1. Minerva, Feb 9, 2011Monika Wielers (RAL)1 Minerva Abreviation for Masterclass INvolving Event Recognition Visualised with Atlantis developed and 1 st used in 2008 Masterclasses at RAL 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 slightly simplified version of the ATLAS event display program Atlantis Since 2008 exercise used in various Masterclasses in the UK, US and Canada Web page http://atlas-minerva.web.cern.ch/atlas-minerva/

2. Minerva, Feb 9, 2011Monika Wielers (RAL)2 RAL Masterclass Basic idea: Analyse 20 event displays and classify them according to the following categories W  e W  Z  ee Z  Jets In addition, to add some more fun to it and as ATLAS is a discovery machine, one H  4l events 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

3. Minerva, Feb 9, 2011Monika Wielers (RAL)3 Set-up Prerequisite Java version > 1.6 Download Atlantis including the event displays from http://www.ep.ph.bham.ac.uk/twiki/bin/view/General/MinervaResou rces Zip file for 15 and 20 groups available Unzip and click on atlantis.jar file to start programme Works under Windows, Mac and linux Even pretty old ones No network connection needed

4. Minerva, Feb 9, 2011Monika 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

5. Minerva, Feb 9, 2011Monika Wielers (RAL)5 Introduction Explain how to identify different types of particles event displays for W  e, W , Z  ee, Z , jet Experience: Most difficult part is e/jet separation how to use atlantis The students have the same events on their computer, so the latter two parts can be done in common

6. Minerva, Feb 9, 2011Monika 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

7. Minerva, Feb 9, 2011Monika Wielers (RAL)7 Wrap-up Collect results from each group 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…

8. Minerva, Feb 9, 2011Monika Wielers (RAL)8 Example: W  e Electron EM cluster track Missing transverse energy “arrow width“ is a measure of its magnitude Value directly displayed

9. Minerva, Feb 9, 2011Monika Wielers (RAL)9 Example: Z  Muon Track in inner detector Track in muon detector

10. Minerva, Feb 9, 2011Monika Wielers (RAL)10 Example: Jet, what‘s difficult about it

11. Minerva, Feb 9, 2011Monika Wielers (RAL)11 Typical Atlantis command used Pick button  Display track momentum by clicking on track Next button Go to next event

12. Minerva, Feb 9, 2011Monika 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

13. Minerva, Feb 9, 2011Monika Wielers (RAL)13 Some pictures

14. Minerva, Feb 9, 2011Monika Wielers (RAL)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 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

15. Minerva, Feb 9, 2011Monika 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

16. Minerva, Feb 9, 2011Monika 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 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

17. Minerva, Feb 9, 2011Monika Wielers (RAL)17 Online Tutorial

18. Minerva, Feb 9, 2011Monika Wielers (RAL)18 Result sheet and online verification

19. Minerva, Feb 9, 2011Monika Wielers (RAL)19 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