1. LHCb Masterclass measurement of the Dº lifetime Ana Trisovic on behalf of the LHCb collaboration 37 th International Conference on High Energy Physics

2. International Masterclasses Discovery of Particle Physics for high- school students Lectures, exercises and computer applications for the visualization and calculation of physical phenomena For the first time with the LHCb Measurement 2 LHCb statistics: 7 days of LHCb MC 20 institutes ~600 students th Edition in 2014

3. 10% of LHC interactions produce a charm hadron - collected more than 1 billion signal charm decays Measuring the Dº Lifetime The Dº Meson Dº meson Charm quark Up anti- quark K- pi+ 10 ps (and even longer) inside the experiment v ≈ 0.99919 · c s = ~ 0.12 + ~ 3 mm 3 Lifetime at rest: 0.41 ps ~3.9%

4. Signal finding Appearance of the Event Display 4

5. Functionality Projections Close-up view 5

6. Signal finding Step 1: The goal is to find a D° particle in the event, which decays K- and pi+ 6

7. Step 2: Calculating invariant masses Step 3: Building up the histogram Combining all the histograms + discussion 7

8. Demonstration 8

9. Lifetime fit Requires a large number of events for reasonable accuracy ~15% off We have a systematic bias 9

10. Two types of data: Effect of IP cut: Lifetime fit p p D° pi+ K- p p D° pi+ K- B IP The final result 10 PDG lifetime

11. Users’ feedback High interest from the students –Many questions about CERN Great success! Very positive feedback! 11

12. Technical details Data: 2011 - 2012 data-taking Developed in MS Visual Studio 2012 Programming languages: –ROOT –C++ General requirements: ROOT and Cmake Need to make the software as easy and portable as possible –Collaboration with CERN Media Lab 12

13. Total Event Visualizer Scientific discovery tool for general public Based on computer gaming technology Suitable for multiple platforms including Windows, Mac OS, Android, web browser… 13

14. LHCb in TEV 14

15. Thank you for your attention! For more info: http://lhcb-public.web.cern.ch/lhcb-public/en/LHCb-outreach/masterclasses/en/