Charged particles and photons have been measured in central Pb + Pb collisions at 158 A GeV in a common (eta-phi)-phase space region in the WA98 experiment at the CERN SPS. The measured distributions ...have been analyzed to quantify the frequency with which phase space regions of varying sizes have either small or large neutral pion fraction. The measured results are compared with VENUS model simulated events and with mixed events. Events with both large and small charged-neutral fluctuations are observed to occur more frequently than expected statistically, as deduced from mixed events, or as predicted by model simulations, with the difference becoming more prominent with decreasing size of the A Delta eta-Delta phi region. (C) 2011 Elsevier B.V. All rights reserved.
Neutral pion transverse momentum spectra were measured in p+C and p+Pb collisions at root s(NN) = 17.4 GeV at midrapidity (2.3 less than or similar to eta(lab)less than or similar to 3.0) over the ...range 0.7 less than or similar to p(T)less than or similar to 3.5 GeV/c. The spectra are compared to pi(0) spectra measured in Pb+Pb collisions at root s(NN) = 17.3 GeV in the same experiment. For a wide range of Pb+Pb centralities (N-part less than or similar to 300), the yield of pi(0)'s with p(T)greater than or similar to 2 GeV/c is larger than or consistent with the p+C or p+Pb yields scaled with the number of nucleon-nucleon collisions (N-coll), while for central Pb+Pb collisions with N-part greater than or similar to 350, the pi(0) yield is suppressed.
Measurements of direct photon production in p + Pb and p + C collisions at root(NN)-N-s = 17.4 GeV are presented. Upper limits on the direct photon yield as a function of p(T) are derived and ...compared to the results for Pb + Pb collisions at root(NN)-N-s = 17.3 GeV. The production of the eta meson, which is an important input to the direct photon signal extraction, has been determined in the eta -> 2 gamma channel for p + C collisions at root(NN)-N-s = 17.4 GeV. (c) 2012 Elsevier B.V. All rights reserved.
Two-particle correlations of direct photons were measured in central 208Pb+208Pb collisions at 158A GeV. The invariant interferometric radii were extracted for 100<K(T)<300 MeV/c and compared to ...radii extracted from charged pion correlations. The yield of soft direct photons, K(T)<300 MeV/c, was extracted from the correlation strength and compared to theoretical calculations.
Directed and elliptic flow of inclusive photons near mid-rapidity in 158
A GeV Pb
+
Pb collisions has been studied. The data have been obtained with the photon spectrometer LEDA of the WA98 ...experiment at the CERN SPS. The flow strength has been measured for various centralities as a function of
p
T
and rapidity over
0.18
<
p
T
<
1.5
GeV
/
c
and
2.3
<
y
<
2.9
. The angular anisotropy has been studied relative to an event plane obtained in the target fragmentation region that shows the elliptic flow to be in-plane. The elliptic flow has also been studied using two-particle correlations and shown to give similar results. A small directed flow component is observed. Both the directed and elliptic flow strengths increase with
p
T
. The photon flow results are used to estimate the corresponding neutral pion flow.
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.
Photon flow in 158 A GeV Pb+Pb collisions Nikolaev, Sergey; Aggarwal, M.M.; Angelis, A.L.S. ...
Nuclear Physics A,
2003, Letnik:
715
Journal Article, Conference Proceeding
Recenzirano
Directed and elliptic flow of π
0 - decay photons in 158 A GeV Pb+Pb collisions has been studied near midrapidity in an analysis of data obtained with the photon spectrometer LEDA of the WA98 ...experiment at the CERN SPS. Preliminary results on the rapidity and transverse momentum dependence of the flow have been obtained for various centralityclasses for
p
T
> 0.2GeV/c and 2.3 <
y < 2.9. The results are compared with the pion flow.
Particle density fluctuations Aggarwal, M.M.; Ahammed, Z.; Angelis, A.L.S. ...
Nuclear Physics A,
2003, Letnik:
715
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
Event-by-event fluctuations in the multiplicities of charged particles and photons at SPS energies are discussed. Fluctuations are studied by controlling the centrality of the reaction and rapidity ...acceptance of the detectors. Results are also presented on the event-by-event study of correlations between the multiplicity of charged particles and photons to search for DCC-like signals.
The mass, energy, and centrality dependence of rapidity density distributions of relativistic, charged particles, produced in heavy-ion interactions in the energy range 4A–200A GeV, are investigated. ...The results indicate that the rapidity density distributions show systematic variations, which are used to predict distributions for Au+Au and Pb+Pb interactions in a model-independent way.
PDF
