particle physics and cosmology baryon asymmetry
Post on 19-Dec-2015
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dimensionless inverse dimensionless inverse temperaturetemperature
dimensionlessdimensionlesstime variable time variable in units ofin units ofparticle mass m particle mass m
m : particle massm : particle mass
small x : particle is relativistic x<3small x : particle is relativistic x<3large x : particle is non-relativistic x>3large x : particle is non-relativistic x>3
cold relic abundance ,cold relic abundance ,mass and cross sectionmass and cross section
mm(m,(m,σσ
AA))
inversely proportional to cross section ,inversely proportional to cross section , plus logarithmic dependence of xplus logarithmic dependence of xff
baryon relics in baryon relics in baryon symmetric Universebaryon symmetric Universe
observed : Y = observed : Y = ηη ≈ 10 ≈ 10 -10-10
A.CocA.Coc
Abundancies of Abundancies of primordialprimordiallight elementslight elementsfrom from nucleosynthesisnucleosynthesis
primordial abundances primordial abundances for three GUT modelsfor three GUT models
T.Dent,T.Dent,S.Stern,…S.Stern,…
present present observatioobservations : 1ns : 1σσ
HeHe
DD
LiLi
conserved baryon conserved baryon asymmetryasymmetry
no baryon number violating processes inno baryon number violating processes instandard model of particle physics at energystandard model of particle physics at energybelow 1 GeVbelow 1 GeV
baryon asymmetry must exist at T = 1 GeV baryon asymmetry must exist at T = 1 GeV
baryon number violation in baryon number violation in standard modelstandard model
baryon number is global symmetry of baryon number is global symmetry of interactions in the standard modelinteractions in the standard model
violated by quantum anomaly violated by quantum anomaly ( no ( no anomalies possible for local symmetries : anomalies possible for local symmetries : corresponding charge , like electric corresponding charge , like electric charge , exactly conserved )charge , exactly conserved )
sphaleron processes generate strong sphaleron processes generate strong baryon number violating processes at baryon number violating processes at temperatures above 100-200 GeVtemperatures above 100-200 GeV
baryon number violation in baryon number violation in standard modelstandard model
no chemical potential for baryon numberno chemical potential for baryon number
thermal equilibrium in thermal equilibrium in absence of chemical absence of chemical
potentialpotential
Sakharov’s conditions forSakharov’s conditions forbaryogenesisbaryogenesis
1)1) baryon number violation baryon number violation interactionsinteractions
2)2) charge conjugation violating charge conjugation violating interactionsinteractions
3)3) CP – violating interactionsCP – violating interactions
4)4) non – equilibrium processnon – equilibrium process
baryon number violating baryon number violating processprocess
in Grand Unified Theories in Grand Unified Theories ( GUT )( GUT )
baryon number violating baryon number violating processprocess
in Grand Unified Theories in Grand Unified Theories ( GUT )( GUT )
not good enough :not good enough :
B asymmetry will be washed out later B asymmetry will be washed out later by sphaleron processesby sphaleron processes
no B-L asymmetry is producedno B-L asymmetry is produced
leptogenesisleptogenesis
B – L is conserved quantum B – L is conserved quantum number innumber in
standard modelstandard model sphaleron processes transmute lepton sphaleron processes transmute lepton
asymmetry into baryon asymmetryasymmetry into baryon asymmetry a fraction of primordial B-L asymmetry a fraction of primordial B-L asymmetry
appears as baryon asymmetryappears as baryon asymmetry
primordial asymmetry protected from primordial asymmetry protected from wash out by sphaleron processeswash out by sphaleron processes
( B-L )( B-L )
leptogenesisleptogenesis
non – equilibrium decay of heavy non – equilibrium decay of heavy neutrinosneutrinos
non – equilibrium production after non – equilibrium production after inflation during entropy production inflation during entropy production of the Universeof the Universe
baryogenesis during baryogenesis during electroweak phase electroweak phase
transition ?transition ?
Sakharov’s conditions forSakharov’s conditions forbaryogenesis during baryogenesis during electroweak phase electroweak phase
transitiontransition
1)1) baryon number violation interactions ☺baryon number violation interactions ☺
2)2) charge conjugation violating charge conjugation violating interactions ☺interactions ☺
3)3) CP – violating interactions ☺CP – violating interactions ☺
4)4) non – equilibrium process ☺non – equilibrium process ☺
baryogenesis during baryogenesis during electroweak phase electroweak phase
transitiontransition strongly first order electroweak strongly first order electroweak
phase transition can generate baryon phase transition can generate baryon asymmetry if CP violation is asymmetry if CP violation is sufficiently strong sufficiently strong
no efficient baryogenesis for weak no efficient baryogenesis for weak first order phase transition, second first order phase transition, second order phase transition or crossoverorder phase transition or crossover
presumably too little CP violation in presumably too little CP violation in SM ( not definitely settled )SM ( not definitely settled )
electroweak “phase electroweak “phase transition “transition “
in standard model is in standard model is crossover !crossover !
perhaps strong first order transition in perhaps strong first order transition in supersymmetric extensions of standard model supersymmetric extensions of standard model
standard model of particle standard model of particle physics and cosmologyphysics and cosmology
no candidate for dark matterno candidate for dark matter no baryon asymmetryno baryon asymmetry no massive neutrinosno massive neutrinos