Shinya KANEMURA 1 Search for Lepton Flavor Violation at the ILC Shinya Kanemura (Osaka Univ.) 8th...

Shinya KANEMURA Shinya KANEMURA 11

Search for Lepton Flavor Violation Search for Lepton Flavor Violation at the ILCat the ILC

Shinya Kanemura Shinya Kanemura (Osaka Univ.)(Osaka Univ.)

8th ACFA LC Workshop8th ACFA LC Workshop ＠＠ Taegue, Korea, July 11-14. 2005Taegue, Korea, July 11-14. 2005

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Shinya KANEMURA Shinya KANEMURA

ContentsContents

IntroductionIntroduction Lepton Flavor Violation (LFV)Lepton Flavor Violation (LFV) LFV in SUSY LFV in SUSY Gauge boson mediation & Higgs boson mediation Gauge boson mediation & Higgs boson mediation

LFV search at a LCLFV search at a LC LFV inLFV in LFV in LFV in LFV in Higgs decaysLFV in Higgs decays LFV DIS process LFV DIS process

(a fixed target experiment at a LC) (a fixed target experiment at a LC)

SummarySummary

S.K., T. Ota, K. Tsumura (THDM)

S.K., Y. Kuno, M. Kuze, T. Ota

S.K., K. Matsuda, T. Ota, K.Tsumura,T.Shindou, E. Takasugi (MSSM)

M. Cannoni, St. Kolb, O. Penella 2003

N. Krasnikov 1996,N. Arkani-Hamed et al. 1996M. Hirouchi, M Tanaka 1998J. Hisano et al. 1999M. Guchait, J. Kalinowski, P. Roy 2002

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IntroductionIntroduction

LFV is a clear signal for physics beyond the SM.LFV is a clear signal for physics beyond the SM.

Neutrino oscillation may indicate the possibility of LFV iNeutrino oscillation may indicate the possibility of LFV in the charged lepton sector.n the charged lepton sector.

In many new physics models, LFV can naturally appear.In many new physics models, LFV can naturally appear. SUSY (slepton mixing) SUSY (slepton mixing) Borzumati, MasieroBorzumati, Masiero

Hisano, Moroi, Tobe, YamaguchiHisano, Moroi, Tobe, Yamaguchi Zee model for the ν mass Zee model for the ν mass ZeeZee Models of dynamical flavor violation Models of dynamical flavor violation Hill et al.Hill et al.

Little Higgs models Little Higgs models

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TTau-associated LFV processes may be interestau-associated LFV processes may be interesting at a collider experimenting at a collider experiment

ττ⇔e ⇔e 　　 & & ττ ⇔μ ⇔μ It is less constrained by current data as compared to theμIt is less constrained by current data as compared to theμ

⇔e mixing⇔e mixing

The Higgs mediated LFV is proportional to the Yukawa cThe Higgs mediated LFV is proportional to the Yukawa coupling ⇒oupling ⇒ Tau-associated LFV processesTau-associated LFV processes..

Different behavior from μe mixing case. Different behavior from μe mixing case.

μ→eγ 1.2 ×10 ＾（－ 11 ）　　　　　　　

μ→ ３ e 　　　　　　　　　　 1.1 　 ×10＾（－ 12 ）

μTi→eTi 　　　　　　　　 6.1 ×10 ＾（－ 13 ）

τ→μγ 3.1 ×10 ＾（－ 7 ）τ→ ３ μ 1.4-3.1 ×10 ＾（－

7 ）τ→μη 　　　　　　　　　 3.4 ×10 ＾

（－ 7 ）　

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LFV in SUSYLFV in SUSYSlepton mixing induces LFV at loop.Slepton mixing induces LFV at loop.

Gauge boson mediation

Higgs boson mediation

Form factors: A1L,R

ij, A2L,R

ij , …

Form factors: κij

Kitano, Koike Okada

Babu, KoldaDedes, Ellis, Raidal

Bortzmati, MasieroHisano, Moroi, Tobe, Yamaguchi

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Experimental bounds on LFV parametersExperimental bounds on LFV parameters

For κ31,　 similar bound is obtained.

