Study of BESIII electromagnetic calorimeter performance with radiative lepton pair events

TL;DR

This paper evaluates the performance of the BESIII electromagnetic calorimeter by analyzing photon detection efficiency and spatial resolution using radiative lepton pair events at specific resonances.

Contribution

It introduces a calibration method for photon detection efficiency and studies the spatial resolution of the EMC using control samples from ISR processes.

Findings

Photon detection efficiency measured using kinematic fits.

Spatial resolution characterized in polar and azimuthal angles.

Calibration techniques improve EMC performance understanding.

Abstract

We study the photon detection efficiency and position resolution of the electromagnetic calorimeter (EMC) of the BESIII detector. The control samples of the initial-state-radiation (ISR) process of $e^+e^-\rightarrow \gamma \mu^+\mu^-$ at $J/\psi$ and $\psi(3770)$ resonances are used for the calibration of the photon cluster shapes and photon detection efficiency study. The photon detection efficiency is defined as the fraction of predicted photon, determined by performing a kinematic fit with the four momenta of two charged tracks only, matched with the actual photons in the EMC. The spatial resolution of the EMC is studied in polar ($\theta$) and azimuthal ($\phi$) angle directions in a cylindrical coordinate system centered at the interaction point, with z-axis along the beam direction.