474 research outputs found
Multiparticle correlations from momentum conservation
Using a generating-function formalism, we compute the contribution of
momentum conservation to multiparticle correlations between the emitted
particles in high-energy collisions. In particular, we derive a compact
expression of the genuine M-particle correlation, for arbitrary M.Comment: 5 pages, RevTeX. v2: typos corrected, to match journal versio
Directed flow at RHIC from Lee-Yang zeroes
Directed flow in ultrarelativistic nucleus-nucleus collisions is analyzed
using the reaction plane from elliptic flow, which reduces the bias from
nonflow effects. We combine this method with the determination of elliptic flow
from Lee-Yang zeroes. The resulting method is more consistent and somewhat
easier to implement than the previously used method based on three-particle
cumulants, and is also less biased by nonflow correlations. Error terms from
residual nonflow correlations are carefully estimated, as well as statistical
errors. We discuss the application of the method at RHIC and LHC.Comment: 10 pages. Final version, to appear in Nucl. Phys.
Phase space constraints and statistical jet studies in heavy-ion collisions
The effect of the correlation induced by global momentum conservation on the
two-particle distribution in nucleus-nucleus collisions is discussed, with a
focus on the generic case of collisions with a non-vanishing impact parameter.Comment: 5 pages, invited talk at the RHIC & AGS Annual Users' Meeting,
Brookhaven Nat. Lab. (USA) and at the EPS HEP 2007 Conference, Manchester
(UK
Hints of incomplete thermalization in RHIC data
The large elliptic flow observed in Au-Au collisions at RHIC is often put
forward as a compelling evidence for the formation of a strongly-interacting
quark-gluon plasma. The main argument is that the measured elliptic flow is as
large as the value given by fluid-dynamics models that assume complete
thermalization. It is argued that this claim may not be justified, since a
detailed examination of experimental data rather suggests that the system
created is not fully equilibrated at the time when anisotropic flow develops.Comment: 8 pages, 2 eps-figures, Talk given at the Workshop on QGP
Thermalization (QGPTH05), Vienna, 10-12 Aug 200
Momentum conservation and correlation analyses in heavy-ion collisions at ultrarelativistic energies
Global transverse-momentum conservation induces correlations between any
number of particles, which contribute in particular to the two- and
three-particle correlations measured in heavy-ion collisions. These
correlations are examined in detail, and their importance for studies of jets
and their interaction with the medium is discussed.Comment: 5 pages, 2 figures. v2: corrected typos and added a paragrap
Directed and Elliptic Flow in Pb+Pb collisions at 40 and 158 AGeV
Directed and elliptic flow are reported for charged pions and protons as a
function of transverse momentum, rapidity, and centrality in 40 and 158 AGeV Pb
+ Pb collisions. The standard method of correlating particles with an event
plane is used. The directed flow of protons is small and shows little variation
near to midrapidity, but rises fast towards projectile rapidity in the 40 AGeV
data. For most peripheral collisions the flat region becomes negative resulting
in changing sign three times. Elliptic flow doesn't seem to change very
much from 40 AGeV to 158 AGeV. The difference is smaller than anticipated from
the overall energy dependence from AGS to RHIC.Comment: Presented at 16th International Conference on Ultrarelativistic
Nucleus-Nucelus Collisions, Quark Matter 2002 (QM 2002), Nantes, France,
18-24 Jul 2002, 4 pages, 3 figure
Genuine collective flow from Lee-Yang zeroes
We propose to use the theory of phase transitions of Lee and Yang as a
practical tool to analyze long-range correlations in a finite-size system. We
apply it to the analysis of anisotropic flow in nucleus-nucleus collisions, and
show that this method is more reliable than any other used so far.Comment: 5 pages, 3 eps figures, RevTeX. v2: overall presentation modifie
Are there monojets in high-energy proton-nucleus collisions?
We study high-energy proton-nucleus collisions within the Colour Glass
Condensate framework, and compute the probabilities of having a definite number
of scatterings in the nucleus with a momentum transfer larger than a given cut.
Various properties of the distribution in the number of multiple scatterings
are investigated, and we conclude that events with monojets are very unlikely,
except for extreme values of the saturation scale Qs.Comment: 4 pages, 4 eps-figures. Talk given at Quark Matter 2006, Shanghai,
14-20 Nov. 200
Analysis of directed flow from three-particle correlations
We present a new method for analysing directed flow, based on a
three-particle azimuthal correlation. It is less biased by nonflow correlations
than two-particle methods, and requires less statistics than four-particle
methods. It is illustrated on NA49 data.Comment: Contribution to Quark Matter 2002, Nantes, July 18-24, 200
Elliptic flow in proton-proton collisions at 7 TeV
The angular correlations measured in proton-proton collisions at 7 TeV are
decomposed into contributions from back to back emission and elliptic flow.
Modeling the dominant term in the correlation functions as a momentum
conservation effect or as an effect of the initial transverse velocity of the
source, the remaining elliptic flow component can be estimated. The elliptic
flow coefficient extracted from the CMS Collaboration data is 0.04-0.08. No
additional small-angle, ridge-like correlations are needed to explain the
experimental data
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