Azimuthal Anisotropy of pi(0) Production in Au plus Au Collisions at root s(NN)=200 GeV: Path-Length Dependence of Jet Quenching and the Role of Initial Geometry

Adare, Andrew
Hill, John
Ogilvie, Craig
Kempel, Todd
Lajoie, John
Lebedev, Alexandre
Ogilvie, Craig
Pei, H.
Rosati, Marzia
Semenov, Alexey
Vale, Carla
Wei, Feng
et al.
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We have measured the azimuthal anisotropy of pi(0) production for 1 < p(T) < 18 GeV/c for Au + Au collisions at root s(NN) = 200 GeV. The observed anisotropy shows a gradual decrease for 3 less than or similar to p(T) less than or similar to 7-10 GeV/c, but remains positive beyond 10 GeV/c. The magnitude of this anisotropy is underpredicted, up to at least similar to 10 GeV/c, by current perturbative QCD (PQCD) energy-loss model calculations. An estimate of the increase in anisotropy expected from initial-geometry modification due to gluon saturation effects and fluctuations is insufficient to account for this discrepancy. Calculations that implement a path-length dependence steeper than what is implied by current PQCD energy-loss models show reasonable agreement with the data.

<p>This article is published as Adare, A., S. Afanasiev, C. Aidala, N. N. Ajitanand, Y. Akiba, H. Al-Bataineh, J. Alexander et al. "Azimuthal Anisotropy of π 0 Production in Au+ Au Collisions at s N N= 200 GeV: Path-Length Dependence of Jet Quenching and the Role of Initial Geometry." <em>Physical review letters</em> 105, no. 14 (2010): 142301. DOI:<a href="" target="_blank">10.1103/PhysRevLett.105.142301</a>. Posted with permission.</p>