On minimum-bias effects at the LHC

TL;DR

This paper evaluates the effectiveness of minimum-bias triggers at the LHC, showing they miss a significant portion of events and emphasizing the importance of accurate models for total cross section measurements.

Contribution

It provides quantitative estimates of signal rejection rates using the Durham model and highlights the necessity of reliable models for inelastic cross section determination.

Findings

Expected signal is about half of the total cross section.

Zero-bias measurement cross section is calculated for CMS.

Models must accurately predict minimum-bias cross sections to determine total inelastic cross section.

Abstract

In general, minimum-bias triggers planned for experiments at the LHC miss a considerable fraction of the total number of events. We exemplify the rejection rate using the Durham model of soft high-energy interactions to obtain quantitative estimates of the signals arising from the ATLAS scintillation counters positioned in the rapidity intervals 2<|eta|<4, and also from TOTEM detectors covering the intervals 3.1<|eta|<6.5. Typically we find that the expected signal is about half of the total cross section, sigma(tot). We also calculate the cross section for the so-called zero-bias measurement planned by CMS in the extended rapidity interval -5<eta<7. We emphasize that only models which give satisfactory predictions for the measured minimum-bias or zero-bias cross sections can be used to obtain the value of the total inelastic cross section.