The strongest bound on κThe strongest bound on κ3232 　　 comes from comes from the τ→μη, τ→3μ results. the τ→μη, τ→3μ results.

The strongest bound on (AThe strongest bound on (A22L,RL,R))ijij comes from comes from

the μ→eγ,τ→eγ,τ→μγ results. the μ→eγ,τ→eγ,τ→μγ results.

Gauge boson mediation

Higgs boson mediation

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A source of slepton mixingA source of slepton mixingin the MSSM+RNin the MSSM+RN

Slepton mixing induces both the Higgs mediated LFV Slepton mixing induces both the Higgs mediated LFV and the gauge mediation. and the gauge mediation.

The off-diagonal elements in the slepton mass matrix The off-diagonal elements in the slepton mass matrix can be induced at low energies, even when it is diagocan be induced at low energies, even when it is diagonal at the GUT scale.nal at the GUT scale.

RGERGE 　　

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Decoupling property of LFVDecoupling property of LFV

Gauge boson mediation :Gauge boson mediation :

Higgs boson mediation : Higgs boson mediation : LFVLFV Yukawa couplingYukawa coupling

NOT always decouple in the large MNOT always decouple in the large MSUSYSUSY limit limit

Decouple in the large MDecouple in the large MSUSYSUSY limit limit

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Why no LFV found ?Why no LFV found ?

It is known that sizable LFV can be induced at loop due tIt is known that sizable LFV can be induced at loop due to slepton mixing. o slepton mixing.

Up to now, however, no LFV evidence has been observeUp to now, however, no LFV evidence has been observed at experiments. d at experiments. μ→e γ, μ→eee, ….μ→e γ, μ→eee, ….

Why? Maybe large MWhy? Maybe large MSUSYSUSY, so that the SUSY effects (in, so that the SUSY effects (including LFV phenomena) decouple?cluding LFV phenomena) decouple?

Even in such a case, we may be able to search LFV Even in such a case, we may be able to search LFV via the Higgs boson mediation, which does not via the Higgs boson mediation, which does not necessarily decouple for a large Mnecessarily decouple for a large MSUSY SUSY limit.limit.

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The correlation between the gauge boson The correlation between the gauge boson mediation and the Higgs mediationmediation and the Higgs mediation

For relatively low mFor relatively low mSUSYSUSY, , the Higgs mediated LFVthe Higgs mediated LFVis constrained by current data for the gauge mediated LFV.is constrained by current data for the gauge mediated LFV.

For mFor mSUSYSUSY > > 　　 O(1)TeV, the gauge mediation becomes O(1)TeV, the gauge mediation becomes suppressed, while the Higgs mediated LFV can be substantial. suppressed, while the Higgs mediated LFV can be substantial.

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Search for LFV at the ILCSearch for LFV at the ILC

LFV in electron-positron (electron) collisionLFV in electron-positron (electron) collision

Direct LFV Yukawa determination via the Higgs boson decaysDirect LFV Yukawa determination via the Higgs boson decays

LFV in a deep inelastic scattering process at a fixed target expLFV in a deep inelastic scattering process at a fixed target experiment eriment

S.K., T. Ota, K. Tsumura (THDM) 2005

LC Search: S.K., K. Matsuda, T. Ota, K.Tsumura,T. Shindou, E. Takasugi (MSSM) 2004

S.K., Y. Kuno, M. Kuze, T. Ota 2004

LHC search: Assamagan et al. (THDM) 2002

S.K., Y. Kuno, M. Kuze, T. Ota, T. Takai

A. Brignole, A. Rossi (MSSM) 2003

K.Arganda., A. Curiel, M.Herrero, D. Temes, 2004

M. Sher, I. Turan (muon beam) 2003


N. Krasnikov 1996,N. Arkani-Hamed et al. 1996M. Hirouchi, M Tanaka 1998J. Hisano et al. 1999M. Guchait, J. Kalinowski, P. Roy 2002

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R-conserving SUSYR-conserving SUSY1-loop process due to slepton mix1-loop process due to slepton mixResonant effect enhances Resonant effect enhances

the cross section the cross section better than better than

can probe a region can probe a region of parameter space which is allowed of parameter space which is allowed by theτ→eγ results depending by theτ→eγ results depending on the luminosityon the luminosity

