minerva, feb 9, 2011monika wielers (ral)1 minerva abreviation for masterclass involving event...

Minerva, Feb 9, 2011 Monika Wielers (RAL) 1

MinervaAbreviation for

Masterclass INvolving Event Recognition Visualised with Atlantisdeveloped and 1st used in 2008 Masterclasses at RALAims:

Learn about ATLAS and the LHCLearn how to identify particles in the ATLAS detectorunderstand how we can deduce from final state particle (electrons, muons, jets, missing energy) the particles produced during the collision

Tools Use slightly simplified version of the ATLAS event display program Atlantis

Since 2008 exercise used in various Masterclasses in the UK, US and CanadaWeb page

http://atlas-minerva.web.cern.ch/atlas-minerva/




RAL Masterclass

Basic idea:

Analyse 20 event displays and classify them according to the following categories

WeWZee

ZJets

In addition, to add some more fun to it and as ATLAS is a discovery machine, one H4l events is present

Group who finds it will get a prize at the end of the exerciseCalculate ratios of We/W, Zee/Z, W/Z

Exercise takes around 1hSo far simulated events were used for 2011 data events are available


Set-up

PrerequisiteJava version > 1.6

Download Atlantis including the event displays fromhttp://www.ep.ph.bham.ac.uk/twiki/bin/view/General/MinervaResourcesZip file for 15 and 20 groups available

Unzip and click on atlantis.jar file to start programmeWorks under Windows, Mac and linux

Even pretty old ones

No network connection needed

http://www.ep.ph.bham.ac.uk/twiki/bin/view/General/MinervaResources

http://www.ep.ph.bham.ac.uk/twiki/bin/view/General/MinervaResources


•End-on view of the detector (x-y projection)

•Warning: Only particles reconstructed in central region shown here (otherwise the particles in the forward would cover the view)!

•Side view of the detector (R-z projection)

•Particles in central and forward region are shown


Introduction

Explain how to identify different types of particlesevent displays for We, W, Zee, Z, jet

Experience: Most difficult part is e/jet separationhow to use atlantis

The students have the same events on their computer, so the latter two parts can be done in common


Exercise

Every student get 20 events with a mixture of We, W, Zee, Z, QCD di-jet events

Group 1: evt 1-20, group 2: evt 21-40 etc

Mixture of W and Z in the right proportion (on average 10 W, 1 Z) , however, less QCD background events than in ‘real life’ (~40%)

Each group of students start with a W or Z event

First events are more easy and then they become successively more complicated

Students then go through the events one by one and classify them

Tutors help them to use Atlantis and show in a given event how to figure out if you deal with e, , jet

Help typically only needed for the first events

People who finish can look at the rest of the events and hunt for the Higgs/prize


Wrap-up

Collect results from each groupDone in excel sheet (avoids network connection)

Calculate ratio of We/W, Zee/Z and W/ZCompare with expectationsExplain principle of lepton universality

Ask people who found Higgs to tell you the event number

Display the event from your computer for everyone

If correct give (small) prize, i.e. ATLAS pen, CERN card game…


Example: We

Electron

EM cluster

track

Missing transverse energy

“arrow width“ is a measure of its magnitude

Value directly displayed


Example: Z

Muon

Track in inner detector

Track in muon detector


Example: Jet, what‘s difficult about it


Typical Atlantis command used

Pick button Display track

momentum by clicking on track

Next buttonGo to next event


Wrap-up

We/W, Zee/Z works out pretty well, most groups end up with number within errorW/Z ratio typically too low, students tend to migrate W into Z events


Some pictures


Observations

Students need some help to get going too many new things to deal withOnce they know what they do they are doing they only need help for ‘difficult’ events

No problem for the student to use Atlantis event display programmeThey often try out more command than they were taught

How ‘fast’ students scan the events depended on having/not having the introductory lecture explaining how to identify particles

20 events to classify seems to be the right amount

by then students have understood well what to do

More events would imply students start to be bored

When they finished most of the groups started looking for the Higgs rather than looking at the detector displays

No one got bored (unless they were not interested at all) or started disturbing the rest!

Atlantis runs very reliably, no glitches at all


Feedback

Students are most enthusiastic about the Higgs hunting part

Students enjoy using the same programme as used by physicists

Several teachers commented the level of difficulty is just right

By now quite some students participating in the Masterclass at RAL commented this was the best part of the day

Quite a success considering the visit to Diamond/ISIS facilities are the highlight of the day


Web based Minerva version


This version is completely web based

It contains online tutorial

Using 5 test events the student can check if he understood the basics

Result sheet will tell him how many events he/she got right

20 events to analyse (incl. one Higgs event)

After analysis, results checked online

Compared to Masterclass the even displays used are “easy“ ones

This application is also suited for classroom usage or younger students (14-15 years)

Available in English and French

Examples in the next pages




Online Tutorial


Result sheet and online verification


Summary and Outlook

Minerva Masterclass successfully run since 2008

So far used by various UK as well as US and Canandian groups

very well received by students and teachers

Depending on time this exercise can be complemented by other ATLAS based Atlantis exercises, e.g. W+/W- ratio, Z mass reconstruction etc.

This year data is used (besides the Higgs event)

Data files available on website

documentation is still being updated

minerva, feb 9, 2011monika wielers (ral)1 minerva abreviation for masterclass involving event...

Documents

z eventfirst events

data events

h4l events

simulated events

event recognition

event numberdisplay

qcd background events

given event