• Physics
• axions
• ALPs
• SVD
• Belle2
• BelleII
• Hit time reconstruction

The goal of this thesis is the search for an Axion-Like Particle (ALP) A in the decay B±→K±A, A→γγ in the data collected by the BABAR experiment, and the projections to the Belle II experiment.
I reconstructed the decay of a charged B meson into a charged K and two photons, and searched resonances in the diphoton invariant mass spectrum. Various multivariate analysis have been tested to discriminate the signal from the two main backgrounds, i.e. the one related to B decays and the one related to light quarks production (uds) and quark c.
The signal yield is extracted from a fit to the diphoton invariant mass distribution.
The efficiency of the selection is between 17% and 19% for the signal, while the efficiency for the background events of type B and uds is, respectively, 5.0 × 10−6 and 3.9 × 10−6.
I also contributed to the Belle II Silicon Vertex Detector reconstruction software, developing and implementing the algorithm to extract the hit time of the particles crossing the detector. Using this time information it is possible to reduce the off-time background and therefore significantly improve the tracking performances.