The azimuthal distributions of photons and charged particles with respect to the event plane are investigated as a function of centrality in Pb-208 + Pb-208 collisions at 158 (.) A GeV/c in the WA98 ...experiment at the CERN SPS. The anisotropy of the azimuthal distributions is characterized using a Fourier analysis. For both the photon and charged particle distributions the first two Fourier coefficients are observed to decrease with increasing centrality. The observed anisotropies of the photon distributions compare well with the expectations from the charged particle measurements for all centralities.
The Time Projection Chamber is the main tracking detector in the central barrel of the ALICE experiment. The task of large acceptance tracking in a heavy ion experiment is similar to that encountered ...in the NA49 and STAR experiments at the SPS and RHIC respectively. However, the extreme multiplicities of ion collisions at the LHC set qualitatively and quantitatively new demands making new designs indispensable. In this paper we present an overview of the main components, with special focus on the front-end and readout electronics, and some of the most crucial aspects addressed by the R&D activities that have preceded the design and construction of the ALICE TPC.
The ALICE dimuon spectrometer Baldisseri, A.
Nuclear Physics A,
2003, Letnik:
715
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
The Dimuon Spectrometer of the ALICE experiment is presented. The different subsystems are detailed with the final detector choices. Some important results of the R&D are shown. The physics ...performances are also reviewed.
A preshower photon multiplicity detector for the WA98 experiment Aggarwal, M.M.; Agnihotri, A.; Ahammed, Z. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/1999, Letnik:
424, Številka:
2
Journal Article
Recenzirano
Odprti dostop
A high granularity preshower detector has been fabricated and installed in the WA98 Experiment at the CERN SPS for measuring the spatial distribution of photons produced in the forward region in ...lead-ion-induced interactions. Photons are counted by detecting the preshower signal in plastic scintillator pads placed behind a 3 radiation length thick lead converter and applying a threshold on the scintillator signal to reject the minimum ionizing particles. Techniques to improve the imaging of the fibre and performance of the detector in the high multiplicity environment of lead–lead collisions are described. Using Monte-Carlo simulation methods and test beam data of π
− and e
− at various energies the photon counting efficiency is estimated to be 68% for central and 73% for peripheral Pb+Pb collisions.
Neutral pion production in central 158A GeV sup 208Pb+ sup 208 Pb collisions has been studied in the WA98 experiment at the CERN Super Proton Synchrotron. The pisup 0 transverse mass spectrum has ...been analyzed in terms of a thermal model with hydrodynamic expansion. The high accuracy and large kinematic coverage of the measurement allow one to limit previously noted ambiguities in the extracted freeze-out parameters. The results are shown to be sensitive to the shape of the velocity distribution at freeze-out. copyright ital 1999 ital The American Physical Society
Results on the study of localized fluctuations in the multiplicity of charged particles and photons produced in 158A GeV/c Pb+Pb collisions are presented for varying centralities. The charged versus ...neutral particle multiplicity correlations in common phase space regions of varying azimuthal sizes are analyzed by two different methods. Various types of mixed events are constructed to probe fluctuations arising from different sources. The measured results are compared to those from simulations and from mixed events. The comparison indicates the presence of nonstatistical fluctuations in both the charged particle and photon multiplicities in limited azimuthal regions. However, no correlated charged-neutral fluctuations, a possible signature of formation of disoriented chiral condensates, are observed. An upper limit on the production of disoriented chiral condensates is set.
The mean transverse momentum of photons has been determined on an event by event basis in S + Au collisions at 200 A·GeV from the ratio of the measured electromagnetic transverse energy (
E
T
em) to ...the photon multiplicity (
N
γ
). The average value obtained is similar to that determined for the same system using spectroscopic techniques. The centrality dependence of the measured values are in agreement with the predictions of the VENUS event generator.
4
Now at: SUBATECH, Ecole des Mines, Nantes, France.
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