electroweak baryogenesis and lc
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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.
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