CERP2010
April 14–17, 2010
Austin, Texas, U.S.A.
published March 01, 2011
Austin, Texas, U.S.A.
published March 01, 2011
The intent of this workshop is to bring together knowledgeable advocates for the major physics interpretations of RHIC data, both theoretical and experimental, as well as members of the high energy physics community, in order to examine critically the strengths and weaknesses of each of the following paradigms and to formulate methods to resolve conflicting interpretations of data. Three major paradigms have emerged in the RHIC community for understanding the more-central A-A collisions. Advocates offer the following general interpretations of the heavy-ion collision system at RHIC:
A) Chemical and Thermal Equilibration - Hydrodynamics: An estimate of four-volume of the partonic phase produced in Au-Au collisions at RHIC is 800 fm4, i.e. vastly greater than in elementary interactions. During the evolution of the system the material in this macroscopic volume is close to a second-order phase transition, and consequently the dynamics is strongly coupled. The strong elliptic flow together with viscous hydrodynamics simulations indicate that the shear viscosity to entropy ratio is
within a factor of a few of the AdS/CFT bound, 1/(4pi). It is difficult to reconcile this observation with a quasi-particle picture. In addition, the baryon and meson elliptic flows are explained naturally in the hydrodynamic framework by allowing for multiple relaxation times.
B) Hadronization via Recombination: Similar to the spirit of the old parton model the quark-gluon plasma at hadronization can be described as an ensemble of quarks coalescing into hadrons in a simple recombination process. There is ample experimental evidence from scaling laws for the 2→1 and 3→1 kinematics of the coalescence. Knowledge of these scaling laws allows us to extrapolate back to the quark phase in a straightforward way, naturally leading to a picture of collectively moving partons in the plasma phase.
C) Perturbative QCD and Fragmentation: A surprisingly large fraction of produced hadrons can be described with a modified pQCD approach. Even for central Au-Au collisions strong jet correlations observed at small parton energy scales and hadron momenta contradict parton absorption in an opaque medium and hadron re-scattering. Initial-state nucleon and parton scattering appear to lead directly to fragmentation and hadronization. Most initial-state scattered partons produce final-state jets without rescattering. With linear superposition of N-N collisions as the reference, modest deviations in A-A collisions may reveal new QCD phenomena.
The nominal purpose of the workshop is to present central aspects of the above paradigms with supporting evidence and significant alternative viewpoints and to explore methods for paradigm testing and resolution of contradictions. We wish to bring together current experts in theory and experiment to refine paradigm descriptions and evaluate theoretical arguments, supporting/contradictory experimental evidence, and analysis techniques.
| Wed. April 14 morning session, "Recombination vs Fragmentation" Chairperson: Denes Molnar |
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"Hadrons from quarks, gluons and first principles"
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"Review of particle spectrum data"
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"Parton fragmentation in nuclear collisions"
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"Recombination in nuclear collisions"
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| Wed. April 14 afternoon session, "Recombination vs Fragmentation" Chairperson: Mike Tannenbaum |
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"Elliptic flow: A survey"
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"RHIC paradigms: Early thermalization and collectivity—are they achieved in RHIC’s new state of matter?"
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"Strings, jets and quark coalescence in transport models"
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"Quark recombination in heavy ion collisions"
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| Wednesday Q&A |
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"Discussion on coalescence vs fragmentation, hadronization mechanisms and their effects on the observed final state"
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Wednesday Question and Answer Transcripts
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| Thur. April 15 morning session, "Hydrodynamics vs Semi-Hard Jets - Minijets" Chairperson: Thorsten Renk |
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"Hydrodynamics at RHIC (ideal and viscous): Where it works, where and how it breaks down, and why"
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"The azimuth quadrupole in nuclear collisions"
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"From the ridges and jet v2 to magnetic plasma"
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"Review of minimum-bias jet systematics at RHIC"
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| Thur. April 15 afternoon session, "Hydrodynamics vs Semi-Hard Jets - Minijets" Chairperson: Boris Kopeliovich |
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"Dissecting the hydro paradigm"
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"Do two-dimensional correlation data falsify RHIC paradigms?"
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"Dissipative corrections to spectra and v2 at large momentum"
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| Thursday Q&A |
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"Discussion on initial conditions, minijet survival, quadrupole vs minijet systematics"
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Thursday Question and Answer Transcripts
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| Fri. April 16 morning session, "High pt Spectra, Jets and pQCD" Chairperson: Rudy Hwa |
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"Critical examination of RHIC paradigms - mostly high pt"
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"Can we make sense of the correlation data at RHIC?"
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"Is jet quenching perturbative — why we see mainly unmodified probes and where to look for interesting things"
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"Jet reconstruction — understanding the backgrounds and biases is key"
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| Fri. April 16 afternoon session, "High pt Spectra, Jets and pQCD" Chairperson: Charles Chiu |
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"Positive progress from hard scattering"
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"Experimental review of high-pt phenomena at mid-rapidity at RHIC"
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"High-pt paradigms revisited"
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"Jet properties from dihadron correlations — from RHIC to LHC"
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| Friday Q&A |
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"Discussion on jet and spectrum structure vs pQCD from high pt down to the soft sector"
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Friday Question and Answer Transcripts
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| Sat. April 17 morning session, "High Energy Physics Perspectives for RHIC" Chairperson: Yuri Dokshitzer |
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"Azimuthal correlation between jets and ridges"
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"How strong is the strong coupling constant in Au+Au at RHIC?"
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"How well can we treat energy loss and hydrodynamics?"
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"Hydro paradigm and covariant transport"
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| Saturday Q&A |
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"Closing discussion with brief comments"
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Saturday Question and Answer Transcripts
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