CMS DAS 2024 Tracking and Vertexing Short Exercise

CMS Detector Slice

Welcome to the CMS Data Analysis School 2024 Tracking and Vertexing Short Exercise!

We will present an introduction to using tracks for analyses in the era of large pile-up (many primary vertices). Our exercises will all use real data and will familiarize you with the following techniques:

Exercise Goals

  • Extracting basic track parameters and reconstructing invariant masses from tracks in CMSSW. Tracks are the detector entities that are closest to the four-vectors of particles: the momentum of a track is nearly the momentum of the charged particle itself.
  • Cleaning sets of tracks for analysis. We will use filters to eliminate bad tracks and discuss sources of tracking uncertainties. These filters are provided by the tracking POG (Physics Object Group)
  • Extracting basic parameters of primary vertices. In this high-luminosity era, it is not uncommon for a single event to contain as many as thirty to fifty independent collisions. For most analyses, only one is relevant, and it can usually be identified by its tracks.
  • Using tracks to measure from data and Monte Carlo (MC) samples the tracking efficiency by using tag and probe method via dimuon resonances. It can be extended to measure the efficiency of any selection of muons (trigger, isolation, identification) and derive scale factors from MC.

Prerequisites

Before going any further, please complete the CMS DAS Pre-Exercises and then follow the instructions on the setup page.

Facilitators

*Lead Contact


Daniel Spitzbart
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Michael Carrigan
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Aidan Grummer
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Keith Ulmer
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Kai Yi
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Irene Zoi
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Sam Bein
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Brunella D'Anzi
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Nicola De Filippis
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Ulascan Sarica
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Mattermost Chat

The Tracking and Vertexing Short Exercise channel will be available once you join the CMSDAS@LPC2024 team. Direction for how to join this Mattermost chat team can be found on the setup page.

CERN Twiki and Introduction Slides

The CERN TWiki of this short exercise can be found at this link. At the beginning of this short exercise an introduction will be done based on these slides.

Close-out Slides

You can find a guideline closeup for the Tracking and Vertexing Short Exercise questions and results on these slides.

Schedule

Setup Set-up your working environment
00:00 1. CMS Data Analysis School Tracking and Vertexing Short Exercise - The five basic track variables What are the main track variables used in CMS collaboration in different data formats?
How can we access them?
Which are the track quality variables?
How do the distributions of track variables before and after high purity track selection change?
00:30 2. CMS Data Analysis School Tracking and Vertexing Short Exercise - Tracks as particles Can we consider a track as a particle?
Can I use an alternative to the muon object?
Can I define the invariant mass of two tracks?
00:50 3. CMS Data Analysis School Tracking and Vertexing Short Exercise - Constructing vertices from tracks What is a (primary, secondary) vertex object? What about beamspot?
Which information are available in different CMS data formats?
How can I run the vertex reconstruction?
Can we get better physics results using primary verteces?
01:30 4. CMS Data Analysis School Tracking and Vertexing Short Exercise - Appendix How can I use track variables to retrieve the CMS tracking efficiency?
Can I find more about secondary vertex?
Is there a correlation between pile-up and number of clusters?
01:31 Finish

The actual schedule may vary slightly depending on the topics and exercises chosen by the instructor.