3.4.2 Fireworks Tutorial

Getting started

WorkBookFireworks gives full set of instructions to get started. Here we just do the absolute minimum:

Linux box on FNAL network

/uscmst1/prod/sw/cmsshow/cmsShow22/cmsShow /uscmst1/prod/sw/cmsshow/cmsShow22/data.root

Linux box on CERN network

/afs/cern.ch/cms/fireworks/cmsShow22/cmsShow /afs/cern.ch/cms/fireworks/cmsShow22/data.root

Standalone Linux box

cd /tmp
wget http://cern.ch/cms-sdt/fireworks/cmsShow22.tar.gz
tar xzf cmsShow22.tar.gz
cd cmsShow22
./cmsShow data.root

Overview

The following 10 minutes video click gives clear introduction to the most basic aspects of the event display. (QuickTime player is required)

Video Introduction

• Demonstration of various views
• Adding and removing collections
• Usage of configuration files
• Event filtering

Physics Case

Drell-Yan (Z+jets)

In this example we will look at simulated Drell-Yan events from Fall08 Madgraph dataset: /ZJets-madgraph/Fall08_IDEAL_V9_v1/GEN-SIM-RECO. To demonstrate some important features of the event display we will look only at the events with at least one electron greater than 20GeV and missing-Et of the event greater than 30GeV. If you access original dataset files, you can limit events that you look at by typing

$Electrons.pt()>20&&$MET.pt()>30

in the event filter field. A small preselect data file can be downloaded from the web (~60Mb). No filtering is needed with this small file.

wget http://cern.ch/cms-sdt/fireworks/data/zjets_el20_met30.root

Drell-Yan events with Z->ee or Z->mumu have no natural sources of missing energy when missing Et is corrected for low response of muons in the calorimeter. Requiring one energetic electron we will see mostly Z->ee events.

Run 2 Event 7

It's a typical example of Z->ee+1jet, where jet calorimeter response underestimates the jet energy and leads to missing-Et well aligned with this jet. Put Rho-Phi view in the main view to see more better transverse energy balancing.

Run 2 Event 39

We see one electron not balanced by anything. To understand what happened, put Rho-Z view in the main view. Pay attention to the very forward region. You may find significant energy deposition there as well as GenParticle pointing toward it. Move your mouse over the particle line and you will get information about it: "gen e-, Pt: 15.9GeV" This is a case of limited tracker acceptance. The missing Et that we show here doesn't take into account very forward detector, which may lead to significant fake missing Et due to beam induced background.

Run 2 Event 175

Go to this event by typing 175 in the Event field. Switch to 3D view or Lego view as the main view. Here we see clearly a case of isolated electron and muon in the final state. To understand what happened here, we may look at the generator level information since it's available. Right click on the GenParticles item in the List View and you get the Collection controller. Let's specify that we only want to see leptons and neutrinos. In Filter type "abs(pdgId())>10&&abs(pdgId())<17". Now in Select you may try to highlight one by one different lepton types and they will be highlighted in all views. When you put abs(pdgId())==15, you would see 2 back to back tracks. So we have a case of Z->tau-tau, where one tau decays to e+2nus and the other to muon+2nus. Missing Et is aligned with muon due low response of muons in the calorimeter (MET was not corrected for muons).

Run 2 Event 443

2 muons and 2 electrons are reconstructed in this event. Opening list of muons and electrons in the list view and selecting them one by one, you may notice, that muon1 and electron1 are very close to each other and there is significant energy deposition in ECAL (red). The muon looks pretty good and it cannot radiate that much at this energy. So what do we have? It can be Z->mumugamma (internal radiation). Let's look at the generator level photons by filtering GenParticles with "pdgId()==22&&et()>10". Switch off electrons and muons to clean up the area and you will see 2 generator level photons pointing in the this area (why 2 not 1, it's a good questions to Madgraph experts).

Run 2 Event 487

Another case of Z->tautau->emu+4neutrinos.

Run 2 Event 20

Very nice example of fake missing Et due to jet energy underestimation in the calorimeter.

-- DmytroKovalskyi - 15 Jan 2009