3 research outputs found
Direct Photon Production in 158 AGeV Pb+Pb Collisions
A measurement of direct photon production in Pb+Pb collisions at 158 AGeV has
been carried out in the CERN WA98 experiment. The invariant yield of direct
photons in central collisions is extracted as a function of transverse momentum
in the interval 0.5 < pT < 4 GeV/c. A significant direct photon signal,
compared to statistical and systematical errors, is seen at pT > 1.5 GeV/c. The
results constitute the first observation of direct photons in ultrarelativistic
heavy-ion collisions which could be significant for diagnosis of quark gluon
plasma formation.Comment: Talk presented at Nucleus-Nucleus 2000, Strasbourg, Franc
Azimuthal Anisotropy of Photon and Charged Particle Emission in Pb+Pb Collisions at 158 A GeV/c
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