System size, energy, pseudorapidity, and centrality dependence of elliptic flow
journal contributionposted on 2008-04-14, 00:00 authored by B. Alver, B.B. Back, M.D. Baker, M. Ballintijn, D.S. Barton, R.R. Betts, A.A. Bickley, R. Bindel, W. Busza, A. Carroll, Z. Chai, V. Chetluru, M.P. Decowski, E. Garcia, T. Gburek, N. George, K. Gulbrandsen, C. Halliwell, J. Hamblen, I. Harnarine, M. Hauer, C. Henderson, D.J. Hofman, R.S. Hollis, R. Holynski, B. Holzman, A. Iordanova, E. Johnson, J.L. Kane, N. Khan, P. Kulinich, C.M. Kuo, W. Li, W.T. Lin, C. Loizides, S. Manly, A.C. Mignerey, R. Nouicer, A. Olszewski, R. Pak, C. Reed, E. Richardson, C. Roland, G. Roland, J. Sagerer, H. Seals, I. Sedykh, C.E. Smith, M.A. Stankiewicz, P. Steinberg, G.S.F. Stephans, A. Sukhanov, A. Szostak, M.B. Tonjes, A. Trzupek, C. Vale, G.J. Van Nieuwenhuizen, S.S. Vaurynovich, R. Verdier, G.I. Veres, P. Walters, E. Wenger, D. Willhelm, F.L.H. Wolfs, B. Wosiek, K. Wozniak, S. Wyngaardt, B. Wyslouch
This Letter presents measurements of the elliptic flow of charged particles as a function of pseudorapidity and centrality from Cu-Cu collisions at 62.4 and 200 GeV using the PHOBOS detector at the Relativistic Heavy Ion Collider. The elliptic flow in Cu-Cu collisions is found to be significant even for the most central events. For comparison with the Au-Au results, it is found that the detailed way in which the collision geometry (eccentricity) is estimated is of critical importance when scaling out system-size effects. A new form of eccentricity, called the participant eccentricity, is introduced which yields a scaled elliptic flow in the Cu-Cu system that has the same relative magnitude and qualitative features as that in the Au-Au system.