CMS Masterclass Introduction
The CMS masterclass is a way for students to be "particle physicists for a day" using authentic data from the Compact Muon Solenoid (CMS) experiment in the Large Hadron Collider (LHC) at CERN. The outline below shows how it works and what the tools are.

Enduring Understandings


Recommendations for a Successful CMS Masterclass

Students should remember long after the masterclass:
  1. Particle physics research requires the use of indirect evidence to support claims.
  2. The Standard Model is the current theoretical framework for our understanding of matter.
  3. The behavior of particles is governed by conservation laws and mass-energy conversion.
How we try to go about it:

  • Engaging, interactive event displays
  • Actual events from CMS
  • Analysis of authentic data requires judgement and asking good questions
  • Stress probability, statistics, signal vs. background
N students where N≤30

The optimal number of students is about 30 or fewer. It is possible to have more but please proceed cautiously.
N/2 computers

Two students to a computer: they can help each other and check each other's judgements.
N/10 mentors or tutors

At least one physicist to every 10 students. In some cases, a teacher with a developed background in masterclasses can help bend this ratio.


Main Measurement Tool: iSpy event display

Versions in use for International Masterclasses

"Classic" iSpy:

Advanced iSpy: (recommended, fully supported)

Use case:
  • CMS Masterclass WZH path. Students search for dilepton, 4-lepton, and single-lepton plus missing ET (W candidate) events. Students find ratios of W+ to W- and e to μ; they make 2- and 4-lepton mass plots to find the Z and any other resonances that may become apparent.

Data Analysis:

Low bandwidth: Download local event display and data.
Other Versions

Use cases:
  1. CMS Masterclass J/Ψ path. Students rate dimuon events by quality of tracks to create a mass plot that best eliminates background while preserving the signal that shows the J/Ψ meson mass.
  2. CMS World Wide Data Day measurement. Students measure the directions of muon tracks in dimuon events they select to make angular distributions of muon tracks. They use this to understand particle tracks in CMS and the LHC.

Data Analysis:

Low bandwidth: Download local version.