Pasquale Di Bari

1
Baryogenesis toward a verdict
LMU, Munich, 13 November 2007

• Pasquale Di Bari
• (INFN, Padova)

2
?CDM a cosmological SM ?
3
Thermal history of the Universe
4
Cosmological puzzles

• Matter - antimatter asymmetry
• Dark matter
• Accelerating Universe
• Inflation

? clash between the SM and ?CDM !
5
Matter-antimatter asymmetry

• Symmetric Universe with matter- anti matter
  domains ? Excluded by CMB cosmic rays
• ) ?B (6.3 0.3) x 10-10 gtgt ?B
  
• Pre-existing ? It conflicts with inflation !
  (Dolgov 97)
• ) dynamical generation (baryogenesis)
• A Standard Model Solution ? ?B ?B too
  low !

CMB
(Sakharov 67)
CMB
SM
New Physics is needed!
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Models of Baryogenesis

• From phase transitions
• - ELECTROWEAK BARYOGENESIS
  (EWBG)
• in the SM
• in the MSSM
• in the nMSSM
• in the NMSSM
• in the 2 Higgs model
• Affleck-Dine
• - at preheating
• - Q-balls
• - .

• From Black Hole evaporation
• Spontaneous Baryogenesis
• From heavy particle decays
• - GUT Baryogenesis
• - LEPTOGENESIS

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Baryogenesis in the SM ?

• All 3 Sakharov conditions are fulfilled in the
  SM
• baryon number violation if T ? 100 GeV,
• CP violation in the quark CKM matrix,
• departure from thermal equilibrium (an arrow of
  time)
• from the expansion of the Universe

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Baryon Number Violation at finite T
(t Hooft 76)
Even though at T 0 baryon number violating
processes are inhibited, at finite T

0 for T ? Tc (unbroken phase)
v(Tc) for T ? T c (broken phase)

• Baryon number violating processes are
  unsuppressed at T ? Tc ? 100 GeV
• Anomalous processes violate lepton number as
  well but preserve B-L !

There can be enough departure from thermal
equilibrium ?
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EWBG in the SM
If the EW phase transition (PT) is 1st order ?
broken phase bubbles nucleate
In the SM the ratio vc/Tc is directly related to
the Higgs mass and only for Mh lt 40 GeV one
can have a strong PT ? EW baryogenesis in the SM
is ruled out by the LEP lower bound Mh ? 114
GeV ! (also not enough CP)
? New Physics is needed!
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EWBG in the MSSM
(Carena, Quiros, Wagner 98)

• Additional bosonic degrees of freedom
  (dominantly the light stop contribution)
• can make the EW phase transition more strongly
  first order if

LEP lower bound

• Notice that there is a tension between the
  strong PT requirement and the LEP
• lower bound on Mh and in particular one has to
  impose 5 ? tan ? ? 10
• In addition there are severe constraints from
  the simultaneous requirement of
• CP violation in the bubble walls (mainly from
  charginos) without generating too
• large electric dipole moment of the electron is
  EWBG still alive ?

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Is EWBG still alive ?

• 3 possible attitudes
• Optimistic Not only it is alive but the allowed
  region in the MSSM
• parameter space, though
  quite constrained, allows also
• to solve another of the
  cosmological puzzles Dark Matter
• (Balazs, Carena, Menon, Morissey,
  Wagner, 05)
• Realistic EWBG in the MSSM has strong
  constraints but these
• can be relaxed within
  other frameworks
• - in the NMSSM
• (Pietroni
  92,Davies et al. 96, Huber and Schmidt 01)
• - in the nMSSM
• (Wagner et al. 04)
• - in left-right symmetric models at B-L
  symmetry breaking
• (Mohapatra and Zhang 92)
• - .
• Pessimistic We need some other mechanism SUSY
  has
• not yet been discovered but
  on the other hand .

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EWBG in the nMSSM
(Menon, Morissey, Wagner04 Balazs, Carena,
Freitas, Wagner et al. 07)

• The ?-problem in the MSSM can be solved
  introducing a singlet
• chiral superfield ? the mass of the (CP-even)
  Higgs boson
• responsible for EWSB can be easily much
  higher than the LEP
• lower bound (mh0 ? 114.4 GeV)
• Discrete symmetries have to be imposed, two
  popular options
• Next-to-MSSM (NMSSM) based on ?3
• nearly-MSSM (nMSSM) based on ?5 or ?7
• The nMSSM is interesting for EWBG because
  strong first order phase
• transition does not require too light Higgs
  and stop masses
• However chargino and Higgs mass parameters are
  required to be in the
• range testable at LHC and ILC
• Constraints from EDMs are still present but
  weaker than in the MSSM
• new experiments will improve current upper
  bound on the electron
• EDM and in many scenarios non zero value is
  expected
• At the same time neutralino is the LSP and
  can be the Dark Matter for
• masses about 30-45 GeV

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Is EWBG still alive ?

