Abstract: The Belle II experiment at the SuperKEKB collider provides a rich programme of flavor physics measurements, offering opportunities to test the Standard Model and search for indirect signs of physics beyond it. Rare and suppressed B-meson decays are particularly interesting in this context, as they provide sensitivity to fundamental parameters and hadronic effects that are difficult to access through other processes. This seminar will introduce the physics opportunities offered by Belle II, with a particular focus on the radiative leptonic decay B⁺ → ℓ⁺ ν_ℓ γ, which provides access to the internal structure of the B meson through its light-cone distribution amplitude and the poorly constrained inverse moment λ_B.
The analysis exploits the recoil-mass technique, which enables the identification of signal decays by reconstructing the accompanying B meson in the event. A key challenge is achieving sufficient efficiency and purity in this reconstruction while retaining sensitivity to the signal-side kinematics. The seminar will discuss the analysis strategy and the development of new B-tagging techniques aimed at improving reconstruction efficiency and background suppression, with the broader goal of enabling precise recoil-based measurements at Belle II. The seminar will also provide an introduction to the underlying concepts and experimental techniques, making it suitable for PhD students and anyone curious about flavour physics and B-tagging.