1. By Rudin Petrossian-Byrne Supervisors: Dr. Marco Gersabeck & Stefanie Reichert CERN Summer Student Programme 2014

2. Before The Physics…. Hi! My name is Rudin from Dublin studying Physics ( Undergraduate )

3. Rudin Petrossian-Byrne CERN 2014 3 The big picture Mixing and CPV

4. Rudin Petrossian-Byrne CERN 2014 4 The big picture Mixing and CPV Mixing

5. Rudin Petrossian-Byrne CERN 2014 5 The big picture Mixing and CPV Mixing me

6. Rudin Petrossian-Byrne CERN 2014 6 The big picture Mixing and CPV with Charm  2007 – First Evidence from BaBar and Belle for mixing in charmed neutral mesons Charm Quark  No significant evidence for CPV in charm to date Mixing parameters very small SM ‘predicts’ small CPV Observation at current sensitivity would imply New Physics R Phys. Rev. Lett. 110 (2013) 101802

7. Rudin Petrossian-Byrne CERN 2014 7 Allows measuring x and y parameters directly

8. Rudin Petrossian-Byrne CERN 2014 8 Allows measuring x and y parameters directly PP  Protons collide in the VELO Detected by TT tracker. Bend through magnet. Detected by T1, T2, T3.

9. Rudin Petrossian-Byrne CERN 2014 9 Allows measuring x and y parameters directly  3-Body Decay Unlike 2-body decays, energy of daughter particles not well-defined Range of possible values. LHCb Simulation

10. Rudin Petrossian-Byrne CERN 2014 What we observe: Dalitz plot is characterised by Resonances + non-resonant background 10 Not homogenously populated with events Some daughter energies more probable LHCb Simulation

11. Rudin Petrossian-Byrne CERN 2014  Approximate by a relativistic Breit–Wigner probability distribution function 11 THE ISOBAR MODEL Great for isolated Resonances!

12. Rudin Petrossian-Byrne CERN 2014 PROBLEM Not good Theorists are unhappy 12 Should probably do something about that… Great for isolated Resonances! BAD for overlapping resonances Curtis A. Meyer, Carnegie Mellon University, ‘A k-matrix tutorial’ (2008)

13. Rudin Petrossian-Byrne CERN 2014 ALTERNATIVE MODEL 13

14. Rudin Petrossian-Byrne CERN 2014 K-Matrix Formulation 14 Upholds unitarity by construction! Curtis A. Meyer, Carnegie Mellon University, ‘A k-matrix tutorial’ (2008) ─Breit-Wigner ─K-matrix ─Breit-Wigner ─K-matrix

15. Rudin Petrossian-Byrne CERN 2014 Implementation: CODING Running on a GPU (Graphical Processing Unit) 15

16. Rudin Petrossian-Byrne CERN 2014 What are we fitting to data? 21 floating variables 16 LHCb Simulation Need to fit

17.  Wrestling with errors Rudin Petrossian-Byrne CERN 2014 17 STATUS  This Week: Code Working on a CPU!  GPU memory issues currently being addressed

18. Rudin Petrossian-Byrne CERN 2014 18 THANK YOU Questions?

19. Rudin Petrossian-Byrne CERN 2014 19 Spare Slides

20. Rudin Petrossian-Byrne CERN 2014 What are we fitting to data? 21 floating variables 20 Sum over polesNon resonant termCorrection term

21. Rudin Petrossian-Byrne CERN 2014 21

22. Rudin Petrossian-Byrne CERN 2014 22

23. Rudin Petrossian-Byrne CERN 2014 23 Onto the Physics…. Isobar model K-matrix Detection Dalitz Plot & Resonances