Measurement of the electron reconstruction efficiency at LHCb

TL;DR

This paper measures the electron reconstruction efficiency at LHCb using B+ decay data, providing correction factors that improve the accuracy of electron-related measurements with less than 1% systematic uncertainty.

Contribution

It introduces a novel method to calibrate electron reconstruction efficiency using partially reconstructed decays, enhancing measurement precision at LHCb.

Findings

Agreement between data and simulation evaluated

Correction factors derived for simulated electrons

Systematic uncertainty below 1% for electron measurements

Abstract

The single electron track-reconstruction efficiency is calibrated using a sample corresponding to $1.3~\mathrm{fb}^{-1}$of $pp$ collision data recorded with the LHCb detector in 2017. This measurement exploits $B^+\to J/\psi (e^+e^-)K^+$ decays, where one of the electrons is fully reconstructed and paired with the kaon, while the other electron is reconstructed using only the information of the vertex detector. Despite this partial reconstruction, kinematic and geometric constraints allow the $B^+$-meson mass to be reconstructed and the signal to be well separated from backgrounds. This in turn allows the electron reconstruction efficiency to be measured by matching the partial track segment found in the vertex detector to tracks found by LHCb's regular reconstruction algorithms. The agreement between data and simulation is evaluated, and corrections are derived for simulated electrons in bins of kinematics. These correction factors allow LHCb to measure branching fractions involving single electrons with a systematic uncertainty below $1\%$.