Erlangen 2026 – wissenschaftliches Programm

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HK: Fachverband Physik der Hadronen und Kerne

HK 3: Hadron Structure and Spectroscopy II

HK 3.6: Vortrag

Montag, 16. März 2026, 17:45–18:00, PHIL A 401

Background Modelling in Partial-Wave Analysis of τ⁻ → π⁺ π⁻π⁻ ν_τ decays at Belle II — •Miriam Weiskopf, Godo Kurten, Hans-Günther Moser, Stephan Paul, Claudia Perez-Orive, and Stefan Wallner — Max Planck Institut for Physics, Boltzmannstraße 8, Garching 85748, Germany

We study light mesons appearing as intermediate resonances in the τ⁻ → π⁺ π⁻π⁻ ν_τ decays at the Belle II experiment where τ pairs are produced in e⁺e⁻ collisions. A detailed partial wave-analysis is performed to identify resonances that appear in the 3π system and to measure their properties including spin, parity, mass and width.

We will present our neural-network based approach that is used to model the distributions of backgrounds, such as τ⁻ → π⁺ π⁻π⁻ π₀ ν_τ or e⁺e⁻ → q q, in our data sample. We address challenges such as the high dimensionality of the phase space, limited data coverage, sharp background features, and background distributions that vary across different kinematic regions. The modelled background distributions and their integration into the partial-wave analysis will be presented.

Keywords: Partial-Wave Analysis; Belle/Belle II; Background Modeling; Meson Spectroscopy; Machine Learning