Validation of the CMS Magnetic Field Map

TL;DR

This paper validates the CMS magnetic field map by comparing a detailed 3D model with extensive measurements taken around the CMS detector's steel yoke, ensuring accurate magnetic field characterization for physics analyses.

Contribution

It presents a comprehensive comparison between a TOSCA 3D magnetic field model and actual measurements in the CMS detector's steel yoke, validating the field map used in experiments.

Findings

The TOSCA model accurately describes the magnetic field outside the tracking volume.

Measurement data agrees well with the model within known uncertainties.

Validation supports reliable magnetic field knowledge for CMS physics analyses.

Abstract

The Compact Muon Solenoid (CMS) is a general purpose detector, designed to run at the highest luminosity at the CERN Large Hadron Collider (LHC). Its distinctive features include a 4 T superconducting solenoid with 6-m-diameter by 12.5-m-length free bore, enclosed inside a 10,000-ton return yoke made of construction steel. The return yoke consists of five dodecagonal three-layered barrel wheels and four end-cap disks at each end comprised of steel blocks up to 620 mm thick, which serve as the absorber plates of the muon detection system. To measure the field in and around the steel, a system of 22 flux loops and 82 3-D Hall sensors is installed on the return yoke blocks. A TOSCA 3-D model of the CMS magnet is developed to describe the magnetic field everywhere outside the tracking volume measured with the field-mapping machine. The magnetic field description is compared with the measurements and discussed.