A first look at Au+Au collisions at RHIC energies using the PHOBOS detector

Birger Back, M. D. Baker, D. S. Barton, R. R. Betts, R. Bindel, A. Budzanowski, W. Busza, A. Carroll, J. Corbo, M. P. Decowski, E. Garcia, N. George, K. Gulbrandsen, S. Gushue, C. Halliwell, J. Hamblen, G. A. Heintzelman, C. Henderson, D. Hicks, D. J. HofmanR. Hollis, R. Holyński, B. Holzman, A. Iordanova, E. Johnson, J. L. Kane, J. Katzy, N. Khan, W. Kucewicz, P. Kulinich, C. M. Kuo, W. T. Lin, S. Manly, D. McLeod, J. Michalowski, A. C. Mignerey, J. Mülmenstädt, R. Nouicer, A. Olszewski, R. Pak, I. C. Park, H. Pernegger, M. Rafelski, M. Rbeiz, C. Reed, L. P. Remsberg, M. Reuter, C. Roland, G. Roland, L. Rosenberg, J. Sagerer, P. Sarin, P. Sawicki, W. Skulski, S. G. Steadman, P. Steinberg, G. S.F. Stephans, M. Stodulski, A. Sukhanov, J. L. Tang, R. Teng, A. Trzupek, C. Vale, G. J. Van Nieuwenhuizen, R. Verdier, B. Wadsworth, F. L.H. Wolfs, B. Wosiek, K. Woźniak, A. H. Wuosmaa, B. Wyslouch

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The PHOBOS detector has been used to study Au + Au collisions at √SNN = 56, 130, and 200 GeV. Several global observables have been measured and the results are compared with theoretical models. These observables include the charged-particle multiplicity measured as a function of beam energy, pseudo-rapidity, and centrality of the collision. A unique feature of the PHOBOS detector is its almost complete angular coverage such that these quantities can be studied over a pseudo-rapidity interval of |η| ≤ 5.4. This allows for an almost complete integration of the total charged particle yield, which is found to be about Nchtot = 4200 ± 470 at √SNN = 130 GeV and Nchtot = 5300 ± 530 at √SNN = 200 GeV. The ratio of anti-particles to particles emitted in the mid-rapidity region has also been measured using the PHOBOS magnetic spectrometer. Of particular interest is the ratio of anti-protons to protons in the mid-rapidity region, which was found to be p̄/p = 0.6 ± 0.04(stat) ± 0.06(syst) at √SNN = 130 GeV. This high value suggests that an almost baryon-free region has been produced in the collisions.

Original languageEnglish
Pages (from-to)921-931
Number of pages11
JournalPramana - Journal of Physics
Issue number5
StatePublished - May 2003
EventProceedings of the International Conference on Physics and Astrophysics of Quark-Gluon Plasma - Part II - Jaipur, India
Duration: 26 Nov 200130 Nov 2001


  • Charged particle multiplicity
  • Ultra-relativistic heavy-ion collisions


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