Bottomonium Spectrum with Coupled-Channel Effects

TL;DR

This paper investigates the bottomonium spectrum using a nonrelativistic quark model with coupled-channel effects, revealing significant mass shifts and suggesting certain states as exotic beyond traditional quark models.

Contribution

It introduces a detailed analysis of coupled-channel effects on bottomonium, providing updated mass predictions and insights into potential exotic states like $Y_b(10890)$.

Findings

Large mass shifts due to coupled-channel effects

Identification of $Y_b(10890)$ as a possible exotic state

Predicted $ ext{chi}_b(3P)$ masses align with experimental data

Abstract

We study the bottomonium spectrum in the nonrelativistic quark model with the coupled-channel effects. The mass shifts and valence $b\bar{b}$ component are evaluated to be rather large. We find that the hadronic loop effects can be partially absorbed into a reselection of the model parameters. No bottomonium state except $\Upsilon(5\,^1S_0)$ and $\Upsilon(5\,^3S_1)$ with mass around 10890 MeV is found in the quark models both with and without coupled-channel effects, so we suggest that $Y_{b}(10890)$ is an exotic state beyond the quark model, if it is confirmed to be a new resonance. The predictions for the $\chi_b(3P)$ masses are consistent with the ATLAS measurements. If some new bottomonium-like states are observed at LHCb or SuperB in the future, we can determine whether they are conventional bottomonium or exotic states by comparing their masses with the mass spectrum predicted in our work.