Ermes Aviano ; Diego Tonelli ; Benigno Gobbo ; Sebastiano Raiz

2024
Università degli Studi di Trieste Trieste

Abstract: This experimental particle-physics thesis explores a novel approach to the determination of the π0 meson reconstruction efficiency, whose uncertainty is a significant limitation in measurements sensitive to beyond Standard Model physics. I aim to determine the π0 reconstruction efficiency by comparing the rates of τ− → π− π^0 ντ with τ− → π− ντ decays recorded with the Belle II detector in SuperKEKB electron-positron collisions. Since these decays have large branching fractions known with high precision, have little background, and cover a wide range in π0 momentum, this approach would enable a reduction of the uncertainty on the π0 efficiency by up to a factor of three over current determinations. I develop the method starting from a simplified simulated sample comprising τ-pairs only and validate it against samples of known efficiency. Next, I extend the study to a fully realistic simulated sample, demonstrating the feasibility and performance of the method in realistic conditions. Finally, I briefly discuss various aspects of the applicability of the method to data. The results demonstrate that the π0 efficiency approach conceptually works and yields performances superior to existing Belle II methods.

Note: Presented on 18 10 2024
Note: MSc