• 3 possible attitudes
• Optimistic Not only it is alive but the allowed
  region in the MSSM
• parameter space has
  interesting features also to solve
• another of the
  cosmological puzzles Dark Matter
• (Carena et al. 05)
• Realistic EWBG in the MSSM has strong
  constraints but these
• can be relaxed within
  other frameworks
• - in the NMSSM
• (Pietroni
  92,Davies et al. 96, Huber and Schmidt 01)
• - in the nMSSM
• (Wagner et al. 04)
• - in left-right symmetric models at B-L
  symmetry breaking
• (Mohapatra and Zhang 92)
• - .
• Pessimistic We need some other mechanism SUSY
  has
• not yet been discovered but
  on the other hand .

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Neutrino masses m1 lt m2 lt m3
Tritium ? decay me lt 2.3 eV (Mainz 95 CL)
??0? m?? lt 0.3 1.0 eV (Heidelberg-Moscow
90 CL, similar result by CUORICINO )
using the flat prior (?01) CMBLSS ? mi lt
0.94 eV (WMAPSDSS) CMBLSS Ly? ? mi lt 0.17
eV (Seljak et al.)
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A minimal extension of the SM with right-handed
neutrinos

• 3 limiting cases
• pure Dirac MR 0
• pseudo-Dirac MR ltlt mD
• see-saw limit MR gtgt mD

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See-saw mechanism

• 3 light LH neutrinos
• N?2 heavy RH neutrinos N1,
  N2 ,

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Leptogenesis in a nutshell
(Fukugita,Yanagida 86)
M, mD, m? are complex matrices ? natural
source of CP violation
CP asymmetry
If ?i ? 0 ? a lepton asymmetry is generated
from Ni
decays and partly converted into a
baryon asymmetry by sphaleron processes if
Treh ? 100 GeV !
(Kuzmin,Rubakov,Shaposhnikov, 85)
efficiency factors ? of Ni decaying
out-of-equilibrium
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(Blanchet, PDB 06)
UNFLAVORED REGIME
N1
N1
F
l1
F
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The see-saw orthogonal matrix
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The traditional picture
Assume

• Unflavoured regime
• Semi-hierarchical heavy neutrino spectrum

N1 dominated scenario
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Total CP asymmetry
(Flanz,Paschos,Sarkar95 Covi,Roulet,Vissani96
Buchmüller,Plümacher98)
(Davidson, Ibarra 02 Buchmüller,PDB,Plümacher03
PDB05 )
It does not depend on U !
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Efficiency factor
(Buchmüller,PDB, Plümacher 04)
decay parameter
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Dependence on the initial conditions
(Buchmuller,PDB, Pl umacher 04)
m1? msol
M1?1014 GeV
Neutrino mixing data favor the strong wash-out
regime !
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Neutrino mass bounds
10-6 ( M1 / 1010 GeV)
Upper bound on the absolute neutrino mass scale
(Buchmüller, PDB, Plümacher 02)
0.12 eV
Lower bound on M1 (Davidson, Ibarra
02 Buchmüller, PDB, Plümacher 02)
3x109 GeV
Lower bound on Treh Treh ? 1.5 x 109
GeV (Buchmüller, PDB, Plümacher 04)
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A very hot Universe for leptogenesis ?
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Beyond the minimal picture

• M2 ? M3 ? ?1 ? ? (M1) evaded
• N2-dominated scenario
• beyond the hierarchical limit
• flavor effects

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N2-dominated scenario
(PDB05)
Four things happen simultaneously
For a special choice of the see-saw orthogonal
matrix
?
The lower bound on M1 disappears and is
replaced by a lower bound on M2 that however
still implies a lower bound on Treh !
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Beyond the hierarchical limit
(Pilalftsis 97, Hambye et al 03, Blanchet,PDB
06)
Assume

