Mainz 2022 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 39: Computing II

HK 39.4: Talk

Wednesday, March 30, 2022, 14:45–15:00, HK-H5

Reconstruction of Photon Conversions with the ALICE Transition Radiation Detector — •Martin Kroesen for the ALICE collaboration — Physikalisches Institut, Universität Heidelberg

So called direct photons give us an undisturbed insight to the Quark Gluon Plasma created in relativistic heavy ion collisions. A huge statistics is needed for this analysis since the background is large and the reconstruction efficiency via the Photon Conversion Method (PCM) relatively low. Therefore the ALICE Transition Radiation Detector (TRD), which is located at a radius of about 3 m, is now employed for photon reconstruction using the PCM. It is shown that it is possible to reconstruct these photons with the TRD information only. This enables an increase of the total photon efficiency in ALICE as well as a cross check additional to the standard reconstruction of photon conversions in the Time Projection Chamber. For that purpose a full stand alone tracking algorithm using a combinatorial search was developed. Based on TensorFlow a high precision photon hypothesis test and parameter fit completes the reconstruction by exploiting topological constraints. The stand alone TRD tracks can also be used for other purposes such as calibration or nuclear interaction analyses. First results from the p-Pb run in 2018 are presented, showing a peak for π⁰ → γ γ → e⁺ e⁻ e⁺ e⁻.