Minerva Masterclass: Discovering Particle Physics with Atlantis

1. Minerva • Abreviation for • Masterclass INvolving Event Recognition Visualised with Atlantis • developed jointly by RAL and Birmingham and first used in 2008 Masterclasses at RAL and Birmingham • Aims: • Learn about ATLAS and the LHC • Learn how to identify particles in the ATLAS detector • understand how we can deduce from final state particle (electrons, muons, jets, missing energy) the particles produced during the collision • Tools • Use ATLAS event display program Atlantis with slightly simplified configuration file • Since 2008 exercise used in various Masterclasses in the UK, US and Canada • Web page • http://atlas-minerva.web.cern.ch/atlas-minerva/ Monika Wielers (RAL)

2. Minerva Masterclass • Basic idea: • Analyse 20 event displays and classify them according to the following categories • We • W • Zee • Z • Jets • Note, each group analyses a different event sample • Above done after introduction and test example for each event category • In addition, to add some more fun to it and as LHC is a discovery machine, one H4l event is present • Group who finds it will get a prize at the end of the exercise • Calculate ratios of We/W, Zee/Z, W/Z • Exercise takes around 1h • So far simulated events were used - For 2011 data events are available Monika Wielers (RAL)

3. Set-up • Prerequisite • Java version of at least Java 1.6 installed • Download Atlantis including the event displays from • http://www.ep.ph.bham.ac.uk/twiki/bin/view/General/MinervaResources • Zip file for 15 and 20 groups available • Untar and click on atlantis.jar file to start programme • Works under Windows, Mac and Linux • Even pretty old ones • No network connection needed Monika Wielers (RAL)

4. 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 Monika Wielers (RAL)

5. Introduction • Explain • How to identify different types of particles • Electrons, muons, missing transverse energy and jets • Event displays for We, W, Zee, Z, jet • Experience: Most difficult part is e/jet separation • How to use atlantis • As the students have the same tutorial events on their computer, possibility that they execute the same Atlantis commands as done in the introductory slides Monika Wielers (RAL)

6. Exercise • Every student get 20 events with a mixture of We, W, Zee, 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 Monika Wielers (RAL)

7. Wrap-up • Collect results from each grouo • Improve statistics by combining the event totals • Done in excel sheet (avoids network connection) • Calculate ratio of We/W, Zee/Z and W/Z • Compare with expectations • Explain 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… Monika Wielers (RAL)

8. Electron EM cluster track Example: We Missing transverse energy • “arrow width“ is a measure of its magnitude • Value directly displayed Monika Wielers (RAL)

9. Muon Track in inner detector Track in muon detector Example: Z Monika Wielers (RAL)

10. Missing ET We, ? Example: Jet Track and cluster • Track(s) in inner detector • EM calorimeter deposit • Hadronic calo deposit ignored • Electron, thus We Distinction that jet has EM and HAD energy and electron only EM energy is difficult for students Monika Wielers (RAL)

11. Typical Atlantis command used Pick button • Display track momentum by clicking on track Next button • Go to next event Monika Wielers (RAL)

12. Wrap-up • We/W, Zee/Z works out pretty well, most groups end up with number within error • W/Z ratio typically too low, students tend to migrate W into Z events Monika Wielers (RAL)

13. Some pictures Birmingham Masterclass 2010 RAL Masterclass 2008 RAL Masterclass 2009 Monika Wielers (RAL) Researchers Night 2010, CERN

14. Observations • Students need some help to get going • too many new things to deal with • Once 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 programme • They often try out more commands 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 • No one gets bored (unless they were not interested at all) and/or starts disturbing the rest! • Atlantis runs very reliably, no glitches at all Monika Wielers (RAL)

15. 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 Monika Wielers (RAL)

16. Web based Minerva version • http://atlas-minerva.web.cern.ch/atlas-minerva/ • 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 event 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 Monika Wielers (RAL)

17. Online Tutorial Monika Wielers (RAL)

18. Result sheet and online verification Monika Wielers (RAL)

19. Summary and Outlook • Minerva Masterclass programme is a joint development between RAL and Birmingham • Minerva Masterclass successfully run since 2008 • First use in Masterclasses at RAL and Birmingham • 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 events will be used (besides the Higgs event) • Data files available on website • documentation is still being updated • If you are interested, consult • http://atlas-minerva.web.cern.ch/atlas-minerva/ Monika Wielers (RAL)