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Quantitative Constraints on the Opacity of Hot Partonic Matter via high-p T p 0 suppression in

Quantitative Constraints on the Opacity of Hot Partonic Matter via high-p T p 0 suppression in Au+Au collisions at √ s NN = 200 GeV http://arxiv.org/abs/0801.1665 Jamie Nagle University of Colorado at Boulder for the PHENIX Collaboration. PHENIX.

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Quantitative Constraints on the Opacity of Hot Partonic Matter via high-p T p 0 suppression in

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  1. Quantitative Constraints on the Opacity of Hot Partonic Matter via high-pTp0 suppression in Au+Au collisions at √sNN = 200 GeV http://arxiv.org/abs/0801.1665 Jamie Nagle University of Colorado at Boulder for the PHENIX Collaboration PHENIX The PHENIX experiment has measured the suppression of semi-inclusive single high transverse momentum p0’s in Au+Au collisions at √sNN = 200 GeV. The present understanding of this suppression is in terms of energy-loss of the parent (fragmenting) parton in a dense color-charge medium. We have performed a quantitative comparison between various parton energy-loss models and our experimental data. The statistical point-to-point uncorrelated as well as correlated systematic uncertainties are taken into account in the comparison. We detail this methodology and the resulting constraint on the model parameters of medium opacity, as characterized via the initial color-charge density dNg/dy or the medium transport coefficient qhat. We find that high transverse momentum p0 suppression in Au+Au collisions has sufficient accuracy to constrain these model dependent opacity parameters at the ± 20–25% (1 standard deviation) level. These constraints include only the experimental uncertainties, and further studies are needed to compute the corresponding theoretical uncertainties. Extracting fundamental model-independent characteristics of the medium requires resolution of the differences in the model calculations. We utilize the following modified c2 function, that incorporates statistical uncorrelated uncertainties, point-to-point correlated systematic uncertainties, and completely correlated systematic uncertainties. ~ Full details of the statistical analysis are included in the paper. The resulting constraints on the models shown below are given in the Table at the one and two standard deviation uncertainty levels. We also include the constraints on a simple linear fit to the experimental data. PQM GLV WHDG We note that these model dependent parameters, in particular the range of large PQM qhat values is currently under intense theoretical debate Thus, the quoted constraints are for model-dependent parameters of the specific model implementation, and relating these parameters to the fundamental value of the mean transverse momentum squared exchange per unit length traversed and color-charge density may result in significantly different values. PQM: A. Dainese, C. Loizides, G. Paic, Eur. Phys. J C38: 461 (2005). C. Loizides, Eur. Phys. J.C49, 339 (2007) [hep-ph/0608133]. GLV: I. Vitev, Phys. Lett. B639, 38 (2006) [hep-ph/0603010]. M. Gyulassy, P. Levai, I. Vitev, Nucl. Phys. B571, 197 (2000) [hep-ph/9907461]. WHDG: W.A. Horowitz, S. Wicks, M. Djordjevic, M. Gyulassy,in preparation; S. Wicks, W. Horowitz, M. Djordjevic, M. Gyulassy, Nucl. Phys. A 783, 493 (2007) [nucl-th/0701063]; S. Wicks, W. Horowitz, M. Djordjevic,M. Gyulassy, Nucl. Phys. A 784, 426 (2007) [nucl-th/0512076]. ZOWW: H. Zhang, J.F. Owens, E. Wang, X-N Wang, Phys Rev. Lett. 98: 212301 (2007) [nucl-th/0701045]. ZOWW

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