The Lepton Flavor Violation road to New Physics Avelino Vicente - - PowerPoint PPT Presentation

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The Lepton Flavor Violation road to New Physics Avelino Vicente - - PowerPoint PPT Presentation

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The Lepton Flavor Violation road to New Physics Avelino Vicente IFIC CSIC / U. Valencia IMHEP 2019 Bhubaneswar Bhubaneswar Avelino Vicente - The LFV road to New Physics 1 Introduction Before the LHC started operating we all hoped for

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Bhubaneswar Avelino Vicente - The LFV road to New Physics 1

The Lepton Flavor Violation road to New Physics

IMHEP 2019

Bhubaneswar

Avelino Vicente IFIC – CSIC / U. Valencia

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Avelino Vicente - The LFV road to New Physics 2 Bhubaneswar

Introduction

Before the LHC started operating we all hoped for great discoveries...

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LHC e LHC exp xpec ecta tations tions

Supersymmetry Extra d dim imensio ions Co Composit iteness Mic icroscopic ic bla lack hole les

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LH LHC r C resul ults... ..

125 GeV palm tree

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Introduction

Do we have a good reason to go Beyond the Standard Model?

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Avelino Vicente - The LFV road to New Physics 6 Bhubaneswar

Introduction

Do we have a good reason to go Beyond the Standard Model? The lepton sector is still to be understood! Neutrinos!

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Neutrinos and the lepton sector

Dear radiactive Ladies and Gentlemen... 1930 Pauli's neutrino hypothesis December 4th, 1930 Letter to his colleagues in Tübingen

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Avelino Vicente - The LFV road to New Physics 8 Bhubaneswar

Open questions

What is the origin of neutrinos masses? Are they Dirac or Majorana? What is the absolute scale of neutrino masses? What is the mass ordering? Are there more than three neutrinos? Maybe sterile? Is there CP violation in the lepton sector?

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Avelino Vicente - The LFV road to New Physics 9 Bhubaneswar

Lepton fmavor violation

In the Standard Model, three copies of the leptonic SU(2) doublet are introduced

Gauge and Yukawa interactions

Is lepton flavor a conserved quantity?

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Avelino Vicente - The LFV road to New Physics 10 Bhubaneswar

Neutrino oscillations: LFV

We already know the answer: NO

Neutrino flavor oscillations: flavor violating process!

Then... is this process a sign of BSM physics?

Yes it is!

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What about cLFV?

In conclusion, lepton flavor is not conserved: there is lepton flavor violation (LFV) However... what about charged lepton flavor violation (cLFV)? Never observed... ...

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What about cLFV?

SM + Dirac neutrino masses

Since neutrino masses are the only source of LFV, all cLFV amplitudes are strongly suppressed (in fact, GIM suppressed)

: lepton mixing matrix

[analog of the CKM matrix in the lepton sector]

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Why do we care about LFV?

The observation of cLFV would be a clear signal of (non-trivial) physics beyond the Standard Model In fact, most BSM models predict large cLFV rates We can probe very high energy scales!

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Why do we care about LFV?

Example 1: Supersymmetric models

Sleptons: a whole new sector coupled to the SM leptons Strong constraints on the off-diagonal soft terms

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Avelino Vicente - The LFV road to New Physics 15 Bhubaneswar

Why do we care about LFV?

Example 2: Babu-Zee model

Small off-diagonal h couplings and/or heavy k's are required

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Avelino Vicente - The LFV road to New Physics 16 Bhubaneswar

Experimental projects

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Avelino Vicente - The LFV road to New Physics 17 Bhubaneswar

Experimental projects

Figure taken from Bernstein & Cooper [arXiv:1307.5787]

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Experimental projects

MEG MEG Mu3e Mu3e LHC LHC Mu2e Mu2e 2e DeeMe Dee eeMe COMET COMET PRISM/PRIME PRISM/PRIME Belle-II Bel elle- e-II

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LFV : Where to look for?

conversion in nuclei LFV at colliders

BSM

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LFV : Where to look for?

Everywhere!

Table taken from Buras et al [arXiv:1006.5356]

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What contribution dominates ?

