Nuclear Physics & RIKEN Theory Seminar

"Questioning hydro at RHIC: Is it QCD all the way down?"

Presented by Tom Trainor, University of Washington

Friday, May 30, 2008, 2:00 pm — Small Seminar Room, Bldg. 510

Conventional analysis of RHIC data separates spectrum and correlation structure into three regimes: hard parton scattering and fragmentation described by pQCD (large pt), soft hadron production from a thermalized "partonic" medium described by hydro (small pt), and coalescence/recombination of "constituent quarks" from the flowing medium and from the parton fragment system (intermediate pt). Support for that picture is derived from the "blast-wave" spectrum model, "elliptic flow" measure v2 and "jet quenching" measure RAA. I review the standard conventions in the context of a "two-component" (soft + hard) model of spectra and correlations applied consistently over the full range of measured pt from 0.1 to 12 GeV/c. I relate the hard component, deduced from p-p spectra, to LEP fragmentation functions and the soft component to longitudinal nucleon fragmentation. I recast the RAA measure to a true ratio comparison of spectrum hard components (soft components are excluded). From v2(pt) data I reconstruct for the first time the spectra of identified "flowing" particles (quadrupole component) and show that the quadrupole is apparently unrelated to dramatic features of parton energy-loss systematics recently observed in spectra and angular correlations. I conclude that the quadrupole component is a small fraction of the total system and may represent a novel QCD radiation phenomenon. Hydrodynamic models and thermal equilibrium appear to be inconsistent with accurate descriptions of data.

Hosted by: Harmen Warringa

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