Centrality and sNNDependenceofthe\sqrt{s_{NN}} Dependence of the dE_{T}/d\etaand and dN_{ch}/d\eta$ in Heavy Ion Collisions at Mid-Rapidity

The PHENIX experiment at RHIC has measured transverse energy and charged particle multiplicity at mid-rapidity in Au + Au collisions at $\sqrt{s_{NN}}$ = 19.6, 130, 62.4 and 200 GeV as a function of centrality. The presented results are compared to measurements from other RHIC experiments, and experiments at lower energies. The $\sqrt{s_{NN}}$ dependence of $dE_{T}/d\eta$ and $dN_{ch}/d\eta$ per pair of participants is consistent with logarithmic scaling for the most central events. The centrality dependence of $dE_{T}/d\eta$ and $dN_{ch}/d\eta$ is similar at all measured incident energies. At RHIC energies the ratio of transverse energy per charged particle was found independent of centrality and growing slowly with $\sqrt{s_{NN}}$. A survey of comparisons between the data and available theoretical models is also presented.Comment: Proccedings of the Workshop: Focus on Multiplcity at Bari, Italy, June 17-19,2004. To be submitted to the Jornal of Physics, "Conference series". Includes: 20 Pages, 15 figures, 3 Tables, 80 Referencie

Rapidity and k_T dependence of HBT correlations in Au+Au collisions at 200 GeV with PHOBOS

Two-particle correlations of identical charged pion pairs from Au+Au collisions at sqrt(s_NN) = 200 GeV were measured by the PHOBOS experiment at RHIC. Data for the most central (0--15%) events were analyzed with Bertsch-Pratt (BP) and Yano-Koonin-Podgoretskii (YKP) parameterizations using pairs with rapidities of 0.4 < y < 1.3 and transverse momenta 0.1 < k_T < 1.4 GeV/c. The Bertsch-Pratt radii decrease as a function of pair transverse momentum. The pair rapidity Y_pipi roughly scales with the source rapidity Y_YKP, indicating strong dynamical correlations.Comment: 5 pages, 2 figures. To appear in the proceedings of Seventeenth International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions (Quark Matter 2004), Oakland, California from January 11-17, 2004. Submitted to Journal of Physics G: Nuclear and Particle Physic

Pseudorapidity Distributions of Charged Particles in d + Au and p + p Collisions at sNN\sqrt{s_{_{NN}}} = 200GeV

The measured pseudorapidity distributions of primary charged particles are presented for d + Au and p + p collisions at ${\sqrt{s_{_{NN}}} =}$ 200 GeV over a wide pseudorapidity range of ${\rm \mid \eta \mid \le}$ 5.4. The results for d + Au collisions are presented for minimum-bias events and as a function of collision centrality. The measurements for p + p collisions are shown for minimum-bias events. The ratio of the charged particle multiplicity in d + Au and p + A collisions relative to that for inelastic p + p collisions is found to depend only on ${}$, and it is remarkably independent of collision energy and system mass. The deuteron and gold fragmentation regions in d + Au collisions are in good agreement with proton nucleus data at lower energies.Comment: 4 pages, 3 figures. To appear in the proceedings of Seventeenth International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions (Quark Matter 2004), Oakland, California from January 11-17, 2004. Submitted to Journal of Physics G: Nuclear and Particle Physic

The Landscape of Particle Production: Results from PHOBOS

Recent results from the PHOBOS experiment at RHIC are presented, both from Au+Au collisions from the 2001 run and p+p and d+Au collisions from 2003. The centrality dependence of the total charged particle multiplicity in p+p and d+Au show features, such as Npart-scaling and limiting fragmentation, similar to p+A collisions at lower energies. Multiparticle physics in Au+Au is found to be local in (pseudo)rapidity, both when observed by HBT correlations and by forward-backward pseudorapidity correlations. The shape of elliptic flow in Au+Au, measured over the full range of pseudorapidity, appears to have a very weak centrality dependence. Identified particle ratios in d+Au reactions show little difference between the shape of proton and anti-proton spectra, while the absolute yields show an approximate m_T scaling.Comment: 8 Pages, 11 Figures, Plenary talk at Quark Matter 2004, Oakland, CA, January 11-18, 200

GLOBAL OBSERVATIONS FROM PHOBOS.

Particle production in Au+Au collisions has been measured in the PHOBOS experiment at RHIC for a range of collision energies. Three empirical observations have emerged from this dataset which require theoretical examination. First, there is clear evidence of limiting fragmentation. Namely, particle production in central Au + Au collisions, when expressed as dN/d{eta}{prime} ({eta}{prime} {triple_bond} {eta} - y{sub beam}), becomes energy independent at high energy for a broad region of {eta}{prime} around {eta}{prime} = 0. This energy-independent region grows with energy, allowing only a limited region (if any) of longitudinal boost-invariance. Second, there is a striking similarity between particle production in e{sup +}e{sup -} and Au + Au collisions (scaled by the number of participating nucleon pairs). Both the total number of produced particles and the longitudinal distribution of produced particles are approximately the same in e{sup +}e{sup -} and in scaled Au + Au. This observation was not predicted and has not been explained. Finally, particle production has been found to scale approximately with the number of participating nucleon pairs for &lt;N{sub part}&gt; &gt; 65. This scaling occurs both for the total multiplicity and for high p{sub T} particles (3 &lt; p{sub T} &lt; 4.5 GeV/c)