A model-independent analysis of final-state interactions in \bar B_{d/s}^0 --> J/psi pi pi

TL;DR

This paper uses dispersion theory to analyze final-state interactions in B-meson decays to J/psi and pion pairs, providing a model-independent approach that improves understanding of strong interactions and CP violation.

Contribution

It introduces a dispersion-theory-based, model-independent analysis of B-meson decays to J/psi and pion pairs, accurately describing data and phases crucial for CP violation studies.

Findings

Excellent agreement with experimental data up to 1.05 GeV

Reduced number of parameters compared to phenomenological models

Correct phase structure for CP violation analysis

Abstract

Exploiting $B$-meson decays for Standard Model tests and beyond requires a precise understanding of the strong final-state interactions that can be provided model-independently by means of dispersion theory. This formalism allows one to deduce the universal pion-pion final-state interactions from the accurately known $\pi\pi$ phase shifts and, in the scalar sector, a coupled-channel treatment with the kaon-antikaon system. In this work an analysis of the decays $\bar B_d^0 \to J/\psi \pi^+\pi^-$ and $\bar B_s^0 \to J/\psi \pi^+\pi^-$ is presented. We find very good agreement with the data up to 1.05 GeV with a number of parameters reduced significantly compared to a phenomenological analysis. In addition, the phases of the amplitudes are correct by construction, a crucial feature when it comes to studies of $CP$ violation in heavy-meson decays.