Studies of the tracking and identification efficiencies of electrons and positrons at BESIII

TL;DR

This work quantifies electron tracking and PID efficiencies at BESIII using radiative Bhabha events at $\sqrt{s}=3.08$ and $3.097$ GeV, defines robust data/MC correction factors, and characterizes systematic uncertainties. Through tag-and-probe analyses, the study obtains $\epsilon$ and $\alpha$ for both data and MC, finding that after correction the relative differences are typically below $0.5\%$, with especially small residuals in most $p_T$ and $p$ bins. The results include detailed $p_T$ and $\cos\theta$ (tracking) and $p$, $\cos\theta$ (PID) dependences, and provide correction-factor tables to improve MC modeling for electron-related analyses. These corrections and methodologies enable more precise physics measurements at BESIII by reducing electron-related systematic uncertainties and are broadly applicable to other processes analyzed with BESIII data.

Abstract

The efficiencies for electron and positron tracking and identification in the BESIII experiment are investigated with the radiative Bhabha process $e^+e^-\rightarrow e^+e^-γ$ from the data samples collected at the center-of-mass energies of 3.08 GeV and 3.097 GeV. The relative differences between data and MC associated with tracking and identification efficiencies of electrons and positrons, as well as the corresponding correction factors are determined. It turns out the relative differences of tracking efficiency and particle identification efficiency after correction are mostly less than 0.5$\%$ for transverse momenta $p_T>0.4$ GeV and for the entire momentum region, respectively.

Figures (8)

• Figure 1: Distributions of the isolation angle (left) and $\chi^2$ (right) for selected data and MC samples in the tracking efficiency study.
• Figure 2: Distributions of transverse momentum (left), momentum (middle) and $\cos\theta$ (right) for the probed electrons in the tracking efficiency study.
• Figure 3: Electron (left) and positron (right) tracking efficiencies of data (top) and MC (middle) as well as the correction factor (bottom) versus $p_T$ and $\cos\theta$.
• Figure 4: Relative difference in the electron (top row) and positron (bottom row) tracking efficiencies between data and MC (left) and the uncertainty of the correction factor (right) versus $p_{T}$ and $\cos\theta$.
• Figure 5: Distribution of the total energy deposited in the EMC for selected data and MC samples in PID efficiency study.