Search for Search for 　　 is complementaryis complementarywith the μ→eγwith the μ→eγ 、、 τ→eγ τ→eγ


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LFV in Higgs boson decaysLFV in Higgs boson decays

Direct measurement of LFV Yukawa couplings.Direct measurement of LFV Yukawa couplings.At the LHC, a Higgs boson is expected at a LC.At the LHC, a Higgs boson is expected at a LC.Precision measurement of Higgs parameters will be done Precision measurement of Higgs parameters will be done at the LHC and at a LC. at the LHC and at a LC. To measure Br(h→μτ) , a LC (a Higgs factory) has the aTo measure Br(h→μτ) , a LC (a Higgs factory) has the advantage because of its kinematics (H-strahlung). dvantage because of its kinematics (H-strahlung). At a LC, LFV Yukawa couplings can be well constraineAt a LC, LFV Yukawa couplings can be well constrained in a wide region of parameter space of the 2HDM. d in a wide region of parameter space of the 2HDM. Study in the MSSM and the 2HDM (Study in the MSSM and the 2HDM (Tsumura’s TalkTsumura’s Talk ) )

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Alternative process for search of the Higgs Alternative process for search of the Higgs LFV couplingLFV coupling

At future ν factories (μ colliders) ,At future ν factories (μ colliders) ,

10102020 muons of energy 50 GeV muons of energy 50 GeV

(100-500GeV) can be available. (100-500GeV) can be available.

DISDIS μ μ Ｎ→Ｎ→ ττ ＸＸ processprocess

At a LC At a LC (E(Ecmcm=500GeV, L=10=500GeV, L=103434/cm/cm22/s)/s)

10102222 of 250GeV electrons available. of 250GeV electrons available.

DIS process DIS process ee Ｎ→Ｎ→ ττ ＸＸ process process

μ （e） τ

N

qq

h, H, A

X

A fixed target experiment option of ILCA fixed target experiment option of ILC

M. Sher S.K., Y. Kuno, M. Kuze, T. Ota

S.K., Y. Kuno, M. Kuze, T. Ota

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Enhancement of cross section in SUSYEnhancement of cross section in SUSY

CTEQ6L

Sub-process Sub-process ee-- q →τ q →τ- - qq is proportio is proportional to nal to

the the down-typedown-type quark massquark mass..Probability for the b-quark is larger foProbability for the b-quark is larger for higher energies.r higher energies.For For Ee > 60 GeVEe > 60 GeV, ,

the total cross section is enhanced the total cross section is enhanced due to the due to the b-quark sub-processb-quark sub-process Ee Ee ＝＝ 50 GeV 1050 GeV 10-5 -5 fbfb

100 GeV100 GeV 　　 1010-4 -4 fb fb 250 GeV250 GeV 　　 1010-3-3fbfb

e τ

N

qq

h, H, A

X

Higgs mediated LFV process

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Contribution of the gauge boson mediation

e τ

N

qq

γ ,Z

X

τ→eγτ→eγ 　　 results gives the upper bound results gives the upper bound on the tensor coupling, therefore on on the tensor coupling, therefore on the e N →τXthe e N →τX 　　 cross sectioncross section

Gauge mediated LFV ⇒ 　 No bottom Yukawa enhancement

At high energy DIS e N →τX 　 process is more sensitive to the Higgs mediation than the gauge mediation.

