Measurements of the HLT performance of displaced muons using Cosmics data (CMS Detector Performance Note)

This detector performance note documents crucial measurements we conducted to validate the trigger system used in the CMS search for displaced dimuons.

Using cosmic-ray muons recorded by the CMS detector in 2016, we measured how efficiently the High-Level Trigger (HLT) could identify muons that originated away from the central collision point. These measurements were essential for understanding the detector's sensitivity to long-lived particles decaying into muon pairs at displaced positions.

The results directly informed the design and optimization of a specialized double-muon trigger for the 2018 data-taking period, enabling searches for exotic particles beyond the Standard Model.

Key facts

  • Project: Detector performance measurements for the CMS search for displaced dimuons
  • Collaborations: CMS (CERN, Geneva, Switzerland)
  • Date: Sep 2019
  • Time invested: 1 year
  • Links:
  • Keywords: high-energy particle physics, long-lived particles, LLP, displaced muons, displaced dimuons, BSM physics, trigger efficiencies, CMS High-Level Trigger (HLT)

A cosmic-ray muon traversing the CMS detector

Abstract

This note presents the performance of a dedicated displaced standalone muon reconstruction at the High Level Trigger in cosmics data recorded with the CMS detector in 2016. The results are presented as a function of the impact parameter of the offline reconstructed muon. A double muon trigger based on this muon reconstruction has been developed for the search of long-lived particles decaying into dimuons with 2018 data. The trigger relies only on information from the muon detectors to allow sensitivity to decays beyond the inner tracking detector.