Andreas Crivellin New Physics in the Flavour Sector

Andreas Crivellin New Physics in the Flavour Sector

Experimental physicist at dinner on Tuesday: “Talks on theoretical flavour physics are the worst ones” I will try to show that this is a prejudice In view of this goal, I apologize in advance for being too simple, covering only selected topics and models and not having a complete list of references For CP violation in flavor physics see talk of Jernej Kamenik

Outline: n n Introduction to flavor physics Flavour anomalies n n n Possible New Physics Explanations n n n Z’ Extended Higgs sector Leptoquarks Simultaneous Explanations of Anomalies Conclusions

Flavour Physics n n All flavor violation in the SM originates from the charged W-vertex Flavour changes Involve small off-diagonal CKM elements n Flavour changing neutral currents (FCNCs) are absent in the SM at tree-level. n Induced at the 1 -loop level by quantum fluctuations suppressed by the large W mass n FCNCs are n Very suppressed in the SM n Maybe large in theories beyond the SM n Excellent place to search for heavy New Physics

Tree-level determination of the CKM elements n V ub n n n Vcb n n n Vus n Kaon decays

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

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

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

Global CKM Fit Indirect and direct determinations agree very well

B→Xsγ n Inclusive decay n Complete perturbative calculation Misiak et al. 1503. 01789 SM and experiment agree very well Test of chirality changing new physics

b→sll n Semileptonic neutral current decays n Hadronic uncertainties Test different operators than the other FCNCs

Flavour Anomalies

“Missing Energy” Decays 3/9/2021

B→K*µµ n n Semi-leptonic decay form factor dependence Clean observables are (approximately) free of hadronic uncertainties 2 -3 σ deviation from the SM mostly in P 5’

B→K*µµ n n Can be explained by a NP contribution to the operator New physics explanation is not easy (MSSM, 2 HDM do not work). n Most natural explanation: n n ar. Xiv: 1307. 5683 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), 1501. 00367.

R(K) = B→Kµµ/B→Kee n Lepton flavour universality violation n 2. 6 σ deviation from theoretically rather clean SM expectation Also lepton flavour violation?

Global fit to b→sμμ data n Global analysis give a very good fit to data W. Altmannshofer, D. M. Straub, ar. Xiv: 1503. 06199. T. Hurth, F. Mahmoudi, and S. Neshatpour, 1410. 4545. Descotes-Genon et al. 1501. 04239 n Symmetry based solutions give a very good fit to data: n n n Fit is 4 -5 σ better than in the SM

Z’ explanations U. Haisch et al. 1308. 1959 W. Altmannshofer et al. 1403. 1269 A. C. et al. 1501. 00993 …. . More in the talk of Alejandro Celis

Leptoquarks n n n 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

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

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

n 2. 6 σ difference from zero

n Can be explained in the effective field theory approach by R. Harnik, J. Kopp, and J. Zupan, 1209. 1397. G. Blankenburg, J. Ellis, and G. Isidori, 1202. 5704. S. Davidson and P. Verdier, 1211. 1248. n No dominant contribution from vector-like fermions A. Falkowski, D. M. Straub, and A. Vicente, 1312. 5329 Extended Higgs sector J. Heeck et al. 1412. 3671 A. Greljo et al. ar. Xiv: 1502. 07784 A. C. et al. ar. Xiv: 1501. 00993. . .

n Tau decays n Anomalous magnetic moment of the muon deviations in the lepton sector

Models for Simultaneous Explanations of Anomalies

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

2 HDM with gauged Lμ-Lτ

Horizontal charges: LHC limits

Leptoquark Explanations of b→sμμ and B→ D(*)τν n Tree-level contribution to loop effect in n but can explain Anarchic flavor structure n M. Bauer, M. Neubert ar. Xiv: 1511. 01900 n Tree-level contribution to and n Hierarchical flavor structure, large third generations couplings, small first and second ones. 29

Tree-level Leptoquark Explanation Third generation couplings Misalignment between interaction and mass basis L. Calibbi, A. C. and T. Ota, PRL, ar. Xiv: 1506. 02661 30

2 HDM of type X n n See Talk of Eung Jin Chun One Higgs doublet couples only to quarks the other Higgs doublet to leptons. Additional free parameters: Couplings to leptons are tan(β) enhanced 3/9/2021

AC, Julian Heeck, Peter Stoffer. ar. Xiv: 1507. 07567. PRL 2016 3/9/2021 32

Prediction: Branching ratio can even reach the percent level AC, Julian Heeck, Peter Stoffer. ar. Xiv: 1507. 07567. PRL 2016 3/9/2021 33

3/9/2021 34

3/9/2021 35

Branching ratio can even reach the percent level 3/9/2021 36

No simultaneous explanation without fine-tuning 3/9/2021 37

Conclusions Z’ gauge boson Leptoquarks Extended Higgs sector Conclusions