The ATLAS experiment is commissioning its computing system in preparation for LHC data. Part of this activity consists in testing the data flow from the online data acquisition to the offline ...processing system, and the distribution of raw and processed data to the external computing centres. A series of functional and rate tests has been performed in 2006 and 2007, allowing the optimisation of the hardware and software components of this system; the last phase of commissioning, the so-called Final Dress Rehearsal, consisting of an integration tests of all components, will take place later in 2007. This paper describes the performed tests, the problems that we encountered, and the solutions we found.
Two-particle interferometry of positive kaons is studied in Pb+Pb collisions at mean transverse momenta <p(T)> approximately 0.25 and 0.91 GeV/c. A three-dimensional analysis was applied to the lower ...p(T) data, while a two-dimensional analysis was used for the higher p(T) data. We find that the source-size parameters are consistent with the m(T) scaling curve observed in pion-correlation measurements in the same collisions, and that the duration time of kaon emission is consistent with zero within the experimental sensitivity.
π−π−π− correlations from Pb+Pb collisions at 158 GeV/c per nucleon are presented as measured by the focusing spectrometer of the NA44 experiment at CERN. The three-body effect is found to be stronger ...for Pb+Pb than for S+Pb. The two-dimensional three-particle correlation function is also measured and the longitudinal extension of the source is larger than the transverse extension.
π
+
π
+
π
+ correlations from sulphur-lead collisions at 200 GeV/c per nucleon are presented as measured by the focusing spectrometer of experiment NA44 at CERN. We have investigated the three-pion ...correlation function at mid-rapidity and found that a genuine three-body correlation is suppressed. A possible interpretation of this result is that the emission of particles is partially coherent.
Proton distributions at midrapidity have been measured for 158A·GeV Pb+Pb collisions in the focusing spectrometer experiment NA44 at CERN. A high degree of nuclear stopping is found in the truly ...heavy ion collisions. Systematic results of single particle transverse momentum distributions of pions, kaons, and protons, of 200A·GeV S+S and 158A·GeV Pb+Pb central collisions will be addressed within the context of thermalization. By comparing these data with thermal and transport models, freeze-out parameters such as the temperature parameter
T
fo
and mean collective flow velocity 〈β〉 are extracted. Preliminary results of the particle ratios of
K
−
K
+
and
p
p
are discussed in the context of cascade models of RQMD and VENUS.
The NA44 Collaboration has measured yields and differential distributions of
K
+,
K
−,
π
+,
π
− in transverse kinetic energy and rapidity, around the center-of-mass rapidity in 158 A GeV/
c Pb+Pb ...collisions at the CERN SPS. A considerable enhancement of
K
+ production per
π is observed, as compared to
p+
p collisions at this energy. To illustrate the importance of secondary hadron rescattering as an enhancement mechanism, we compare strangeness production at the SPS and AGS with predictions of the transport model RQMD.
The use of the TWiki Web in ATLAS Amram, Nir; Antonelli, Stefano; Haywood, Stephen ...
Journal of physics. Conference series,
04/2010, Volume:
219, Issue:
8
Journal Article
Peer reviewed
Open access
The ATLAS Experiment, with over 2000 collaborators, needs efficient and effective means of communicating information. The Collaboration has been using the TWiki Web at CERN for over three years and ...now has more than 7000 web pages, some of which are protected. This number greatly exceeds the number of "static" HTML pages, and in the last year, there has been a significant migration to the TWiki. The TWiki is one example of the many different types of Wiki web which exist. In this paper, a description is given of the ATLAS TWiki at CERN. The tools used by the Collaboration to manage the TWiki are described and some of the problems encountered explained. A very useful development has been the creation of a set of Workbooks (Users' Guides) – these have benefitted from the TWiki environment and, in particular, a tool to extract pdf from the associated pages.
Correlations of two protons emitted near midrapidity in
p+
Pb collisions at 450 GeV/
c and
S+
Pb collisions at 200
A GeV/
c are presented, as measured by the NA44 Experiment. The correlation effect, ...which arises as a result of final state interactions and Fermi-Dirac statistics, is related to the space-time characteristics of proton emission. The measured source sizes are smaller than the size of the target lead nucleus but larger than the sizes of the projectiles. A dependence on the collision centrality is observed; the source size increases with decreasing impact parameter. Proton source sizes near midrapidity appear to be smaller than those of pions in the same interactions. Quantitative agreement with the results of RQMD (v1.08) simulations is found for
p+
Pb collisions. For
S+
Pb collisions the measured correlation effect is somewhat weaker than that predicted by the model simulations, implying either a larger source size or larger contribution of protons from long-lived particle decays.
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