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Number of produced taus Number of produced taus 　　 EeEe ＝＝ 250 GeV, 250 GeV, L =10L =103434 /cm /cm22/s, ⇒/s, ⇒ 　　 10102222 electrons electrons In a SUSY model with |κIn a SUSY model with |κ3131 |^2=0.3×10 |^2=0.3×10-6-6 　　 : : σ=10σ=10-3-3 fb fb 　　 = 2 x 10= 2 x 10-42 -42 cmcm22

NNττ== 　　 ρ Nρ NAA 　　 NNee 　　 σσ

　　 101055 of τleptons are produced of τleptons are produced for for the target of ρ=10 g/cm^2 the target of ρ=10 g/cm^2 　　　　　　　　

Naively, non-observation of the high energy muons froNaively, non-observation of the high energy muons from the tau of the e N → τ X process may improve the cm the tau of the e N → τ X process may improve the current upper limit on the eτΦ couplingurrent upper limit on the eτΦ coupling22 by around 4 ord by around 4 orders of magnitudeers of magnitude

NA=6 x 1023

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High energy muon from tau cay be High energy muon from tau cay be a signala signal

Geometry (picture) ex) target ρ=10g/cmGeometry (picture) ex) target ρ=10g/cm22

BackgroundsBackgrounds Pion punch-throughPion punch-through Muons from Pion decay-in-flightMuons from Pion decay-in-flight Muon from the muon pair production Muon from the muon pair production …………. .

e

μ

τ

Hadron absorber

Muon spectrometer(momentum measurement)

(water)(iron)

eelemag shower

π

Monte Carlo simulation is being done. GEANT4,…Monte Carlo simulation is being done. GEANT4,…

10cm 6-10m

target

SK, Y. Kuno, M. Kuze, T. Ota, T. Takai

dump

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Summary1 Summary1 LFV is a clear signature for physics beyond the SMLFV is a clear signature for physics beyond the SM

μ- e mixing strongly constrained by μ- e mixing strongly constrained by

　　　　　　 μ→eγ, μ-e conversion, ……μ→eγ, μ-e conversion, ……

Collider experiments can be useful to search Collider experiments can be useful to search

τ associated LFV processesτ associated LFV processes..

Various LFV process can be searched at ILC.Various LFV process can be searched at ILC. LFV in LFV in LFV in LFV in LFV in Higgs boson decays LFV in Higgs boson decays LFV in DIS process at the fixed target optionLFV in DIS process at the fixed target option

These can be competitive to LFV searches at (Super) B factories These can be competitive to LFV searches at (Super) B factories

Tsumura’s talk

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Summary 2Summary 2DIS processDIS process e N →τX : e N →τX : Possibility of a fixed target experiment at a LC Possibility of a fixed target experiment at a LC The cross section is enhanced due to the sub-process of HigThe cross section is enhanced due to the sub-process of Hig

gs mediation with sea b-quarks gs mediation with sea b-quarks At a LC with EAt a LC with Ecmcm=500GeV σ⇒=500GeV σ⇒ ＝＝ 1010-3-3 fb fb

L=10L=103434/cm/cm22/s 10⇒/s 10⇒ 2222 electrons available electrons available

10^5 of taus are produced10^5 of taus are produced for ρ=10 g/cm for ρ=10 g/cm22 Non-observation of the signal (high-energy muons) Non-observation of the signal (high-energy muons)

would improve the current limit by several orders. would improve the current limit by several orders. 　　　　 Realistic simulation: work in progress.Realistic simulation: work in progress.

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Angular distribution

eL

τR

θ

Target

Lab-frame

Lab-frame

Higgs mediationHiggs mediation → → 　　 chirality flippedchirality flipped　→　（　→　（ 11 －－ cosθcosθSMSM ）） 22

From theFrom the e eLL beam, beam, ττRR is emitted to the backward direction due to is emitted to the backward direction due to (1 (1 ーー cosθcosθCMCM))22 　　 nature in CM frame. nature in CM frame.

In Lab-frame, tau is emitted forward direction with some PIn Lab-frame, tau is emitted forward direction with some PTT..

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SignalSignal

BackgroundsBackgrounds

usual DISusual DIS

Higgs boson mediationHiggs boson mediation

photon mediationphoton mediation

Different distributionDifferent distribution 　　　　 ⇒　　　　　 ⇒　 BG reduction by EBG reduction by Eττ, θ, θττ 　　 cuts cuts

Shinya KANEMURA 1 Search for Lepton Flavor Violation at the ILC Shinya Kanemura (Osaka Univ.) 8th...

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Transcript of Shinya KANEMURA 1 Search for Lepton Flavor Violation at the ILC Shinya Kanemura (Osaka Univ.) 8th...