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Abstract

The soft-photon puzzle has been an open problem in high energy particle physics for many years now. Experiments have been performed in the past to try to measure the soft-photon spectrum of inelastic m → n scattering processes. Some measured an excess of a factor 4–8 in terms of the internal bremsstrahlung spectrum predicted by Low’s theorem, but others measured no excess at all. This work presents for the first time a full Monte Carlo simulation with generated internal bremsstrahlung photons predicted by Low’s theorem propagated through the detector setup of ALICE 3. One of the goals of the proposed ALICE 3 experiment is to measure the soft-photon spectrum with the use of the Forward Conversion Tracker through the tracking of e+e− conversion pairs in a separate dipole magnetic field. Through dedicated studies of the (spatial) origin of the various sources of background, cuts and vetoes are implemented to minimize its impact on the measurement. These studies show a significance of 5–10 in the regime of 0.5 < kT < 7.5 MeV/c for the case where the excess is 4 times the predicted internal bremsstrahlung spectrum. A conical modification of the beam pipe is suggested to reduce the material budget in front of the FCT and as such the kinematic regime where the significance exceeds 5 is extended to 0.5 < kT < 10 MeV/c for the case where the excess is 4 times the predicted internal bremsstrahlung spectrum. In this thesis the theory, previous measurements and the performance of the proposed Forward Conversion Tracker will be discussed.