Production of loosely-bound hadron molecules from bottomonium decays

TL;DR

This paper investigates the production of loosely-bound hadron molecules in bottomonium decays and $e^+e^-$ collisions, testing models against data, predicting spectra and production rates, and refining Monte Carlo simulations for future experiments.

Contribution

It provides the first comprehensive comparison of deuteron production models with data and predicts yields of exotic states like the H dibaryon and hypertriton at Belle II energies.

Findings

Models can reproduce existing deuteron production data within uncertainties.

Predicted deuteron spectra differ but are compatible with current data.

Predictions for H dibaryon production are below current limits but accessible to Belle II.

Abstract

We present multiple results on the production of loosely-bound molecules in bottomonium annihilations and $e^+e^-$ collisions at $\sqrt{s} = 10.58$ GeV. We perform the first comprehensive test of several models for deuteron production against all the existing data in this energy region. We fit the free parameters of the models to reproduce the observed cross sections, and we predict the deuteron spectrum and production and the cross section for the $e^+e^- \to d\bar{d} + X$ process both at the $\Upsilon(1,2,3S)$ resonances and at $\sqrt{s}=10.58$ GeV. The predicted spectra show differences but are all compatible with the uncertainties of the existing data. These differences could be addressed if larger datasets are collected by the Belle~II experiment. Fixing the source size parameter to reproduce the deuteron data, we then predict the production rates for $H$ dibaryon and hypertriton in this energy region using a simple coalescence model. Our prediction on $H$ dibaryon production rate is below the limits set by the direct search at the Belle experiment, but in the range accessible to the Belle~II experiment. The systematic effect due to the MC modelling of quarks and gluon fragmentation into baryons is reduced deriving a new tuning of the \pythia MonteCarlo generator using the available measurement of single- and double-particle spectra in $\Upsilon$ decays.