# Generating a resonance-like structure in the reaction $B_c\to B_s \pi\pi$

## TL;DR

This paper predicts a resonance-like structure in the decay $B_c^+ o B_s^0 \pi^+\pi^0$ caused by triangle singularities, suggesting it is a kinematic effect rather than a new particle, which could impact interpretations of exotic states.

## Contribution

It demonstrates that a resonance-like feature in $B_s^0 \pi^+$ invariant mass arises from triangle singularities, providing a non-resonant explanation for certain observed structures.

## Key findings

- A resonance-like structure $X(5777)$ is predicted near the $Bar{K}$ threshold.
- The structure is explained as a kinematic effect, not a genuine resonance.
- Observation of this effect could influence interpretations of $XYZ$ particles.

## Abstract

We investigate the process $B_c^+\to B_s^0\pi^+\pi^0$ via $B\bar{K}^*$ rescattering. The kinematic conditions for triangle singularities are perfectly satisfied in the rescattering diagrams. A resonance-like structure around the $B\bar{K}$ threshold, which we denote as $X(5777)$, is predicted to be present in the invariant mass distribution of $B_s^0 \pi^+$. Because the relative weak $B\bar{K}$ $(I=1)$ interaction does not support the existence of a dynamically generated hadronic molecule, the $X(5777)$ can be identified as a pure kinematical effect due to the triangle singularity. Its observation may help to establish a non-resonance interpretation for some $XYZ$ particles.