Higgs mediated lepton flavour violation. Alejandro Celis

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1 Higgs mediated lepton flavour violation Alejandro Celis ( ) IFIC, Universitat de Valencia-CSIC XLII International Meeting on Fundamental Pysics Benasque, Spain

2 Contents Motivation to study Higgs mediated LFV Low energy constraints Recent progress on decays Improving te Hadron Pysics of Non-Standard-Model Decays: Example Bounds on R-parity Violation J. T. Daub et al. ( ) Lepton flavor violation in te Higgs sector and te role of adronic tau-lepton decays AC, Cirigliano, Passemar ( ) Prospects for LFV Higgs decays at te LHC A. Celis. ( ) Higgs mediated LFV

3 Te Higgs boson couplings are not dictated by gauge symmetries. Diagonalizing te mass terms after EWSB Neutral weak current is diagonal in te fermion mass basis. Carged weak current is non-diagonal in te fermion mass basis CKM matrix A. Celis. ( ) Higgs mediated LFV

4 In te absence of Yukawa couplings te SM as a global flavour symmetry rotations of Te lepton sector posses a similar flavour symmetry, but in tis case it depends on ow neutrino masses are implemented rotations of Minimal field content Cirigliano et al. ( ) Wit te discovery of te 126 GeV Higgs boson, we can now access directly te flavour symmetry breaking sources (Yukawa couplings) A. Celis. ( ) Higgs mediated LFV

5 Flavour violation in te Higgs sector Many scenarios of pysics beyond te SM predict rates for carged lepton flavour violating transitions at observable levels for a long review see: M. Raidal et al. ( ) Different cannels to probe carged LFV at low energy Important to unravel te origin of LFV conversion in nuclei A. Celis. ( ) Higgs mediated LFV

6 Flavour violation in te Higgs sector So far, wat do we now about te Yukawa couplings of te 126 GeV Higgs? LHC data confirms tat te relation old for 3º family fermions Ellis, You ( ) (wit still significant uncertainties) Coupling wit vector bosons also SM-like Not muc can be done for 1º and 2º family fermions at te LHC. Hig Lum. LHC can probably measure A. Celis. ( ) Higgs mediated LFV

7 Flavour violation in te Higgs sector Indirect bonds on flavour canging couplings of te 126 GeV Higgs are already quite strong in most of te cases, putting te relevant decay rates beyond te reac of colliders In te quark sector Blankenburg, Ellis, Isidori ( ) Harnik, Kopp, Zupan ( ) b bd P L + Y db P R d c ctp L + Y tc P R Y t Ybd d P L + Y db P R b M. Bona et al. (a)( ) Isidori, Nir, Perez ( ) ū tup L + Y ut P R (b) Y flavour canging Higgs couplings wit top are weakly constrained from CMS multi-lepton searc Harnik, Kopp, Zupan ( ) A. Celis. ( ) Higgs mediated LFV

8 Flavour violation in te Higgs sector In te lepton sector YP L + Y P R + P L + Y P R P L + Y P R P L + Y P R + P L + Y P R P L + Y P R P L + Y P R e P L + Y e P R e P L + Y P R e P L + Y e P R e e e P L + Y e P R ee P L + Y ee P R e e + + N N N N N N conversion in nuclei Indirect bounds are very weak for tau-mu and tau-e fixing te diagonal couplings to teir SM value Harnik, Kopp, Zupan ( ) Blankenburg, Ellis, Isidori ( ) Diaz-Cruz, Toscano ( ) A. Celis. ( ) Higgs mediated LFV

9 LFV radiative decays A transition dipole moment is generated at te loop level Dominant contribution from 2-loop diagrams of Barr-Zee type Cang, Hou, Keung (1993) P L + Y P R + P L + Y P R P L + Y P R P L + Y P R,Z,Z 1-loop diagram involve t t W W tree cirality flips Tis is just an accident at te 1-loop level and can be avoided W,Z W Z at iger orders Bjorken, Weinberg (1977) diagrams extracted from Harnik, Kopp, Zupan (2012)

