Speaker
Description
PHENIX has measured low pT direct photon yields and elliptic flow in 200 GeV Au+Au collisions with three different methods and the results are consistent. The yield measurements have been extended to lower collision energies and different colliding systems. It has been found that the integrated yields scale with the respective charged particle density, independent of system size, collision energy or centrality, as long as the colliding systems are large, but the scaling breaks down for p+p. If this signals that a similar radiating medium is formed in all A+A collisions, but it is absent in p+p, it is a logical question whether there is a visible "turn-on" of medium formation. Using the p+Au and d+Au data collected by PHENIX we will report on the current status of these investigations.
