13 TeV Collision Events

Overview

Teaching: 60 min
Exercises: 30 min

Questions

Objectives

In this section, we will look at collision events at 13TeV. These events are selected from SingleElectron and SingleMuon datasets. The events with two or more leptons are selected.

There are a few relevant files. Open the single electron data file, /eos/uscms/store/user/cmsdas/2020/short_exercises/Visualization/data_SingleElectron.root

Go to event 274200:48:72793234

Question 15

What kind of event is this? How can you justify your answer?

Show/Hide

This is a probably a Z->ee event, as can be understood from the invariant mass of the two electrons (90.647 GeV).

Go to event 274200:48:71915470

Question 16

What kind of event is this? How can you justify your answer?

Show Answer

The invariant mass of the two electrons (84.667 GeV) and that of the two jets (104.962 GeV). This could even be a ZZ->2e2q event, although this process is extremely rare with respect to the more frequent Z+2jets.

Go to event 274200:48:72636084

Question 17

What kind of event is this? How can you justify your answer?

Show Answer

This is probably a Z+jet event, as can be understood from the invariant mass of the two isolated electrons (90.312 GeV).

Hint: Isolation can be accessed via (i.userIsolation(\"PfChargedHadronIso\")+i.userIsolation(\"PfNeutralHadronIso\")+i.userIsolation(\"PfGammaIso\"))/i.pt() The 2nd electron with very high isolation value is likely part of a quark or gluon (i.e. ISR).

Often we find events that are not trivial to interpret, and usually there are at least a couple of processes which could have generated the event. If you got this far in the exercise you have enough experience to look at some more difficult events and try to guess what they come from. Typical questions to address are: how many AK4 jets are there in this event? Are they all isolated from leptons? Are they b-jets? Are there any electrons in the event with pt>30GeV? If so, check their isolation. Are there any muons in the event with pt>30GeV? If so, check their isolation. Is this a single lepton event? If so, what is the lepton? Can you identify any likely top candidates?

Question 18/19

Look at some interesting events in this dataset and try to interpret them: 1023/1523919869, 1023/1523757530.

You can also explore the single muon data file /eos/uscms/store/user/cmsdas/2020/short_exercises/Visualization/data_SingleMuon.root

You can go through the events and characterize each based on the objects you find.

If you have time at the end (after the next section), explore the events stored in

/eos/uscms/store/user/cmsdas/2020/short_exercises/Visualization/SinglePhoton*.root, and see if you can find anything interesting.

Key Points