The azimuthal distributions of photons and charged particles with respect to the event plane are investigated as a function of centrality in 208Pb + 208Pb 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 azimuthal distributions of photons and charged particles with respect to the event plane are investigated as a function of centrality in Pb + Pb 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 multiplicity of inclusive photons has been measured on an event-by-event basis for 158·
A GeV Pb induced reactions on Ni, Nb, and Pb targets. The systematics of the pseudorapidity densities at ...midrapidity (
ρ
max) and the width of the pseudorapidity distributions have been studied for varying centralities for these collisions. A power law fit to the photon yield as a function of the number of participating nucleons gives a value of 1.12±0.03 for the exponent. The mean transverse momentum, 〈
p
T
〉, of photons determined from the ratio of the measured electromagnetic transverse energy and photon multiplicity, remains almost constant with increasing
ρ
max. Results are compared with model predictions.
An event-by-event analysis of the azimuthal angular correlation with respect to the reaction plane has been carried out for
K
+ and
π
+ emission near mid-rapidity in 158
A·GeV Pb + Pb collisions. In ...semi-central collisions,
K
+ mesons are found to be preferentially emitted out of the reaction plane, while
π
+ mesons are emitted in the reaction plane. The results suggest that the kaon emission is influenced by in-medium potential effects in addition to collective flow effects.
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