In many models of interest: Photonic dipole contributions

Most popular example: MSSM

vs

[Hisano et al 1996; Arganda, Herrero 2006] Dipole dominance

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The LFV program

  • Search for LFV in as many observables as possible: they

might have information about different sectors of the theory

  • Study the relations among different observables (ratios,

correlations, hierarchies...)

  • Understand the origin of such relations: what is the

underlying physics?

In order to unravel the physics behind LFV (and perhaps neutrino masses!) we must:

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Outline of the talk

  • Introduction: Lepton Flavor Violation
  • Selected topics
  • Final remarks
  • LFV in low-scale seesaw models
  • LFV in B-meson decays
  • Master Majorana parametrization
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LFV in low-scale seesaw models

Chuck Norris fact of the day Chuck Norris counted to

  • infinity. Twice.

With Asmaa Abada, Manuel E. Krauss, Werner Porod, Florian Staub and Cédric Weiland

PRD 90 (2014) 013008 [arXiv:1312.5318] JHEP 1411 (2014) 048 [arXiv:1408.0138]

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Low-scale seesaw models

[Mohapatra, Valle, 1986]

The Inverse Seesaw

singlet states: 9x9 mass matrix

[if ]

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Standard vs Inverse Seesaw

Standard Seesaw

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Standard vs Inverse Seesaw

Inverse Seesaw

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Penguins in the inverse seesaw

[Ilakovac, Pilaftsis, 1995; Deppisch, Valle, 2005]

The GIM suppression is spoiled by the singlet neutrinos

Much larger rates expected!

Rectangular matrix

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Boxes in the inverse seesaw

  • Non-supersymmetric contribution
  • Relevant for light singlet neutrinos
  • Large non-dipole contributions

Furthermore, for conversion in nuclei and ...

[Ilakovac, Pilaftsis, 2009; Dinh, Ibarra, Molinaro, Petcov, 2012; Alonso, Dhen, Gavela, Hambye, 2013; Ilakovac, Pilaftsis, Popov, 2012]

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Low-scale seesaw models

[Abada, Krauss, Porod, Staub, AV, Weiland, 2014] 75 pages paper First complete study of all SUSY and non-SUSY contributions!

  • Analytical and numerical study of
  • All contributions included
  • A few hundred Feynman diagrams

conversion in nuclei

How were they computed? Later...

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Low-scale seesaw models

The anatomy of LFV strongly depends on and

4

Excluded

[Abada, Krauss, Porod, Staub, AV, Weiland, 2014]

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FlavorKit

Manual: arXiv:1405.1434 Website: http://sarah.hepforge.org/FlavorKit.html [Porod, Staub, AV, 2014] Many observables ready to be computed in your favourite model! Easily extendable Not limited to a single model: use it for the model of your choice

A computer tool that provides automatized analytical and numerical computation

  • f flavor observables. It is based on SARAH, SPheno and FeynArts/FormCalc.
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LFV in B-meson decays

With Sofiane M. Boucenna, Paulina Rocha-Morán and José W. F. Valle

PLB 750 (2015) 367 [arXiv:1503.07099] arXiv:1810.02135

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The anomalies

Episode IV: A new hope

2013 : First anomalies found by LHCb

Episode V: LHCb strikes back

2014 : Lepton universality violation

Episode VI: Return of the anomalies

2015 : LHCb confirms first anomalies

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P5’ anomaly confirmed + little LFVU indication

Episode I: The Belle menace

2016 : Belle finds additional hints

Episode II: Attack of RK*

2017 : More universality violation in LHCb

low bin central bin

[ No new episode in 2018 though.... ]

The anomalies

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Beyond the Standard Model

The anomalies

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Boring Sizable corrections

The anomalies

(+ fluctuations)

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LFV in B meson decays

What about LFV?

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[Glashow et al, 2014]

Lepton universality violation generically implies lepton flavor violation

Gauge basis Mass basis

LFV in B meson decays

What about LFV?

However: we must have a flavor theory in order to make predictions

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[Boucenna, Valle, AV, 2015]

What if ?

Neutrino oscillations Neutrinos B-physics

Working hypothesis:

Are the LHCb anomalies related to neutrino

  • scillations?

Lines: BF Bands:

Non-trivial link!

