Inclusive charged and neutral particle multiplicity distributions in $\chi_{cJ}$ and $J/\psi$ decays

TL;DR

This study measures inclusive charged and neutral particle multiplicity distributions in $\\chi_{cJ}$ and $J/\psi$ decays using BESIII data, compares results with Monte Carlo simulations, and highlights the importance of G-parity conservation.

Contribution

It provides detailed measurements of particle multiplicity distributions in charmonium decays and introduces a method to connect detected and produced distributions using Monte Carlo matrices.

Findings

Charged particle multiplicities agree with previous results from MARK I.

Photon distribution analysis suggests G-parity conservation impacts simulations.

Monte Carlo matrices effectively relate detected and produced distributions.

Abstract

Using a sample of 106 million $\psi(3686)$ decays, $\psi(3686) \to \gamma \chi_{cJ} (J = 0, 1, 2)$ and $\psi(3686) \to \gamma \chi_{cJ}, \chi_{cJ} \to \gamma J/\psi$ $(J = 1, 2)$ events are utilized to study inclusive $\chi_{cJ} \to$ anything, $\chi_{cJ} \to$ hadrons, and $J/\psi \to$ anything distributions, including distributions of the number of charged tracks, electromagnetic calorimeter showers, and $\pi^0$s, and to compare them with distributions obtained from the BESIII Monte Carlo simulation. Information from each Monte Carlo simulated decay event is used to construct matrices connecting the detected distributions to the input predetection "produced" distributions. Assuming these matrices also apply to data, they are used to predict the analogous produced distributions of the decay events. Using these, the charged particle multiplicities are compared with results from MARK I. Further, comparison of the distributions of the number of photons in data with those in Monte Carlo simulation indicates that G-parity conservation should be taken into consideration in the simulation.