Measurement of the integrated luminosity of the Phase 2 data of the Belle II experiment

TL;DR

This paper reports the first measurement of the integrated luminosity for the initial Belle II data sample collected at the SuperKEKB collider, establishing a foundation for future analyses.

Contribution

It introduces the first luminosity measurement for Belle II using Bhabha and digamma events, with detailed uncertainty analysis.

Findings

Measured integrated luminosity: 496.3 pb$^{-1}$

Uncertainty: ±0.3 (stat) ±3.0 (syst) pb$^{-1}$

Provides a baseline for future luminosity measurements

Abstract

From April to July 2018, a data sample at the peak energy of the $\Upsilon(4S)$ resonance was collected with the Belle~II detector at the SuperKEKB electron-positron collider. This is the first data sample of the Belle~II experiment. Using Bhabha and digamma events, we measure the integrated luminosity of the data sample to be ($496.3 \pm 0.3 \pm 3.0$)~pb$^{-1}$, where the first uncertainty is statistical and the second is systematic. This work provides a basis for future luminosity measurements at Belle~II.