10 LFV leptonic decays If LFV leptonic decays are observed at some point, a Dalitz plot analysis would provide a useful andle to disentangle different kinds of new pysics suppressed by small Yukawa subdominant Dassinger, Feldmann, Mannel, Turczyk ( ) YP L + Y P R + P L + Y P R P L + Y P R additional suppression in te decay rate compared wit te radiative mode diagrams extracted from Harnik, Kopp, Zupan (2012)

11 mu-e conversion in nuclei Cirigliano, Kitano, Okada, Tuzon ( ) By comparing different target nuclei Kitano, Koike, Okada ( ) one can disentangle different effective operators Kuno, Okada, ( ) e P L + Y e P R e e e e e P L + Y P R e P L + Y e P R e P L + Y e P R ee P L + Y ee P R + + N N N N N N plots from Harnik, Kopp, Zupan (2012) only Higgs coupling to up and down quarks relevant? Were does te nucleon mass comes from? A. Celis. ( ) Higgs mediated LFV

12 mu-e conversion in nuclei Q=c,b,t trace of te energy-momentum tensor (at zero momentum transfer) from triangle anomaly

13 A long-standing problem, ow large is te strange quark content in te nucleon? from a recent review wit state of te art Lattice calculations R. D. Young,

14 Recent progress on decays Important points: - Need to consider te Higgs coupling wit strange quarks and te effective Higgs-gluon interaction induced by eavy quarks - Need a proper description of te adronic matrix elements up to invariant masses of te pion pair of ~1GeV J. T. Daub et al. ( ) Tese two points were not being addressed in te literature!! First consideration of tese points for Higgs mediated decays AC, Cirigliano, Passemar ( ) Interestingly, te problem was solved years ago in te context of very ligt Higgs decays Donogue, Gasser, Leutwyler (1990)

15 Poton mediated contributions require te pion vector form factor Teoretically: decay very well described by resonances 10 Fit result Belle data Dispersive parametrization following te properties of analyticity and unitarity of te FF F V (s) 2 1 Determined from a fit to te Belle data 0.1 Guerrero, Pic 98, Pic, Portolés 08, Gomez, Roig s [GeV 2 ] AC, Cirigliano, Passemar ( )

16 Te oter adronic matrix elements were determined in previous works about Using leading-order ciral perturbation teory extracted from Donogue, Gasser, Leutwyler (1990) Volosin (1985) Using te triple constraints of ciral symmetry, analyticity, and unitarity, togeter wit exp. input pi-pi scattering, etc very far from te naive expectation Volosin (1985)

17 Previous studies ave been considering only (LO-CPT) Equivalent to te naive estimate Impact of adronic matrix elements on AC, Cirigliano, Passemar ( )

18 LHC would provide stronger constraints, even wit present data Harnik, Kopp, Zupan ( ) Davidson, Verdier ( ) Estimated sensitivity of te LHC wit 20 fb^- of data Davidson, Verdier ( )

19 PDG 201X (126) properties Decay Modes Confidence Level...

20 Summary of main points discussed Higgs interaction wit nucleons and were does te nucleon mass comes from? Recent progress on decays J. T. Daub et al. ( ) AC, Cirigliano, Passemar ( ) rely on tecniques developed for te problem of calculating te decay widt of a ~1 GeV Higgs into two pions, ot topic back in te late 80 s and 90 s Direct searc for decays at te LHC can probe flavour violating Higgs couplings beyond te limits set by LFV tau decays

21 Ricard Tompson Back-up

22 LFV semileptonic tau decays Precise knowledge of adronic states involved provides important information (neglecting Z penguins) even odd Possible to isolate CP-even and CP-odd Higgs excange in semileptonic decays

23 From S. Miara

24 following DGL

25 Higgs to two pions proceeds mostly troug te Higgs-gluon coupling and te Higgs-strange quark coupling. but pions ave u,d valence quarks? Violation of te OZI rule (Okubo-Zweig-Iizuka)