The QED contribution to $J/\psi$ plus light hadrons production at B-factories

TL;DR

This paper investigates the production mechanisms of $J/ar{J}$ plus light hadrons at B-factories, highlighting the significant QED contribution and proposing methods to isolate the QCD component through angular cuts and distribution analysis.

Contribution

It provides a detailed analysis of QED contributions to $J/ar{J}$ plus light hadrons production and suggests strategies to extract the QCD signal by reducing QED background effects.

Findings

QED contribution is dominant across the phase space without cuts.

Angular cuts can significantly reduce QED background, making QCD contributions comparable.

Calculated angular and momentum distributions aid in separating QED and QCD processes.

Abstract

To understand the direct $J/\psi+X_{\mathrm{non-c\bar{c}}}$ production mechanism in $e^{+}e^{-}$ annihilation, in this work, we propose to measure the inclusive $J/\psi$ plus light hadrons (LH) production at B-factories and present a detailed study on its QED production due to $\psi(2S)$ feed-down, where the $\psi(2S)$ are produced in $e^{+}e^{-}\to \psi(2S)+\gamma$ and $e^{+}e^{-}\to \psi(2S)+f\bar{f}, f=lepton,light quark$, and QED contribution to direct $J/\psi+q\bar{q}$ production with $q=u,d,s$ quark. We find that the QED contribution is huge in the whole phase space region, but can be reduced largely and is in the same order as the QCD contribution when a suitable cut on the angel $\theta_{J/\psi}$ between $J/\psi$ and the $e^{+}e^{-}$ beam is made. In this way, the cross section of $J/\psi+LH$ QCD production %which was predicted theoretical at next-to-leading order QCD together with relativistic correction, can be obtained by subtracting the QED contribution from the experimental measurement on inclusive $J/\psi$ plus light hadrons. To help to remove the QED background, we also calculate the angular and momentum distribution of $J/\psi$ in the QED contribution.