System size, energy and pseudorapidity dependence of directed and elliptic flow at RHIC

PHOBOS measurements of elliptic flow are presented as a function of pseudorapidity, centrality, transverse momentum, energy and nuclear species. The elliptic flow in Cu-Cu is surprisingly large, particularly for the most central events. After scaling out the geometry through the use of an alternative form of eccentricity, called the participant eccentricity, which accounts for nucleon position fluctuations in the colliding nuclei, the relative magnitude of the elliptic flow in the Cu-Cu system is qualitatively similar to that measured in the Au-Au system.Comment: Presented at the 18th International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions in Budapest, Hungary, Aug. 4-9, 200

Vertex Reconstruction Using a Single Layer Silicon Detector

Typical vertex finding algorithms use reconstructed tracks, registered in a multi-layer detector, which directly point to the common point of origin. A detector with a single layer of silicon sensors registers the passage of primary particles only in one place. Nevertheless, the information available from these hits can also be used to estimate the vertex position, when the geometrical properties of silicon sensors and the measured ionization energy losses of the particles are fully exploited. In this paper the algorithm used for this purpose in the PHOBOS experiment is described. The vertex reconstruction performance is studied using simulations and compared with results obtained from real data. The very large acceptance of a single-layered multiplicity detector permits vertex reconstruction for low multiplicity events where other methods, using small acceptance subdetectors, fail because of insufficient number of registered primary tracks.Comment: accepted for publication in Nucl. Instr. Meth.

Charged Particle Multiplicities in Ultra-relativistic Au+Au and Cu+Cu Collisions

The PHOBOS collaboration has carried out a systematic study of charged particle multiplicities in Cu+Cu and Au+Au collisions at the Relativistic Heavy-Ion Collider (RHIC) at Brookhaven National Laboratory. A unique feature of the PHOBOS detector is its ability to measure charged particles over a very wide angular range from 0.5 to 179.5 deg. corresponding to |eta|<5.4. The general features of the charged particle multiplicity distributions as a function of pseudo-rapidity, collision energy and centrality, as well as system size, are discussed.Comment: Proceedings of "Lake Louise Winter Institute 2006", Lake Louise, Alberta, Canada, February 17-23, 2006, World Scientific 5 pages, 3 figure

'Sociologists Talking'

[No abstract][No keywords]

MESHING NATURAL RESOURCE USE AND DEVELOPMENT WITH INCREASING URBANIZATION

Resource /Energy Economics and Policy,

Bulk hadron production at high rapidities

Recent experimental observations on the `bulk' features of particle production at high (pseudo)rapidities will be reviewed. This kinematic region is of interest mostly because of its relevance to the theoretical description of initial state effects of nuclei at ultra-relativistic energies. Measurements of the charged hadron multiplicity density as well as the pseudorapidity dependence of the elliptic and directed flow exhibit a remarkable scaling property as a function of collision energy. This scaling seems to hold for pions and even photons and J/Psi-s, but is violated for protons. The special role of baryons will be discussed using selected results on nuclear transparency and baryon stopping.Comment: 10 pages, 8 figures. Prepared for the Proceedings of the Quark Matter 2005 Conferenc