Higgs mediated lepton flavour violation Alejandro Celis

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Higgs mediated lepton flavour violation

IFIC, Universitat de Valencia-CSIC

29-02-2014

Alejandro Celis

_(e-mail)

XLII International Meeting on Fundamental Physics Benasque, Spain

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A. Celis. (29-02-2014)

Motivation to study Higgs mediated LFV

Low energy constraints

Recent progress on decays

AC, Cirigliano, Passemar (1309.3564)

J. T. Daub et al. (1212.4408)

Higgs mediated LFV

Prospects for LFV Higgs decays at the LHC

Improving the Hadron Physics of Non-Standard-Model Decays: Example Bounds on R-parity Violation

Lepton flavor violation in the Higgs sector and the role of hadronic tau-lepton decays

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Charged weak current is non-diagonal in the fermion mass basis Neutral weak current is diagonal in the fermion mass basis.

CKM matrix Diagonalizing the mass terms after EWSB

The Higgs boson couplings are not dictated by gauge symmetries.

A. Celis. (29-02-2014) Higgs mediated LFV

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In the absence of Yukawa couplings the SM has a global flavour symmetry

rotations of

The lepton sector posses a similar flavour symmetry, but in this case it depends on how neutrino masses are implemented

rotations of

Minimal field content

Cirigliano et al. (0507001)

With the discovery of the 126 GeV Higgs boson, we can now access directly the flavour symmetry breaking sources (Yukawa couplings)

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Many scenarios of physics beyond the SM predict rates for charged lepton flavour violating transitions at observable levels

for a long review see: M. Raidal et al. (0801.1826)

Different channels to probe charged LFV at low energy

Important to unravel the origin of LFV conversion in nuclei

Flavour violation in the Higgs sector

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So far, what do we now about the Yukawa couplings of the 126 GeV Higgs?

LHC data confirms that the relation hold for 3º family fermions

(with still significant uncertainties) Ellis, You (1303.3879)

Not much can be done for 1º and 2º family fermions at the LHC.

High Lum. LHC can probably measure

Flavour violation in the Higgs sector

Coupling with vector bosons also SM-like

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Indirect bonds on flavour changing couplings of the 126 GeV Higgs are already

quite strong in most of the cases, putting the relevant decay rates beyond the reach of colliders

In the quark sector

h

d¯ b

¯b d

Y^∗

bdP_L+Y_dbP_R

Y^∗

bdP_L+Y_dbP_R

t

h

t

¯ u c

¯ c u

Y^∗

ctP_L+Y_tcP_R

Y_tu^∗P_L+Y_utP_R Y_ct^∗P_L+Y_tcP_R Y^∗

tuP_L+Y_utP_R

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Flavour violation in the Higgs sector

Isidori, Nir, Perez (1002.0900) M. Bona et al. (0707.0636)

Harnik, Kopp, Zupan (1209.1397)

Blankenburg, Ellis, Isidori (1202.5704)

Harnik, Kopp, Zupan (1209.1397) from CMS multi-lepton search

flavour changing Higgs couplings with top are weakly constrained

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Flavour violation in the Higgs sector

fixing the diagonal couplings to their SM value

In the lepton sector

Blankenburg, Ellis, Isidori (1202.5704) Harnik, Kopp, Zupan (1209.1397)

τ h

µ µ µ

Y_{τ µ}^∗PL+YµτPR

Y_µµ^∗PL+YµµPR

+ τ γ

µ µ µ

Y_µµ^∗PL+YµµPR

h

N µ

N

Y_µe^∗PL+YeµPR e

+

µ h

µ

γ

N µ

N e

Y_µµ^∗PL+YµµPR Y_µe^∗PL+YeµPR

+

e h

e

γ

N µ

N e

Y_µe^∗PL+YeµPR Y_ee^∗PL+YeePR

τ h

τ τ

γ

µ

Y_{τ τ}^∗PL+Yτ τPR Y_{τ µ}^∗PL+YµτPR

+ µ

h

τ µ

γ

µ

Y_{τ µ}^∗PL+YµτPR Y_µµ^∗PL+YµµPR

Diaz-Cruz, Toscano (9910233)

Indirect bounds are very weak for tau-mu and tau-e

conversion in nuclei

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µ

h γ, Z

t t

τ

γ

µ µ

h γ, Z

W W

τ

γ

µ

h γ, Z

W W

τ

γ µ

µ h

µ Z

µ τ

γ µ

diagrams extracted from Harnik, Kopp, Zupan (2012)

LFV radiative decays

A transition dipole moment is generated at the loop level

Dominant contribution from 2-loop diagrams of Barr-Zee type

Chang, Hou, Keung (1993)

1-loop diagram involve three chirality flips

This is just an accident at the 1-loop level and can be avoided at higher orders

Bjorken, Weinberg (1977)