• partial hierarchy M3 gtgt M2 , M1

• heavy N3 M3 gtgt 1014 GeV

3 Effects play simultaneously a role for ?2 ? 1

For ?2 ? 0.01 (degenerate limit) the first two
effects saturate and
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Flavour effects
(Nardi,Roulet06Abada et al.06Blanchet,PDB06)
Flavour composition
Does it play any role ?
but , for lower values of M1 , ?-Yukawa
interactions,
are fast enough to break the coherent evolution
of the and quantum states projecting
them on the flavour basis within the horizon ?
potentially a fully flavored regime holds!
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Fully flavoured regime
Let us introduce the projectors
(Barbieri,Creminelli,Strumia,Tetradis01)
These 2 terms correspond to 2 different flavour
effects

• In each inverse decay
  the Higgs interacts now with
• incoherent flavour eigenstates ! ? the
  wash-out is reduced and
• 2. In general and
  this produces an additional CP violating
  contribution to the flavoured CP asymmetries

Interestingly one has that now this additional
contribution depends on U !
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In pictures
1)
N1
2)
?
?
N1
?
?
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Fully flavoured regime
Let us introduce the projectors
(Barbieri,Creminelli,Strumia,Tetradis01)
These 2 terms correspond to 2 different flavour
effects

• In each inverse decay
  the Higgs interacts now with
• incoherent flavour eigenstates ! ? the
  wash-out is reduced and
• 2. In general and
  this produces an additional CP violating
  contribution to the flavoured CP asymmetries

Interestingly one has that now this additional
contribution depends on U !
33
(No Transcript)
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Neutrino mass bounds
?
(Abada,Davidson, Losada, Riotto06 Blanchet,
PDB06)
0.12 eV
M1 (GeV)
EXCLUDED
INTERMEDIATE REGIME
Condition of validity of a classic description
in the fully flavored regime
FULLY FLAVORED REGIME
EXCLUDED
EXCLUDED
m1(eV)
Is the fully flavoured regime suitable to
answer the question ?
No ! There is an intermediate regime where a full
quantum kinetic description is necessary !
(Blanchet,PDB,Raffelt 06)
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(Anisimov, Blanchet, PDB, arXiv 0707.3024 )
In the hierarchical limit (M3gtgt M2 gtgt M1 )
In this region the results from the full flavored
regime are expected to undergo severe
corrections that tend to reduce the allowed
region
M1 (GeV)
?1 0 ?2 0 ? -?/2
sin?130.20
Here some minor corrections are also expected
?-leptogenesis represents another
important motivation for a full Quantum
Kinetic description !
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Unflavored vs. flavored leptogenesis
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Can we detect RH neutrinos at LHC ?
Typically lowering the RH neutrino scale at TeV ,
the RH neutrinos decouple and they cannot
be efficiently produced in colliders
Different claimed possibilities to circumvent the
problem

• ? - resonant leptogenesis (Pilaftsis,
  Underwood 05)
• additional gauged U(1)B-L (King,Yanagida 04)

• Going beyond the usual type I see-saw
• leptogenesis with Higgs triplet
• (Ma,Sarkar 00 Hambye,Senjanovic 03
  Rodejohann04 Hambye,Strumia 05)
• leptogenesis with three body decays (Hambye 01)
  
• see-saw with vector fields (Losada,Nardi 07)
• ..

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An exciting duelLeptogenesis vs.
EWBG
1
2
At present

• Neutrino masses discovered
• with correct order-of-magnitude !

• Higher compatibility with
• (SUSY) DM solutions

Wish-list for future

• Higgs boson(s ?) at LHC
• Treheating ? 100 GeV
• No anti-nuclei

• CP violation in neutrino mixing
• ??0?
• SUSY discovery with right features
• - non viable EWBG
• - LFV (eg ? ? e?), EDMs
• - no gravitino problem
• dream heavy RH neutrino detection at LHC
  

• SUSY discovery with right
• features at LHC and ILC
• not too large EDMs
• SUSY DM discovery compatible with EWBG
• (typically neutralino)

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Final remarks

• At present leptogenesis has a clear advantage on
  EWBG neutrino masses have been discovered and
  even in the right range a discovery of CP
  violation in neutrino mixing would represent
  another important success
• EWBG has the nice virtue to be highly predictive
  (therefore also falsifiable) LHC,ILC,DM direct
  searches, EDMs, possible detection of
  gravitational waves at LISA

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True final remarks

• If nothing beyond a SM Higgs will be found, then
  EWBG can hardly survive. This can be regarded as
  a positive test for leptogenesis but also a
  missed opportunity to prove it in particular DM
  and SUSY searches will play a key role
• On the other hand EWBG discovery would kill
  leptogenesis !
• EWBG and Leptogenesis are 2 possible options
  within GUTs and understanding which one is right
  would give us precious information !