# Discovering the D0∗(2100) in B semileptonic decays

## TL;DR

This paper proposes a new method to detect a predicted subatomic particle, D0∗(2100), using specific decay processes in particle experiments.

## Contribution

The paper introduces angular asymmetries in B→Dπℓν decays to directly extract the Dπ S-wave phase shift and proposes a novel measurement strategy for the Belle II experiment.

## Key findings

- The Belle II experiment can determine the pole location of D0∗(2100) with sufficient precision using current data.
- The proposed method allows for measuring Dπ isospin 1/2 scattering length with accuracy to distinguish between theoretical predictions and experimental results.

## Abstract

The mass and width of the lightest scalar open-charm state listed in the Review of Particle Physics, the \documentclass[12pt]{minimal}
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\begin{document}$$D_0^*(2300)$$\end{document}D0∗(2300), are in puzzling tension with predictions from unitarized chiral perturbation theory (UChPT) and lattice QCD, which favor a lighter state at around 2100 MeV. However, to date, no direct experimental evidence for this lighter state exists. In an effort to facilitate a direct observation, we introduce angular asymmetries of \documentclass[12pt]{minimal}
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\begin{document}$$B\rightarrow D \pi \ell \nu $$\end{document}B→Dπℓν decays that allow for a direct extraction of the \documentclass[12pt]{minimal}
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\begin{document}$$D\pi $$\end{document}Dπ S-wave phase shift and discuss a novel measurement strategy for the Belle II experiment. We conduct a sensitivity study, finding that the Belle II experiment can determine the pole location with sufficient precision to firmly establish the \documentclass[12pt]{minimal}
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\begin{document}$$D_0^*(2100)$$\end{document}D0∗(2100) using the currently available data set. We also investigate the possibility and necessary statistics of measuring the \documentclass[12pt]{minimal}
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\begin{document}$$D\pi $$\end{document}Dπ isospin 1/2 scattering length with an accuracy sufficient to distinguish between the predictions from both UChPT and lattice QCD and the measurement by ALICE using femtoscopy.