τ h

τ τ

γ

µ

Y_{τ τ}^∗PL+Yτ τPR Y_{τ µ}^∗PL+YµτPR

+ µ

h

τ µ

γ

µ

Y_{τ µ}^∗PL+YµτPR Y_µµ^∗PL+YµµPR

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LFV leptonic decays

τ h

µ

µ µ

Y_{τ µ}^∗ P_L + Y_µτP_R

Y_µµ^∗ P_L + Y_µµP_R

+ τ γ

µ

µ µ

Y_µµ^∗ P_L +Y_µµP_R

diagrams extracted from Harnik, Kopp, Zupan (2012)

subdominant

suppressed by small Yukawa

additional suppression in the decay rate compared with the radiative mode

Dassinger, Feldmann, Mannel, Turczyk (0707.0988)

If LFV leptonic decays are observed at some point, a Dalitz plot analysis would provide a useful handle to disentangle different kinds of new physics

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mu-e conversion in nuclei

h

N µ

N

Y_µe^∗P_L+Y_eµP_R e

+

µ h

µ

γ

N µ

N e

Y_µµ^∗ P_L+Y_µµP_R Y_µe^∗P_L+Y_eµP_R

+

e h

e

γ

N µ

N e

Y_µe^∗P_L+Y_eµP_R Y_ee^∗P_L+Y_eeP_R

plots from Harnik, Kopp, Zupan (2012)

only Higgs coupling to up and down quarks relevant?

Where does the nucleon mass comes from?

By comparing different target nuclei

one can disentangle different effective operators Kuno, Okada, (9909265)

Kitano, Koike, Okada (0203110) Cirigliano, Kitano, Okada, Tuzon (0904.0957)

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mu-e conversion in nuclei

(at zero momentum transfer)

Q=c,b,t

from triangle anomaly

trace of the energy-momentum tensor

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A long-standing problem, how large is the strange quark content in the nucleon?

R. D. Young, 1301.1765 from a recent review with state of the art Lattice calculations

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Important points:

- Need to consider the Higgs coupling with strange quarks and the effective Higgs-gluon interaction induced by heavy quarks

- Need a proper description of the hadronic matrix elements up to invariant masses of the pion pair of ~1GeV

These two points were not being addressed in the literature !!

First consideration of these points for Higgs mediated decays

Interestingly, the problem was solved years ago in the context of very light Higgs decays

Donoghue, Gasser, Leutwyler (1990)

Recent progress on decays

J. T. Daub et al. (1212.4408)

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0 0.5 1 1.5 2 2.5 3

s [GeV²]

0.01 0.1 1 10

|F V(s)|2

Fit result Belle data

Photon mediated contributions require the pion vector form factor

AC, Cirigliano, Passemar (1309.3564) Guerrero, Pich ´98,

Pich, Portolés ´08, Gomez, Roig ´13.

Dispersive parametrization

following the properties of analyticity and unitarity of the FF

Determined from a fit to the Belle data

Theoretically: decay very well described by resonances

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extracted from Donoghue, Gasser, Leutwyler (1990)

Voloshin (1985) Using leading-order chiral perturbation theory

very far from the naive expectation

Using the triple constraints of chiral symmetry, analyticity, and unitarity, together with

exp. input pi-pi scattering, etc

Voloshin (1985)

The other hadronic matrix elements were determined in previous works about

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Previous studies have been considering only

(LO-ChPT)

Equivalent to the naive estimate

Impact of hadronic matrix elements on

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Davidson, Verdier (1211.1248)

LHC would provide stronger constraints, even with present data

Harnik, Kopp, Zupan (1209.1397)

Estimated sensitivity of the LHC with 20 fb^- of data

Davidson, Verdier (1211.1248)

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PDG 201X

h(126) properties Decay Modes

...

Confidence

Level

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Recent progress on decays

AC, Cirigliano, Passemar (1309.3564) J. T. Daub et al. (1212.4408)

Summary of main points discussed

rely on techniques developed for the problem of

calculating the decay width of a ~1 GeV Higgs into two pions, hot topic back in the late 80´s and 90´s Direct search for decays

at the LHC can probe flavour violating Higgs

couplings beyond the limits set by LFV tau decays

Higgs interaction with nucleons and where does the

nucleon mass comes from?

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Richard Thompson

Back-up

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Possible to isolate CP-even and CP-odd Higgs exchange in semileptonic decays

LFV semileptonic tau decays

---

even odd Precise knowledge of hadronic states involved provides

important information

(neglecting Z penguins)

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From S. Mihara

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following DGL

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(Okubo-Zweig-Iizuka) Violation of the OZI rule

Higgs to two pions proceeds mostly through the Higgs-gluon coupling and the Higgs-strange quark coupling.

but pions have u,d valence quarks ¿?

Higgs mediated lepton flavour violation Alejandro Celis