe theory calculations to the underlying QGP medium: what medium features can be reliably probed?
  • heavy-flavor dynamics in medium
  • comprehensive analysis: do jets and heavy quarks provide a consistent picture?
  • initial state and saturation physics - how important for hard probes?
  • future roadmap: what are the most essential measurements and theory advances to be undertaken?

Goals and Expected Outcomes

The goal of this program is twofold: (1) to educate young scientists in the state of the art of jet and heavy quark physics as it pertains to the extraction of QGP properties and (2) to review our current knowledge in that sector and develop a roadmap on how best to utilize the newly available high quality data and novel theory advances for the high precision extraction of QGP properties in the near to medium term future as well as how to utilize the complementary of RHIC and LHC jet measurements in the longer term future enabled by proposed experimental upgrades at RHIC.

Program Format

Individual program weeks will be devoted to specific topics, with a comprehensive overarching workshop scheduled for the 2nd week of the program. In order to provide sufficient time for discussion during the regular program weeks, two seminar-style presentations will be given per day (in the morning) as well as a daily discussion session to follow up on topics and presentations as the need arises (in the afternoon). Depending on participant interest, the program in week #6 might be converted into a workshop-style setup.

  • Week 1: Heavy Quarks in QCD matter
  • Week 2: Workshop
  • Week 3: Jet energy loss theory
  • Week 4: Monte-Carlo approaches to Jet energy-loss
  • Week 5: Onia
  • Week 6: comprehensive picture & future of the field
Please note that a workshop registration fee of $45 will apply for attending the second week of the program.