1. Explaining the Flavour Anomalies with the Pati-Salam Leptoquark
Andreas Crivellin
PSI (LTP) & UZH
Explaining the Flavour Anomalies with the Pati-Salam Leptoquark
La Thuile,

2. Outline Introduction: Leptoquark and the Flavour anomalies
The Pati-Salam Leptoquark
b→sττ enhancement and loop effects b→sl+l-
Importance of Loop Effects
Possible UV completions
QCD corrections to semileptonic B decays
Conclusions
Andreas Crivellin

3. Hints for New Physics Lepton Flavour Universality Violation (LFUV)
Electron channels: SM-like
b→sµµ >5σ
b→dµµ b→uτν 1-2σ
b→cτν >3σ
aµ >3σ
τ→Kπν >2σ
Andreas Crivellin

4. Leptoquarks are tailor-made to explain the
Leptoquark effects
b→cτν
Tree-level effects in semi-leptonic decays
Loop-suppressed effects in other flavour observables like b→sγ and ΔF=2 processes which agree with the SM predictions.
b→sμμ
Leptoquarks are tailor-made to explain the
flavour anomalies

5. Vector Leptoquark SU(2) Singlet
Left-handed 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

6. Vector LQ Phenomenology
Compatible with constraints for generic couplings

7. very strongly enhanced
R(D(*)) and b→sττ
Large couplings to the second generation
b→sττ
very strongly enhanced
B. Capdevila, AC, S. Descotes-Genon, L. Hofer and J. Matias, PRL

8. Important Loop-Effects
Explanation of b→cτν requires large bτ and sτ couplings (follows from SU(2) invariance)
AC, C. Greub, D. Müller, F. Saturnino, PRL 2018
Large loop effects in b→sμμ

9. Important Loop-Effects
Explanation of b→cτν requires large bτ and sτ couplings (follows from SU(2) invariance)
AC, C. Greub, D. Müller, F. Saturnino, PRL 2018
Large loop effects in b→sμμ

10. Perfect agreement with data
Pati-Salam LQ can explain the flavour anomalies

11. Possible UV completions
SU(4)×SU(3)’×SU(2)L×U(1)Y + Vector-like fermions L. Di Luzio, A. Greljo, M. Nardecchia, arXiv:
SU(4)×U(2)L×SU(2)R + Vector-like fermions L. Calibbi, AC, T. Li, arXiv:
SU(4)× SU(4)× SU(4) M. Bordone, C. Cornella, J. Fuentes-Martin, G. Isidori, arXiv:
SU(4) ×U(2)L×SU(2)R including scalar LQs and light right-handed neutrinos J. Heeck, D. Teresi, arXiv:
SU(8) might even explain ɛ’/ɛ S. Matsuzaki, K. Nishiwaki and K. Yamamoto, arXiv:
SU(4)×U(2)×SU(2)R in RS background M. Blanke, AC, arXiv:
Good solution, but challenging UV completion

12. Pati-Salam RS Phenomenology
M. Blanke, AC, PRL 2018
Modell well motivated + limited but sizable effect

13. QCD corrections to the Matching
Perform matching
Correct for 4-dimensional Fierz identities

14. Slightly weaker LHC constraints
Results
J. Aebischer, AC, C. Greub,
Slightly weaker LHC constraints

15. Conclusions
The Pati-Salam Leptoquark is tailor made to explain the flavour anomalies
Explanation of R(D) and R(D*) requires a generic flavour structure:
Huge enhancement of b→sττ
Sizable loop effects in b→sll and b→sνν
Explaining R(D) and R(D*) with the Pati-Salam leptoquark give the right loop effects in b→sll
QCD corrections to the matching make LHC bounds slightly weaker
Andreas Crivellin

16. Results independent of the LQ representation
Operators generated by vector leptoquark
Operators generated by scalar leptoquark
vector operator
scalar operator
vector operator
scalar operator
tensor operator
Results independent of the LQ representation