29,525 research outputs found
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.
Particle production at very low and intermediate transverse momenta in d+Au and Au+Au collisions
The transverse momentum spectra of identified charged particles have been
measured at very low and intermediate transverse momenta in Au+Au collisions at
sqrt(s_NN) = 62.4 GeV and d+Au collisions at sqrt(s_NN) = 200 GeV using the
PHOBOS detector at RHIC. New results on charged particle production at very low
p_T in central Au+Au collisions at sqrt(s_{NN) = 200 GeV in the centrality
intervals 0-6% and 6-15% are presented. A comparison of the PHOBOS low-p_T data
with predictions of a recent optical model is shown. The shapes of m_T spectra
for d+Au and Au+Au collisions are compared.Comment: Presented at the 18th International Conference on Ultra-Relativistic
Nucleus-Nucleus Collisions, Quark Matter 2005, Budapest, Hungary, Aug. 4-9,
200
Heavy ion collisions in the used nucleon model
It is shown that recently proposed by R.J. Glauber the used nucleon model
combined with the assumption that the nucleon consists of two constituents (a
quark and a diquark) describes well the PHOBOS data on particle production at
midrapidity.Comment: 5 pages, 2 figure
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Limiting fragmentation from scale-invariant merging of fast partons
Exploiting the idea that the fast partons of an energetic projectile can be
treated as sources of color radiation interpreted as wee partons, it is shown
that the recently observed property of extended limiting fragmentation implies
a scaling law for the rapidity distribution of fast partons. This leads to a
picture of a self-similar process where, for fixed total rapidity Y, the
sources merge with probability varying as 1/y.Comment: 10 pages, 1 figure (2 eps files). Final version, also updated w.r.t.
the published version in Phys. Lett. B665/1 (2008) pp. 35-3
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
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