Basic objects challenge

Overview

Teaching: 0 min
Exercises: 30 min

Questions

• How should I construct selection criteria for a physics analysis?

Objectives

• Combine trigger, identification, and isolation information into a full selection for a specific physics process.

All of the trigger and physics object information from this lesson is combined when designing the event selection procedure for a physics analysis.

Workshop analysis example: \(t\bar{t} \rightarrow (bjj)(b\ell\nu)\)

Later in the workshop we will use a measurement of the top quark pair production cross section as an example analysis. The signal for this measurement is one top quark that decays hadronically, and one top quark that decays leptonically, to either a muon or an electron.

Your analysis example

What is a physics process that you might study? Let’s design a possible CMS event selection. If your process includes a particle with multiple possible decay modes, choose one (or a small group of very similar decay modes) as a test case for this challenge.

For the \(t\bar{t}\) measurement and/or your own process of interest, use the information you have gained about triggers and physics objects to sketch out a possible event selection for your analysis.

Signal

Which final state particles would you expect to observe in the detector from your “signal” process?

Based on these particles, consider:

• Which trigger or triggers would be useful to make sure your signal events are represented in the dataset?
• Which objects should you require in each event?
• What kinematic criteria might you requier for each object? (momentum, angular regions, etc)
• What quality criteria might you require for each object? (identification, isolation)
• Are there any correlations between your objects that you might exploit?

Background

Which SM backgrounds could easily mimic your signal, given a few extra physics objects, or a few missing physics objects?

Based on these processes, consider:

• Which background simulations should you include in your study?
• Should you apply any upper or lower limits on the numbers of certain physics objects in your events?
• Are there any objects you should veto from your events?
• What quality criteria might you choose for vetoing objects?

Solutions

In the final session for this lesson we will go over the actual analysis choices for the \(t\bar{t}\) measurement and discuss approaches for some physics processes you chose for this challenge.

Key Points

• Come back for the discussion session after the break!