Erlangen 2026 – scientific programme

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T: Fachverband Teilchenphysik

T 69: Methods in Particle Physics IV

T 69.6: Talk

Thursday, March 19, 2026, 17:30–17:45, KH 00.020

Measurement of the η Reconstruction Efficiency at Belle II — •Johannes Mirfanger, Thomas Kuhr, and Thomas Lueck — Ludwig-Maximilians-Universität München (LMU), München, Germany

The precise reconstruction of η mesons is essential for a wide range of physics analyses at Belle II. This work presents a data-driven determination of the η reconstruction efficiency using the decay D^*+ → D⁰π⁺, comparing the two D⁰ decay modes D⁰→ K⁻π⁺ and D⁰→ K⁻π⁺η. By forming the ratio of these channels and correcting for the known branching fractions, we extract the η reconstruction efficiency of the Belle II detector. A key strength of this method is the ability to directly compare data and Monte Carlo simulation, enabling a clean assessment of potential discrepancies between them.

The extracted efficiency is further studied as a function of key kinematic variables, including the η momentum and polar angle. This offers detailed insight into detector performance across phase space. Ongoing work focuses on evaluating the robustness of the efficiency under varied event-selection criteria and on optimizing cut strategies for future analyses. The presentation will discuss the current status and give an outlook on the analysis.

Keywords: Eta mesons; Flavor Physics; Neutrals Reconstruction; Belle II