Direct photons in p+p and A+A at RHIC
In this talk results on direct-photon production in p+p in A+A
collisions will be presented, including high-pT spectra and
gamma-hadron angular correlations. A highlight will be the new PHENIX
data on low-pT direct photons in p+p and Au+Au obtained with the
internal conversion method. This method exploits that any source of
real photons also emits virtual photons (i.e., e+e- pairs) with small
mass. The enhanced production of low-pT photons (1 < pT < 4 GeV/c) in
Au+Au provides evidence for the presence of thermal radiation as
expected from a quark-gluon plasma.