## Measurement of photons via conversion pairs in \sqrt{s_{NN}} = 200 GeV Au + Au with the PHENIX experiment at RHIC

### Torsten Dahms

Thermal photons can provide information on the temperature of a possible QGP produced at RHIC. In the p_{T} region of 1-3 GeV/c thermal photons are expected to be the dominant direct photon source. Therefore, a possible excess compared to a pure decay photon signal due to a thermal photon contribution would be seen in the double ratio (\gamma/\gamma(\pi^{0}))measured/(\gamma/ \gamma(\pi^{0}))simulated.

We present a new method to reconstruct direct photons by measuring e^{+}e^{-}-pairs from external photon conversions. Tracks are reconstructed in PHENIX under the assumption that they originate from the collision vertex. This effectively leads to a momentum misreconstruction for tracks that do not originate from that point. As a result the conversion pairs acquire an apparent mass and a characteristic orientation relative to the magnetic field direction. These properties can be used to distinguish the background of e^{+}e^{-}-pairs from the \pi^{0} Dalitz decay from external conversion pairs. The background of photons from \pi^{0} decays is measured by reconstructing the \pi^{0} invariant mass of \gamma e^{+} e^{-}-triplets. A direct photon signal could be extracted from the remaining e+e- pairs from external conversions.