Accessing the ALPs : Reconstructing merged two-photon decays in the Belle II detector Whiteaker, Kelton
Axion-like particles (ALPs) are spin 0 bosons proposed to mediate interactions between dark matter and the Standard Model. The Belle II detector at the SuperKEKB e+e− accelerator in Japan is well-suited to search for an ALP to twophoton decay; however, a large fraction of possible two-photon ALP decays, and a large fraction of Standard Model two-photon decays, remain unresolvable in the detector due to the small opening angle between their daughter photons. This small opening angle makes the Belle II photon detector software interpret the pair of photons as a single photon: this is called a merge. This project will explore various methods of classification, including a machine learning algorithm, to enable Belle II users to manually distinguish between a single photon and two merged photons. The machine learning algorithm presented is able to distinguish the two cases to a high degree of accuracy, but even without its implementation, tools already available at Belle II that can help with this problem are identified.
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