|
Author(s)
|
Roland, G ; Back, B B ; Baker, M D ; Barton, D S ; Betts, R R ; Bindel, R ; Budzanowski, A ; Busza, W ; Carroll, A ; Decowski, M P ; García, E ; George, N ; Gulbrandsen, K H ; Gushue, S ; Halliwell, C ; Hamblen, J ; Heintzelman, G A ; Henderson, C ; Holynski, R ; Hofman, D J ; Holzman, B ; Johnson, E ; Kane, J L ; Katzy, J M ; Khan, N ; Kucewicz, W ; Kulinich, P A ; Lin, W T ; Manly, S L ; McLeod, D ; Michalowski, J ; Mignerey, A C ; Mülmenstädt, J ; Nouicer, R ; Olszewski, A ; Pak, R ; Park, I C ; Pernegger, H ; Reed, C ; Remsberg, L P ; Reuter, M ; Roland, C ; Roland, G ; Rosenberg, L J ; Sarin, P ; Sawicki, P ; Skulski, W ; Steadman, S G ; Stephans, G S F ; Steinberg, P ; Stodulski, M ; Sukhanov, A ; Tang, J L ; Teng, R ; Trzupek, A ; Vale, C ; van Nieuwenhuizen, G J ; Verdier, R ; Wadsworth, B ; Wolfs, F L H ; Wosiek, B ; Wozniak, K ; Wuosmaa, A H ; Byslouch, B |
|
Abstract
| During the first run of RHIC, the PHOBOS experiment recorded Au+Au collisions at square root (S/sub NN/) of 56 GeV and 130 GeV. These data have allowed us-to study. the, energy and centrality dependence of particle production, the anisotropy of the final state azimuthal distribution and particle-ratios at mid-rapidity. Our results show a non-trivial evolution of particle densities with both centrality and collision energy reaching significantly higher values per participating nucleon than at lower energies or in nucleon-nucleon collisions. At square root (S/sub NN/)=130 GeV we observe 4100+or-100 (stat.)+or-400(stat.) charged particles with \eta < 5.4 for the 3% most central collisions. The observed strong event anisotropy of v /sub 2//sup max/>0.06, beyond the value predicted in hadronic cascade models, indicates a closer approach to local thermal equilibration than at lower collision energies. The data on particle ratios show that at square root (S/sub NN/)=130 GeV a significant fraction of the incoming baryon number is still shifted towards mid-rapidity. Nevertheless, the resulting baryochemical potential mu /sub B/ of about 45 MeV is a factor of 5-6 lower than at SPS energies. |