# The active muon shield in the SHiP experiment

## TL;DR

The paper presents the design, optimization, and performance evaluation of an active muon shield crucial for reducing muon background in the SHiP experiment, enabling the search for weakly interacting particles.

## Contribution

It introduces a novel active muon shield concept and details its optimization process and effectiveness in background suppression for the SHiP experiment.

## Key findings

- The muon shield effectively reduces muon rates by over four orders of magnitude.
- The shield's design achieves the necessary background suppression for the experiment.
- Performance simulations confirm the shield's capability to meet experimental requirements.

## Abstract

The SHiP experiment is designed to search for very weakly interacting particles beyond the Standard Model which are produced in a 400 GeV/c proton beam dump at the CERN SPS. An essential task for the experiment is to keep the Standard Model background level to less than 0.1 event after $2\times 10^{20}$ protons on target. In the beam dump, around $10^{11}$ muons will be produced per second. The muon rate in the spectrometer has to be reduced by at least four orders of magnitude to avoid muon-induced combinatorial background. A novel active muon shield is used to magnetically deflect the muons out of the acceptance of the spectrometer. This paper describes the basic principle of such a shield, its optimization and its performance.