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An explicit model

[Rocha-Moran, AV, 2018] Extension of [Aristizabal Sierra, Staub, AV, 2015]

Gauge symmetry boson breaking: Vector-like

Vector-like = “joker” for model builders

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Similar to Altmannshofer et al, Crivellin et al, 2014 [Aristizabal Sierra, Staub, AV, 2015] Z’ couplings induced by mixing with vector-like fermions

Solving the anomalies

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[Rocha-Morán, AV, 2018]

Neutrino mass generation

Inverse seeesaw-like mechanism

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LFV phenomenology

Correlation is (almost)* unavoidable

* : could be broken by loops (indeed possible!)

[Rocha-Morán, AV, 2018]

Anomaly Bs-mixing

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Master Majorana parametrization

With Isabel Cordero-Carrión and Martin Hirsch

arXiv:1812.03896

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Motivation

FAKE CORRELATIONS!! FAKE CORRELATIONS!!

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The master formula

: symmetric Majorana neutrino mass matrix : global factor [numerical factors, model parameters, mass ratios, ...] : Yukawa matrix : matrix [dimensions of mass] : Yukawa matrix [ ] All Majorana neutrino mass models!

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T

  • wards a master parametrization

Goal: Goal:

Neutrino oscillation experiments Model parameters Casas-Ibarra parametrization [ Casas, Ibarra, 2001 ]

To establish a general, complete and programmable parametrization

  • f the and Yukawa matrices

Particular case: Type-I seesaw

Master parametrization

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The master parametrization

Experimental input: Model input: Free Yukawa parameters: Summary: n-data

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The master parametrization

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BNT model

[ Babu, Nandi, Tavartkiladze, 2009 ] An example of

Lepton number violation

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BNT model

[ Babu, Nandi, Tavartkiladze, 2009 ]

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Black: Trivial scan Purple: General scan

[ & ]

Model in SARAH and scans with SSP [Staub] BR computed with FlavorKit [Porod, Staub, AV] A large parameter space that can only be covered with the master parametrization n-data NH within 3 n-data NH BFP

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Final remarks

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Final remarks

LFV is going to live a golden age Many LFV observables. Correlations are not only possible, but in fact expected! We must be ready: understand the LFV anatomy, patterns, correlations, hierarchies...

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Thank you!

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Backup slides

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Low-scale seesaw models

[Abada, Krauss, Porod, Staub, AV, Weiland, 2014]

Excluded

4

The anatomy of LFV strongly depends on and

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Low-scale seesaw models

The dipole dominance is broken for low RH neutrino masses

[Abada, Krauss, Porod, Staub, AV, Weiland, 2014]

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Low-scale seesaw models

T au LFV decay ratios provide information on the mass scales

Excluded [Abada, Krauss, Porod, Staub, AV, Weiland, 2014]

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Interpreting the anomalies

Effective hamiltonian

[ analogous for primed operators ]

: Wilson coefficients : Operators

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Optimized observables

[Descotes-Genon et al, 2012, 2013]

differential angular distribution

[Figure borrowed from Javier Virto]

The anomalies

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LFV at LHCb

Lepton flavor violating decays at

(at 90% CL) Large production of 's, clean final state To be compared with (Belle)

[Aaij et al, LHCb collaboration, 2014]

Limits improved with respect to CDF

Impressive result in a hadronic machine [Aaij et al, LHCb collaboration, 2013]

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T ype-I seesaw

everyone’s model [ Minkowski, 1977 ]

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Inverse seesaw

[ Mohapatra, Valle, 1986 ]

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Scotogenic model

[ Ma, 2006 ]

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The master parametrization

unitary matrix Leptonic mixing matrix

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The master parametrization

Singular-value decomposition Unitary matrices

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The master parametrization

Arbitrary matrices [ Note: absent if ]

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The master parametrization

unitary matrix

Absent if

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The master parametrization

Invertible upper triangular matrix Numerical matrix whose form depends on

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The master parametrization

Absent if

antisymmetric

Matrix whose form depends on

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The master parametrization

For :

[ Different matrix forms for other values of . Ask me if you want to see them ]

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The Casas-Ibarra limit

Casas-Ibarra parametrization [Casas, Ibarra, 2001] Particular case: Type-I seesaw , and are absent

  • rthogonal