1. Flavour Physics in and beyond the Standard Model
Andreas Crivellin
Flavour Physics in and beyond the Standard Model
Supported by a Marie Curie Intra-European Fellowship of the European Community's 7th Framework Programme under contract number (PIEF-GA ).

2. “Missing Energy” Decays
Let’s now discuss “missing energy decays” and the excitement in this area.
Thanks to Tom Browder!

3. Outline: Introduction: The Standard Model of Particle Physics
Particle content
Interactions
Flavour physics in the SM
CKM Matrix
Flavour changing neutral currents
Hints for New Physics in flavor observables
Implications for New Physics 3

4. What are the smallest building blocks of matter and which forces act between them?4

5. Fundamental Matter Particles
Electrons
Quarks
Neutrinos
Super-Kamiokande
Point-like

6. Forces Gauge Theory (local symmetry) Interaction particles
Quantum field theory
Interaction particles

7. Feynman diagrams Visualize Interactions in Quantum Field Theory
Tree-level
1-loop

8. Quantum Electro Dynamics (QED)
U(1) gauge theory
Force Particle: Photon
Tested to extreme precision
E.g. anomalous magnetic moment of the muon calculated up to the 5-loop level (Kinoshita et al.)
2-loop Feynman diagrams for the anomalous magnetic moment

9. Quantum Chromo Dynamics (QCD)
Charge: color (only for quarks)
Force particle: gluon
SU(3) → 8 gluons
Asymptotic freedom
Prediction meson and hadrons
Essential for hadron colliders like the LHC
Pertubative and non-perturbative effects in flavor physics

10. Gravitation (General Relativity)
Force is curvature of space time
How to quantize it? Graviton?
Not part of the Standard Model (and this talk)

11. The weak force SU(2) gauge group acting only on left-handed fermions
Charge: component of the SU(2) doublets
Charged (W) and neutral (Z) currents
Weak because the gauge bosons are massive

12. The Higgs Boson and Electroweak (EW) Symmetry Breaking
One complex scalar doublet in the standard model (4 degrees of freedom)
Three components give masses to Z and W
Only one physical component remains: The Higgs particle
Generates masses after EW symmetry breaking

13. The Higgs boson
Couples to EW gauge bosons and fermions proportional to their masses
Tree-level production in proton-proton collisions suppressed
The first and only particle ever observed produced via quantum loop effects.
Standard Model of particle physics in now complete

14. The Standard Model

15. New Physcis?
The Standard Model works up to the 100 GeV scale (10-18 cm)
But:
Why are neutrinos nearly massless?
Are fermions, the Higgs and the gauge bosons fundamental particles?
Why is the electric charged quantized?
What about gravitation?
More CP violation to generate (anti) matter asymmetry?
Hierarchy Problem: SUSY? Extra dimensions?
Are there new heavy particles?

16. Flavour Physics in the SM16

17. Light Mesons

18. Bottom Mesons

19. Yukawa Interactions and fermion masses
Interactions of the Higgs particle with fermions
The quarks acquire masses after electroweak symmetry breaking
Diagonalized by biunitray transformations
Only the charged W vertex is flavor changing

20. The CKM matrix CKM matrix
The mass matrices are diagonalized by (bi) unitary transformations
Neutral gauge interactions are proportional to the unit matrix etc.
Only the W vertex is flavour changing in the SM.
CKM matrix

21. Tree-level determination of the CKM elements
Vub
Vcb
Vus
Kaon decays

22. NP in CKM elements?
Inclusive and exclusive determinations of the Vub and Vcb do not agree well.
Right-handed W-b-u coupling?
Update of AC, S. Pokorski, PRL (2014) 
No new physics in CKM elements, i.e. SM problem

23. Magnitude of the CKM elements (tree-level)
Vud from beta decay
Vcd and Vcs from D decays
Vtb, Vtd and Vts determined by CKM unitarity
Vtb also from t→Wb but not competitive

24. Flavour Changing Neutral Current (FCNC) processes24

25. FCNCs
Absent in the SM at tree-level as all flavor violation comes from the CKM matrix in the charged the W-quark
Involve small off-diagonal CKM elements
Induced at the 1-loop level by quantum fluctuations suppressed by the large W mass
Very suppressed in the SM
Maybe large in theories beyond the SM
Excellent place to search for heavy New Physics

26. ΔF=2 processes Particle anti-particle oscillations Mass difference
CP violation
Agree well with the SM within uncertainties
Test NP up to 10,000 TeV

27. Global CKM Fit
Indirect and direct determinations agree very well

28. B→Xsγ Inclusive decay Complete perturbative calculation
Misiak et al
SM and experiment agree very well
Test of chirality changing new physics

29. Hints for New Physics in the Flavour Sector29

30. B→K*µµ Semi-leptonic decay form factor dependence
Clean observables are (approximately) free of hadronic uncertainties 27
2-3 σ deviation from the SM mostly in P5’

31. B→K*µµ Can be explained by a NP contribution to the operator
New physics explanation is not easy (MSSM, 2HDM do not work).
Most natural explanation:
Neutral gauge boson (Z’)
Leptoquarks
Subleading hadronic effects might be larger than expected…
Further supported by Bs→ϕμμ
R. Horgan, Z. Liu, S. Meinel, and M. Wingate (2015),
 arXiv: 28

32. R(K) = B→Kµµ/B→Kee Lepton flavour universality violation
2.6 σ deviation from the theoretically rather clean SM expectation
Also lepton flavour violation? 29

33. Global fit to b→sμμ data
Global analysis give a very good fit to data
Symmetry based solutions give a very good fit to data:
W. Altmannshofer, D. M. Straub, arXiv: T. Hurth, F. Mahmoudi, and S. Neshatpour, Descotes-Genon et al 30
Fit is 4-5 σ better than in the SM

34. Tauonic B decays Explained by a charged Higgs or leptoquarks
Tree-level decays in the SM via W-boson
Lepton flavor violation in the charged current
Explained by a charged Higgs or leptoquarks 34

35. Extended Higgs sector at the EW scale
CMS and ATLAS finds 2.6 σ difference from zero
Lepton flavour violation
Large branching ratio
Extended
Higgs sector
at the
EW scale 8

36. Explanations of the Flavour Anomalies
Additional neutral gauge bosons (Z’)
Extended Higgs sector
Leptoquarks 5

37. Z’ models with gauged
AC, G. D‘Ambrosio and J. Heeck
Explaining B→K*μμ, R(K) and h→τμ in a two-Higgs-doublet model with gauged Lμ-Lτ
arXiv: , PRL 114 (2015)
Adressing the LHC flavour anomalies with horizontal gauge symmetries
Phys.Rev. D91 (2015) 7, 37

38. B→K*µµ, R(K)
Bs mixing
allowed regions 38

39. and 39

40. LHC limits 40

41. Conclusions
The CKM mechanism of flavor violation has been confirmed with high precision
Flavor physics is an excellent testing ground for physics beyond the SM: It test NP indirectly via quantum fluctuations Complementary to direct LHC searches
Deviations from the SM were observed in B and Higgs decays. Is lepton flavor (universality) violated?
Extended Higgs sector?
Leptoquarks?
New gauge bosons? 41

42. Type X 2HDM with perturbations42

43. 2HDM of type X + corrections
Allow for additional couplings
The parameters describe flavor-changing neutral Higgs interactions which we assume to be of the form

44. 44

45. 45

46. Branching ratio can even reach the percent level46

47. No simultaneous explanation without
fine-tuning 47