1. Andreas Crivellin
New Physics
in the
Flavour Sector

2. Outline: Introduction: Flavour anomalies
Possible New Physics Explanations Z’
Extended Higgs sector
Leptoquarks
Simultaneous Explanations of Anomalies
Conclusions 2

3. Flavour Anomalies 3

4. b→sμμ Global analysis give a very good fit to data
Lepton Flavour Universality Violation
Symmetry based solutions give a very good fit to data:
See talk of Christoph Bobeth 4
Fit is 4-5 σ better than in the SM

5. Z’ explanations allowed regions U. Haisch et al. 1308.1959
W. Altmannshofer et al
A. C. et al
…..
allowed regions 5

6. Leptoquarks
Only weak constraints from other flavour observables (loop compared to tree)
Possible effect in the anomalous magnetic moment of the muon
Large production cross section at the LHC 6

7. Tauonic B decays Combined ≈4 σ deviation
See talk of Zoltan Ligeti
Tree-level decays in the SM via W-boson
Combined ≈4 σ deviation 7

8. R(D) Explanations Leptoquark (scalar or vector)
Charged Higgs different differential distribution
W’ ??? 8

9. 2.6 σ difference from zero 9

10. No dominant contribution from vector-like fermions
Can be explained in the effective field theory approach by
No dominant contribution from vector-like fermions
A. Falkowski, D. M. Straub, and A. Vicente,
Extended Higgs sector
R. Harnik, J. Kopp, and J. Zupan,
G. Blankenburg, J. Ellis, and G. Isidori,
S. Davidson and P. Verdier,
J. Heeck et al
A. Greljo et al. arXiv:
A. C. et al. arXiv:
...... 10

11. Models for Simultaneous Explanations of Anomalies11

12. 2HDM with gauged
Vectorial U(1) gauge group: Q(e) = 0, Q(μ) = 1, Q(τ) = -1
b-s couplings generated with vector-like quarks
Two Higgs doublets
Yukawa couplings
diagonalizes the τ-μ block of the mass matrix 12

13. 2HDM with gauged Lμ-Lτ 13

14. Leptoquark Explanations of b→sμμ and B→ D(*)τν
Tree-level contribution to but loop effect in
can explain
Anarchic flavor structure
Tree-level contribution to and
Hierarchical flavor structure, large third generations couplings, small first and second ones.
M. Bauer, M. Neubert arXiv:

15. Tree-level Leptoquark Explanation
Third generation couplings
Misalignment between interaction and mass basis
L. Calibbi, A.C. and T. Ota, PRL, arXiv:

16. 2HDM of type X
One Higgs doublet couples only to quarks the other Higgs doublet to leptons.
Additional free parameters:
Couplings to leptons are tan(β) enhanced

17. AC, Julian Heeck, Peter Stoffer. arXiv:1507.07567. PRL 201617
AC, Julian Heeck, Peter Stoffer. arXiv: PRL 2016

18. Prediction: Branching ratio can even reach the percent level
AC, Julian Heeck, Peter Stoffer. arXiv: PRL 2016 18

19. Conclusions
Extended Higgs sector
Z’ gauge boson
Leptoquarks

20. No simultaneous explanation without
fine-tuning 20