A study of elliptic flow and two-particle azimuthal correlations of charged particles (\(0.5 < p_{{\text{T}}} < 2.5\) GeV/c) and high-\(p_{\rm T}\) pions (\(1.2 < p_{{\text{T}}} < 3.5\) GeV/c) in Pb ...+ Au collisions at 158A GeV/c, close to midrapidity, is presented. Elliptic flow (v2) rises linearly with \(p_{\rm T}\) to a value of about 10\(\%\) at 2 GeV/c. Beyond \(p_{\rm T}\approx\) 1.5 GeV/c, the slope decreases and possibly indicates a v2 saturation at high \(p_{\rm T}\). Two-pion azimuthal anisotropies for \(p_{\rm T} > \) 1.2 GeV/c exceed the v2 values by about 60\(\%\) in semicentral collisions. This non-flow component is attributed to near-side and away-side jetlike correlations. While the near-side peak remains constant with centrality 0.23\(\pm\)0.03 rad, as expected for fragmentation, the away-side peak experiences broadening and disappears in central collisions.
Cherenkov ring fitting techniques for the CERES RICH detectors Agakichiev, G; Drees, A; Glässel, P ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/1996, Letnik:
371, Številka:
1
Journal Article
Recenzirano
The CERES experiment studies the production of low-mass electron pairs in proton-proton, proton-nucleus and nucleus-nucleus collisions at the CERN-SPS. Particle identification and momentum ...measurement are solely based on two azimuthally symmetric RICH detectors. The off-line reconstruction of electron rings has to be preformed without prior knowledge of the cherenkov ring centers, a demand which is unique as compared to other RICH applications using the rings for particle identification or rejection only. During the last years the CERES collaboration has developed several algorithms to cope with the problems of ring recognition in a background-contaminated environment. Here we report on encouraging experiences with the
robust ring fitting technique based on a reweighted least-squares method and compare its performance with previously used algorithms based on the minimization of summed Gaussian weights.
Measurements of event-by-event fluctuations of the mean transverse momentum in PbAu collisions at 40, 80, and 158
A
GeV/c
are presented. A significant excess of mean
p
T
fluctuations at ...mid-rapidity is observed over the expectation from statistically independent particle emission. The results are somewhat smaller than recent measurements at RHIC. A possible non-monotonic behavior of the mean
p
T
fluctuations as function of collision energy, which may have indicated that the system has passed the critical point of the QCD phase diagram in the range of
μ
B
under investigation, has not been observed. The centrality dependence of mean
p
T
fluctuations in PbAu is consistent with an extrapolation from
pp collisions assuming that the non-statistical fluctuations scale with multiplicity. The results are compared to calculations by the
rqmd and
urqmd event generators.
We report on the performance of a doublet of 3 in. cylindrical silicon drift detectors installed as an upgrade of the CERES/NA45 electron pair spectrometer for the Pb-beam at the CERN SPS. The ...silicon detectors provide external particle tracking and background rejection of conversions and close Dalitz pairs. Results on vertex reconstruction and rejection from a Pb test-run in 1994 are presented.
In a joint effort the CERES/NA45 and TAPS collaborations have measured low-mass electron pairs in p–Be and p–Au collisions at 450 GeV/ at the CERN SPS. In the range covered up to 1.5 GeV/ the mass ...spectra from p–Be and p–Au collisions are well explained by electron pairs from decays of neutral mesons. For p–Au our result is new. For p–Be, the simultaneously measured electron pair inclusive pair spectrum in which instrumental uncertainties are highly reduced. We confirm the earlier finding of HELIOS-1 with significantly reduced systematic uncertainties of 23% in the mass range below 450 MeV/, and of 28% in the mass range above 750 MeV/ at 90% confidence limit. Any unconventional source of electron pairs is limited by these error margins as the percentage fraction of the hadronic contribution.
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