Precise Mapping of the Magnetic Field in the CMS Barrel Yoke using Cosmic Rays

TL;DR

This paper presents a precise mapping of the magnetic field in the CMS detector's steel yoke using cosmic muon data, crucial for accurate physics event reconstruction in high-energy experiments.

Contribution

It introduces a method to accurately measure the magnetic field in the CMS steel yoke using cosmic ray muons, improving upon previous estimations.

Findings

Magnetic field in the steel yoke determined with 3-8% precision.

Cosmic muons effectively used for in-situ magnetic field mapping.

Enhanced accuracy in magnetic field maps for CMS detector simulations.

Abstract

The CMS detector is designed around a large 4 T superconducting solenoid, enclosed in a 12000-tonne steel return yoke. A detailed map of the magnetic field is required for the accurate simulation and reconstruction of physics events in the CMS detector, not only in the inner tracking region inside the solenoid but also in the large and complex structure of the steel yoke, which is instrumented with muon chambers. Using a large sample of cosmic muon events collected by CMS in 2008, the field in the steel of the barrel yoke has been determined with a precision of 3 to 8% depending on the location.