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Electroweak Baryogenesis and LC

Yasuhiro Okada (KEK)

8th ACFA LC workshop

July 12, 2005, Daegu, Korea

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Baryon number of Universe

Important interplay between cosmology and particle physics

Three conditions to create baryon number of Universe Baryon number violation C and CP violation Departure from thermal equilibrium One clear reason for physics beyond the Standard

Model.

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Two scenarios B+L violation is enhanced at high temperature in th

e Standard Model. (Weak sphaleron interaction)

Successful Baryon Number Generation (1) B-L generation at temperature above the electroweak phase transition. (ex. Leptogenesis) (2) Baryon number generation at the electroweak phase transition =“Electroweak Baryogenesis”

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Contents

Conditions for electroweak baryogenesis Examples in MSSM, etc. Electroweak baryogenesis and Higgs self-

coupling measurement

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Strong first order phase transition. Expansion of a bubble wall. Various charge flows due to CP violation at the wall. Baryon number violation in the symmetric phase.

Baryon number generation at EW phase transition

Final baryon number depends on what charge asymmetry is generated,how charges are transported in the plasma, the wall velocity, etc.

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Condition of the strong first order transitionThe first order phase transition is needed for a bubble nucl

eation. The sphaleron transition rate should be suppressed in the

broken phase at the critical temperature, in order not to erase the created baryon number.

This condition is expressed as

Strong first order phase transition.

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Finite temperature effective potential in the SM

In the high temperature expansion (m/T <1)

In order to satisfy c/Tc>1, the Higgs mass should be less than 50 GeV, which is much smaller than LEP bound.More accurate calculation confirmed the same conclusion.

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Bosonic loop corrections

Heavy Higgs boson loops in 2 Higgs doublet model

Light stop loops in MSSM

(Fermionic loops are not very effective) Modification of tree level potential

Cubic terms in NMSSM and SUSY with extra U(1)

SM with extra singlet.

SM with dim 6 Higgs potential.

etc. etc.

Possible way out

New particles and/or modification of the Higgs sector is necessary. => Some form of collider signals.

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Electroweak Baryogenesis in MSSM Light right-handed stop (m(stop) < m(top)) is requir

ed for the strong 1st order phase transition

• Sources of new CP violation Stop A term (At) chargino/neutralino mass matrixes ( parameter)

Chargino effect turns out to be dominant source of the baryon number generation

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Required mass spectrum

Right-handed stop (<top mass) LSP neutralino Chargino ( < ~ 200 GeV)

Left-handed stop should be multi TeV ( precision EW and Higgs mass constraints)

Numerical results on baryon number

C.Balazs,M.Carena,A.Menon,D.E.Morrissey, C.E.M.Wagner 2005

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Phenomenological impacts Light right-handed stop whose mass is close to LSP neutralino.Light chargino/neutralino with a complex phase of sin >0.1 => ILC physics

EDM closed to the present bounds

Parameter space allowed by EWBG and EDM

C.Balazs,M.Carena,A.Menon,D.E.Morrissey, C.E.M.Wagner 2005

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Other examplesSUSY U(1)’ model J.Kang, P.Langacker,T.Li, T.Liu,2005

1st order phase transition from SHdHu

SM with a low cut-off

D.Bodeker,L.Fromme,S.J.Huber,M.Seniuch,2005

New CP violation from

M (GeV)

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Higgs self-coupling constant and EWBG Electroweak baryogensis requires a large correction to th

e finite temperature effective potential. The zero temperature potential is also expected to receiv

e a large correction. This will give a measurable impact to the triple Higgs bos

on coupling. We study this connection in 2HDM and MSSM. S.Kaenmura, Y. Okada, E.Senaha, 2004

Cf. An extension to quartic coupling, S.W. Ham and S.K.Oh, 2005 A similar connection in the model with a dim-6 Higgs potential term, C.Grojean,G.Servant, J.D.Wells, 2004

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Two Higgs doublet model

Two cases

12 /tan

Physical Higgs bosons:

Higgs potential

Heavy Higgs boson masses

(1)Decupling case:

(2) Non-decoupling case

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Effective potential in 2HDM

Radiative correction to triple coupling constant (sin() ~1)

Correction to the cubic term in finite temp potential (high temp expansion, M=0)

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mh= 120 GeV mh= 160 GeV

Numerical results on radiative correction to the triple coupling constant(not using high temp expansion)

If we require the strong enough first order phase transition for EWBG,

In MSSM case,

~6%

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Triple Higgs coupling measurement at ILC

Expected efficiency is 40 %, S.Yamashita et.al, LCWS 04.

Y. Yasui, et.al. GLC report R. Belusevic and G.Jikia 2004

HH

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Summary

Electroweak baryogenesis offers an important connection between cosmology and particle physics.

Successful baryon-number generation at the electroweak phase transition requires new physics related to the Higgs sector.

Ex. Correction to the Higgs potential, new particles with a sizable interaction to the Higgs field

New particles and new interactions relevant to the electroweak baryogensis should exist close to the Higgs mass scale.

ILC will play an important role to test this scenario, by exploring new particles/interactions including possible new sources of CP violation.