Search for in muonic atom at COMET experiment

Masato Yamanaka (ICRR, Univ. of Tokyo)

Collaborators

Masafumi Koike (Saitama Univ.)Yoshitaka Kuno (Osaka Univ.)Joe Sato (Saitama Univ. )

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Introduction

Introduction

In Standard Model (SM)

Lepton Flavour Violation (LFV) through the neutrino oscillation

But … Forever invisible

Discovery of the LFV signalOne of the evidence for beyond

the SM

Introduction

Prove for structure of new physics

Comparing LFV signals in each process type Discrimination of new physics

models

Desire for detectable new LFV process

Supersymetric model

Extra dimension model

Introduction

New idea for LFV search in muonic

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What is sensitive to ?

Flavor violation between and e

m

Where is the stage ?

MUSIC, COMET, and PRISM

What is advantage ?

Clean signal, and simultaneous search with other LFV processes

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nucleus muon electron

Muonic atom

electron 1S orbitmuon 1S

orbit

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in muonic atom

electron 1S orbitmuon 1S

orbit

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LFV vertex

Interaction rate

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electron 1S orbitmuon 1S

orbit

Interaction rate

Cross section for elemental interaction

in muonic atom

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LFV vertex

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Lagrangian

LFV source

Model dependent parmeters

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Lagrangian

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Lagrangian

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For A g (i = 1, 2, …, 6)

L(R) =～ i

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electron 1S orbitmuon 1S

orbit

Interaction rate

Overlap of wave function of and

m e

in muonic atom

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LFV vertex

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Muonic atom

Overlap of wave functions ∴Muon localizing

at nucleus positon

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Branching ratio

Lifetime of free muon (2.197 10 s)

-6×

Lifetime of bound muon

2.19 10 s for H

-6× 1

(7 - 8) 10 s for U

-8×238

Discovery reach

Discovery reach

Branching ratio ( )

m e g

Ratio between BR( ) and BR( )

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Discovery reach

Ratio between BR( ) and BR( )

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Discovery reach

Discovery reach

For run-time 1 year 3 10 s

× 7～

10

18

10

19

- muon at COMET experiment

Discovery reach

can be first signal of LFV !?

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Summary

Summary

New LFV process

in muonic atom

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Clean signal (back to back electron with E m /2)

Interaction rate

Advantage : Large nucleus

～=e m

Detectable in on-going or future experiments

We wish to observe LFV in the process

Appendix

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nucleus muon electron

Muonic atomelectron 1S orbit

muon 1S orbit

One of the candidates for beyond the SM Supersymmetric (SUSY)

modelSupersymmetry

Lepton SleptonGauge boson

Gaugino

Symmetry between boson and fermion

Stability of Higgs mass, dark matter, gauge coupling unification, hierarchy problem, and so on

Why SUSY models ??