Measurement of the Luminosity in the ZEUS Experiment at HERA II

TL;DR

This paper reports on the upgraded methods and system for measuring luminosity in the ZEUS experiment at HERA II, achieving a systematic uncertainty of 1.7% through redundant techniques.

Contribution

The paper introduces a modified luminosity-measuring system with radiation-hard components and an independent magnetic spectrometer for improved accuracy.

Findings

Achieved a systematic uncertainty of 1.7% in luminosity measurement.

Implemented radiation-hard scintillator tiles and shielding for higher photon rates.

Established a reliable, redundant luminosity determination method.

Abstract

The luminosity in the ZEUS detector was measured using photons from electron bremsstrahlung. In 2001 the HERA collider was upgraded for operation at higher luminosity. At the same time the luminosity-measuring system of the ZEUS experiment was modified to tackle the expected higher photon rate and synchrotron radiation. The existing lead-scintillator calorimeter was equipped with radiation hard scintillator tiles and shielded against synchrotron radiation. In addition, a magnetic spectrometer was installed to measure the luminosity independently using photons converted in the beam-pipe exit window. The redundancy provided a reliable and robust luminosity determination with a systematic uncertainty of 1.7%. The experimental setup, the techniques used for luminosity determination and the estimate of the systematic uncertainty are reported.