1. Explaining the flavour anomalies with Leptoquarks
Andreas Crivellin
Theory Group of the Laboratory for Particle Physics
Explaining the flavour anomalies with Leptoquarks
La Thuile,

2. Outline Introduction: Flavour anomalies
b→sμ+μ-
b→cτν aμ
Simultaneous explanations with leptoquarks
2 scalar leptoquarks
Vector leptoquark
Conclusions and outlook
Talks of Gudrun, Andrew and Johannes
Andreas Crivellin

3. Global fit to b→sμμ data
Flavour changing neutral current
Global analyses give a very good fit to data
B. Capdevila, AC, S. Descotes-Genon, J. Matias and J. Virto, arXiv: [hep-ph].
Fit is 5-6 σ better than the SM

4. All measurements above the SM prediction ≈4σ deviation
b→cτν processes
All measurements above the SM prediction ≈4σ deviation

5. Muon Anomalous Magnetic Moment
Single measurement from BNL
Theory prediction sound but challenging because of hadronic effects.
Soon new experimental results from Fermilab
3 σ deviation (order of SM-EW contribution)

6. Leptoquarks Scalars or Vectors
Talk of Gudrun
Scalars or Vectors
5 gauge representations each which are invariant under the SM gauge group
Couple quarks to leptons
Maybe also quarks to quarks
Proton decay
Are present in Grand Unified Theories

7. aμ: Leptoquarks
mt/mμ enhancement 8

8. Z→μμ at future colliders
Leptoquarks in aμ
Chirally enhanced effects via top-loops
Left-, right- handed muons-top coupling
E. Leskow, A.C., G. D'Ambrosio, D. Müller arXiv:
Z→μμ at future colliders 8

9. Two Scalar Leptoquarks for b→cτν
scalar leptoquark singlet with Y=-2/3
scalar leptoquark triplet with Y=-2/3
AC, D. Mueller, T. Ota arxiv:
Constructive in R(D(*))
Destructive in b→sνν

10. R(D(*)), b→sνν with 2 Scalar LQs

11. very strongly enhanced
R(D(*)) and b→sττ
Large couplings to the second generation
Cancelation in b→sνν needed: C(1)=C(3)
b→sττ
very strongly enhanced
Capdevila, AC, Descotes-Genon, Matias
See also R. Alonso, B. Grinstein and J. Martin Camalich,

12. R(D(*)), b→sμμ and aμ with 2 scalar LQs
Scalar leptoquark singlet + triplet with Y=-2/3
Cancelation in b→sνν imposed
2 out of 3 can be explained

13. Vector Leptoquark SU(2) Singlet
C9=-C10 effect in b→sμμ
Left handed vector current in R(D) and R(D*)
No effect in b→sνν
No proton decay
Contained within the Pati-Salam model
Massive vector bosons
Non-renormalizable without Higgs mechanism
Pati Salam not possible at the Tev scale because of KL→μe and K→πμe
Good solution, but difficult UV completion

14. Pati-Salam + vector-like fermions
Avoids bounds from KL→μe and K→πμe with
3 light generation (SM fermions)
3 heavy generation (vector like)
Only the LQ couples flavour violating

15. R(D(*)) and b→sμμ LHCb bounds require additional heavy
neutral fermions
Simultaneous explanation possible!
Can also account for the AMM of the muon

16. Pati-Salam + Randall-Sundrum
M. Blanke, AC, arXiv:
broken to the SM via boundary conditions on a compact extra dimension
Zero modes: SM fermions
KK modes: Vector-like fermions and massive gauge bosons
No zero mode for the Leptoquark
Flavour alignment to the down-sector
PS + RS naturally accounts for a vector LQ + VLFs

17. D mixing τ→μμμ and cannot be avoided
Flavour effects
b→cτν
b→sμμ
τ → μμμ & D mixing
D mixing τ→μμμ and cannot be avoided

18. Modell well motivated + limited but sizable effect
PS+RS Phenomenology
Modell well motivated + limited but sizable effect

19. Conclusions
Lepton Flavour Universality Violation (LFUV)
Electron channels: SM-like
b→sµµ >5σ
b→cτν >4σ
aµ >3σ
τ→Kν >2σ
Leptoquarks provide a very promising solution to the flavour anomalies
Andreas Crivellin